- 根目录:
- fs
- locks.c
/*
* linux/fs/locks.c
*
* Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
* Doug Evans (dje@spiff.uucp), August 07, 1992
*
* Deadlock detection added.
* FIXME: one thing isn't handled yet:
* - mandatory locks (requires lots of changes elsewhere)
* Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
*
* Miscellaneous edits, and a total rewrite of posix_lock_file() code.
* Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
*
* Converted file_lock_table to a linked list from an array, which eliminates
* the limits on how many active file locks are open.
* Chad Page (pageone@netcom.com), November 27, 1994
*
* Removed dependency on file descriptors. dup()'ed file descriptors now
* get the same locks as the original file descriptors, and a close() on
* any file descriptor removes ALL the locks on the file for the current
* process. Since locks still depend on the process id, locks are inherited
* after an exec() but not after a fork(). This agrees with POSIX, and both
* BSD and SVR4 practice.
* Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
*
* Scrapped free list which is redundant now that we allocate locks
* dynamically with kmalloc()/kfree().
* Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
*
* Implemented two lock personalities - FL_FLOCK and FL_POSIX.
*
* FL_POSIX locks are created with calls to fcntl() and lockf() through the
* fcntl() system call. They have the semantics described above.
*
* FL_FLOCK locks are created with calls to flock(), through the flock()
* system call, which is new. Old C libraries implement flock() via fcntl()
* and will continue to use the old, broken implementation.
*
* FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
* with a file pointer (filp). As a result they can be shared by a parent
* process and its children after a fork(). They are removed when the last
* file descriptor referring to the file pointer is closed (unless explicitly
* unlocked).
*
* FL_FLOCK locks never deadlock, an existing lock is always removed before
* upgrading from shared to exclusive (or vice versa). When this happens
* any processes blocked by the current lock are woken up and allowed to
* run before the new lock is applied.
* Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
*
* Removed some race conditions in flock_lock_file(), marked other possible
* races. Just grep for FIXME to see them.
* Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
*
* Addressed Dmitry's concerns. Deadlock checking no longer recursive.
* Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
* once we've checked for blocking and deadlocking.
* Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
*
* Initial implementation of mandatory locks. SunOS turned out to be
* a rotten model, so I implemented the "obvious" semantics.
* See 'Documentation/filesystems/mandatory-locking.txt' for details.
* Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
*
* Don't allow mandatory locks on mmap()'ed files. Added simple functions to
* check if a file has mandatory locks, used by mmap(), open() and creat() to
* see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
* Manual, Section 2.
* Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
*
* Tidied up block list handling. Added '/proc/locks' interface.
* Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
*
* Fixed deadlock condition for pathological code that mixes calls to
* flock() and fcntl().
* Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
*
* Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
* for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
* guarantee sensible behaviour in the case where file system modules might
* be compiled with different options than the kernel itself.
* Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
*
* Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
* (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
* Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
*
* Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
* locks. Changed process synchronisation to avoid dereferencing locks that
* have already been freed.
* Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
*
* Made the block list a circular list to minimise searching in the list.
* Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
*
* Made mandatory locking a mount option. Default is not to allow mandatory
* locking.
* Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
*
* Some adaptations for NFS support.
* Olaf Kirch (okir@monad.swb.de), Dec 1996,
*
* Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
* Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
*
* Use slab allocator instead of kmalloc/kfree.
* Use generic list implementation from <linux/list.h>.
* Sped up posix_locks_deadlock by only considering blocked locks.
* Matthew Wilcox <willy@debian.org>, March, 2000.
*
* Leases and LOCK_MAND
* Matthew Wilcox <willy@debian.org>, June, 2000.
* Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
*/
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
#include <linux/hashtable.h>
#include <linux/percpu.h>
#include <linux/lglock.h>
#include <asm/uaccess.h>
#define IS_POSIX(fl) (fl->fl_flags & FL_POSIX)
#define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK)
#define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG))
static bool lease_breaking(struct file_lock *fl)
{
return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
}
static int target_leasetype(struct file_lock *fl)
{
if (fl->fl_flags & FL_UNLOCK_PENDING)
return F_UNLCK;
if (fl->fl_flags & FL_DOWNGRADE_PENDING)
return F_RDLCK;
return fl->fl_type;
}
int leases_enable = 1;
int lease_break_time = 45;
#define for_each_lock(inode, lockp) \
for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
/*
* The global file_lock_list is only used for displaying /proc/locks, so we
* keep a list on each CPU, with each list protected by its own spinlock via
* the file_lock_lglock. Note that alterations to the list also require that
* the relevant i_lock is held.
*/
DEFINE_STATIC_LGLOCK(file_lock_lglock);
static DEFINE_PER_CPU(struct hlist_head, file_lock_list);
/*
* The blocked_hash is used to find POSIX lock loops for deadlock detection.
* It is protected by blocked_lock_lock.
*
* We hash locks by lockowner in order to optimize searching for the lock a
* particular lockowner is waiting on.
*
* FIXME: make this value scale via some heuristic? We generally will want more
* buckets when we have more lockowners holding locks, but that's a little
* difficult to determine without knowing what the workload will look like.
*/
#define BLOCKED_HASH_BITS 7
static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
/*
* This lock protects the blocked_hash. Generally, if you're accessing it, you
* want to be holding this lock.
*
* In addition, it also protects the fl->fl_block list, and the fl->fl_next
* pointer for file_lock structures that are acting as lock requests (in
* contrast to those that are acting as records of acquired locks).
*
* Note that when we acquire this lock in order to change the above fields,
* we often hold the i_lock as well. In certain cases, when reading the fields
* protected by this lock, we can skip acquiring it iff we already hold the
* i_lock.
*
* In particular, adding an entry to the fl_block list requires that you hold
* both the i_lock and the blocked_lock_lock (acquired in that order). Deleting
* an entry from the list however only requires the file_lock_lock.
*/
static DEFINE_SPINLOCK(blocked_lock_lock);
static struct kmem_cache *filelock_cache __read_mostly;
static void locks_init_lock_heads(struct file_lock *fl)
{
INIT_HLIST_NODE(&fl->fl_link);
INIT_LIST_HEAD(&fl->fl_block);
init_waitqueue_head(&fl->fl_wait);
}
/* Allocate an empty lock structure. */
struct file_lock *locks_alloc_lock(void)
{
struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
if (fl)
locks_init_lock_heads(fl);
return fl;
}
EXPORT_SYMBOL_GPL(locks_alloc_lock);
void locks_release_private(struct file_lock *fl)
{
if (fl->fl_ops) {
if (fl->fl_ops->fl_release_private)
fl->fl_ops->fl_release_private(fl);
fl->fl_ops = NULL;
}
fl->fl_lmops = NULL;
}
EXPORT_SYMBOL_GPL(locks_release_private);
/* Free a lock which is not in use. */
void locks_free_lock(struct file_lock *fl)
{
BUG_ON(waitqueue_active(&fl->fl_wait));
BUG_ON(!list_empty(&fl->fl_block));
BUG_ON(!hlist_unhashed(&fl->fl_link));
locks_release_private(fl);
kmem_cache_free(filelock_cache, fl);
}
EXPORT_SYMBOL(locks_free_lock);
void locks_init_lock(struct file_lock *fl)
{
memset(fl, 0, sizeof(struct file_lock));
locks_init_lock_heads(fl);
}
EXPORT_SYMBOL(locks_init_lock);
static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
{
if (fl->fl_ops) {
if (fl->fl_ops->fl_copy_lock)
fl->fl_ops->fl_copy_lock(new, fl);
new->fl_ops = fl->fl_ops;
}
if (fl->fl_lmops)
new->fl_lmops = fl->fl_lmops;
}
/*
* Initialize a new lock from an existing file_lock structure.
*/
void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
{
new->fl_owner = fl->fl_owner;
new->fl_pid = fl->fl_pid;
new->fl_file = NULL;
new->fl_flags = fl->fl_flags;
new->fl_type = fl->fl_type;
new->fl_start = fl->fl_start;
new->fl_end = fl->fl_end;
new->fl_ops = NULL;
new->fl_lmops = NULL;
}
EXPORT_SYMBOL(__locks_copy_lock);
void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
locks_release_private(new);
__locks_copy_lock(new, fl);
new->fl_file = fl->fl_file;
new->fl_ops = fl->fl_ops;
new->fl_lmops = fl->fl_lmops;
locks_copy_private(new, fl);
}
EXPORT_SYMBOL(locks_copy_lock);
static inline int flock_translate_cmd(int cmd) {
if (cmd & LOCK_MAND)
return cmd & (LOCK_MAND | LOCK_RW);
switch (cmd) {
case LOCK_SH:
return F_RDLCK;
case LOCK_EX:
return F_WRLCK;
case LOCK_UN:
return F_UNLCK;
}
return -EINVAL;
}
/* Fill in a file_lock structure with an appropriate FLOCK lock. */
static int flock_make_lock(struct file *filp, struct file_lock **lock,
unsigned int cmd)
{
struct file_lock *fl;
int type = flock_translate_cmd(cmd);
if (type < 0)
return type;
fl = locks_alloc_lock();
if (fl == NULL)
return -ENOMEM;
fl->fl_file = filp;
fl->fl_pid = current->tgid;
fl->fl_flags = FL_FLOCK;
fl->fl_type = type;
fl->fl_end = OFFSET_MAX;
*lock = fl;
return 0;
}
static int assign_type(struct file_lock *fl, long type)
{
switch (type) {
case F_RDLCK:
case F_WRLCK:
case F_UNLCK:
fl->fl_type = type;
break;
default:
return -EINVAL;
}
return 0;
}
/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
* style lock.
*/
static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock *l)
{
off_t start, end;
switch (l->l_whence) {
case SEEK_SET:
start = 0;
break;
case SEEK_CUR:
start = filp->f_pos;
break;
case SEEK_END:
start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
/* POSIX-1996 leaves the case l->l_len < 0 undefined;
POSIX-2001 defines it. */
start += l->l_start;
if (start < 0)
return -EINVAL;
fl->fl_end = OFFSET_MAX;
if (l->l_len > 0) {
end = start + l->l_len - 1;
fl->fl_end = end;
} else if (l->l_len < 0) {
end = start - 1;
fl->fl_end = end;
start += l->l_len;
if (start < 0)
return -EINVAL;
}
fl->fl_start = start; /* we record the absolute position */
if (fl->fl_end < fl->fl_start)
return -EOVERFLOW;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
}
#if BITS_PER_LONG == 32
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock64 *l)
{
loff_t start;
switch (l->l_whence) {
case SEEK_SET:
start = 0;
break;
case SEEK_CUR:
start = filp->f_pos;
break;
case SEEK_END:
start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
start += l->l_start;
if (start < 0)
return -EINVAL;
fl->fl_end = OFFSET_MAX;
if (l->l_len > 0) {
fl->fl_end = start + l->l_len - 1;
} else if (l->l_len < 0) {
fl->fl_end = start - 1;
start += l->l_len;
if (start < 0)
return -EINVAL;
}
fl->fl_start = start; /* we record the absolute position */
if (fl->fl_end < fl->fl_start)
return -EOVERFLOW;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
}
#endif
/* default lease lock manager operations */
static void lease_break_callback(struct file_lock *fl)
{
kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
}
static const struct lock_manager_operations lease_manager_ops = {
.lm_break = lease_break_callback,
.lm_change = lease_modify,
};
/*
* Initialize a lease, use the default lock manager operations
*/
static int lease_init(struct file *filp, long type, struct file_lock *fl)
{
if (assign_type(fl, type) != 0)
return -EINVAL;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_LEASE;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
fl->fl_ops = NULL;
fl->fl_lmops = &lease_manager_ops;
return 0;
}
/* Allocate a file_lock initialised to this type of lease */
static struct file_lock *lease_alloc(struct file *filp, long type)
{
struct file_lock *fl = locks_alloc_lock();
int error = -ENOMEM;
if (fl == NULL)
return ERR_PTR(error);
error = lease_init(filp, type, fl);
if (error) {
locks_free_lock(fl);
return ERR_PTR(error);
}
return fl;
}
/* Check if two locks overlap each other.
*/
static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
{
return ((fl1->fl_end >= fl2->fl_start) &&
(fl2->fl_end >= fl1->fl_start));
}
/*
* Check whether two locks have the same owner.
*/
static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
return fl2->fl_lmops == fl1->fl_lmops &&
fl1->fl_lmops->lm_compare_owner(fl1, fl2);
return fl1->fl_owner == fl2->fl_owner;
}
/* Must be called with the i_lock held! */
static inline void
locks_insert_global_locks(struct file_lock *fl)
{
lg_local_lock(&file_lock_lglock);
fl->fl_link_cpu = smp_processor_id();
hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list));
lg_local_unlock(&file_lock_lglock);
}
/* Must be called with the i_lock held! */
static inline void
locks_delete_global_locks(struct file_lock *fl)
{
/*
* Avoid taking lock if already unhashed. This is safe since this check
* is done while holding the i_lock, and new insertions into the list
* also require that it be held.
*/
if (hlist_unhashed(&fl->fl_link))
return;
lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu);
hlist_del_init(&fl->fl_link);
lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu);
}
static unsigned long
posix_owner_key(struct file_lock *fl)
{
if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
return fl->fl_lmops->lm_owner_key(fl);
return (unsigned long)fl->fl_owner;
}
static inline void
locks_insert_global_blocked(struct file_lock *waiter)
{
hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
}
static inline void
locks_delete_global_blocked(struct file_lock *waiter)
{
hash_del(&waiter->fl_link);
}
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
*
* Must be called with blocked_lock_lock held.
*/
static void __locks_delete_block(struct file_lock *waiter)
{
locks_delete_global_blocked(waiter);
list_del_init(&waiter->fl_block);
waiter->fl_next = NULL;
}
static void locks_delete_block(struct file_lock *waiter)
{
spin_lock(&blocked_lock_lock);
__locks_delete_block(waiter);
spin_unlock(&blocked_lock_lock);
}
/* Insert waiter into blocker's block list.
* We use a circular list so that processes can be easily woken up in
* the order they blocked. The documentation doesn't require this but
* it seems like the reasonable thing to do.
*
* Must be called with both the i_lock and blocked_lock_lock held. The fl_block
* list itself is protected by the file_lock_list, but by ensuring that the
* i_lock is also held on insertions we can avoid taking the blocked_lock_lock
* in some cases when we see that the fl_block list is empty.
*/
static void __locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
BUG_ON(!list_empty(&waiter->fl_block));
waiter->fl_next = blocker;
list_add_tail(&waiter->fl_block, &blocker->fl_block);
if (IS_POSIX(blocker))
locks_insert_global_blocked(waiter);
}
/* Must be called with i_lock held. */
static void locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
spin_lock(&blocked_lock_lock);
__locks_insert_block(blocker, waiter);
spin_unlock(&blocked_lock_lock);
}
/*
* Wake up processes blocked waiting for blocker.
*
* Must be called with the inode->i_lock held!
*/
static void locks_wake_up_blocks(struct file_lock *blocker)
{
/*
* Avoid taking global lock if list is empty. This is safe since new
* blocked requests are only added to the list under the i_lock, and
* the i_lock is always held here. Note that removal from the fl_block
* list does not require the i_lock, so we must recheck list_empty()
* after acquiring the blocked_lock_lock.
*/
if (list_empty(&blocker->fl_block))
return;
spin_lock(&blocked_lock_lock);
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter;
waiter = list_first_entry(&blocker->fl_block,
struct file_lock, fl_block);
__locks_delete_block(waiter);
if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
waiter->fl_lmops->lm_notify(waiter);
else
wake_up(&waiter->fl_wait);
}
spin_unlock(&blocked_lock_lock);
}
/* Insert file lock fl into an inode's lock list at the position indicated
* by pos. At the same time add the lock to the global file lock list.
*
* Must be called with the i_lock held!
*/
static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
{
fl->fl_nspid = get_pid(task_tgid(current));
/* insert into file's list */
fl->fl_next = *pos;
*pos = fl;
locks_insert_global_locks(fl);
}
/*
* Delete a lock and then free it.
* Wake up processes that are blocked waiting for this lock,
* notify the FS that the lock has been cleared and
* finally free the lock.
*
* Must be called with the i_lock held!
*/
static void locks_delete_lock(struct file_lock **thisfl_p)
{
struct file_lock *fl = *thisfl_p;
locks_delete_global_locks(fl);
*thisfl_p = fl->fl_next;
fl->fl_next = NULL;
if (fl->fl_nspid) {
put_pid(fl->fl_nspid);
fl->fl_nspid = NULL;
}
locks_wake_up_blocks(fl);
locks_free_lock(fl);
}
/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
* checks for shared/exclusive status of overlapping locks.
*/
static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
if (sys_fl->fl_type == F_WRLCK)
return 1;
if (caller_fl->fl_type == F_WRLCK)
return 1;
return 0;
}
/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
* checking before calling the locks_conflict().
*/
static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
/* POSIX locks owned by the same process do not conflict with
* each other.
*/
if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
return (0);
/* Check whether they overlap */
if (!locks_overlap(caller_fl, sys_fl))
return 0;
return (locks_conflict(caller_fl, sys_fl));
}
/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
* checking before calling the locks_conflict().
*/
static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
{
/* FLOCK locks referring to the same filp do not conflict with
* each other.
*/
if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
return (0);
if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
return 0;
return (locks_conflict(caller_fl, sys_fl));
}
void
posix_test_lock(struct file *filp, struct file_lock *fl)
{
struct file_lock *cfl;
struct inode *inode = file_inode(filp);
spin_lock(&inode->i_lock);
for (cfl = file_inode(filp)->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
continue;
if (posix_locks_conflict(fl, cfl))
break;
}
if (cfl) {
__locks_copy_lock(fl, cfl);
if (cfl->fl_nspid)
fl->fl_pid = pid_vnr(cfl->fl_nspid);
} else
fl->fl_type = F_UNLCK;
spin_unlock(&inode->i_lock);
return;
}
EXPORT_SYMBOL(posix_test_lock);
/*
* Deadlock detection:
*
* We attempt to detect deadlocks that are due purely to posix file
* locks.
*
* We assume that a task can be waiting for at most one lock at a time.
* So for any acquired lock, the process holding that lock may be
* waiting on at most one other lock. That lock in turns may be held by
* someone waiting for at most one other lock. Given a requested lock
* caller_fl which is about to wait for a conflicting lock block_fl, we
* follow this chain of waiters to ensure we are not about to create a
* cycle.
*
* Since we do this before we ever put a process to sleep on a lock, we
* are ensured that there is never a cycle; that is what guarantees that
* the while() loop in posix_locks_deadlock() eventually completes.
*
* Note: the above assumption may not be true when handling lock
* requests from a broken NFS client. It may also fail in the presence
* of tasks (such as posix threads) sharing the same open file table.
*
* To handle those cases, we just bail out after a few iterations.
*/
#define MAX_DEADLK_ITERATIONS 10
/* Find a lock that the owner of the given block_fl is blocking on. */
static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
{
struct file_lock *fl;
hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
if (posix_same_owner(fl, block_fl))
return fl->fl_next;
}
return NULL;
}
/* Must be called with the blocked_lock_lock held! */
static int posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
int i = 0;
while ((block_fl = what_owner_is_waiting_for(block_fl))) {
if (i++ > MAX_DEADLK_ITERATIONS)
return 0;
if (posix_same_owner(caller_fl, block_fl))
return 1;
}
return 0;
}
/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
* after any leases, but before any posix locks.
*
* Note that if called with an FL_EXISTS argument, the caller may determine
* whether or not a lock was successfully freed by testing the return
* value for -ENOENT.
*/
static int flock_lock_file(struct file *filp, struct file_lock *request)
{
struct file_lock *new_fl = NULL;
struct file_lock **before;
struct inode * inode = file_inode(filp);
int error = 0;
int found = 0;
if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
new_fl = locks_alloc_lock();
if (!new_fl)
return -ENOMEM;
}
spin_lock(&inode->i_lock);
if (request->fl_flags & FL_ACCESS)
goto find_conflict;
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (IS_POSIX(fl))
break;
if (IS_LEASE(fl))
continue;
if (filp != fl->fl_file)
continue;
if (request->fl_type == fl->fl_type)
goto out;
found = 1;
locks_delete_lock(before);
break;
}
if (request->fl_type == F_UNLCK) {
if ((request->fl_flags & FL_EXISTS) && !found)
error = -ENOENT;
goto out;
}
/*
* If a higher-priority process was blocked on the old file lock,
* give it the opportunity to lock the file.
*/
if (found) {
spin_unlock(&inode->i_lock);
cond_resched();
spin_lock(&inode->i_lock);
}
find_conflict:
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (IS_POSIX(fl))
break;
if (IS_LEASE(fl))
continue;
if (!flock_locks_conflict(request, fl))
continue;
error = -EAGAIN;
if (!(request->fl_flags & FL_SLEEP))
goto out;
error = FILE_LOCK_DEFERRED;
locks_insert_block(fl, request);
goto out;
}
if (request->fl_flags & FL_ACCESS)
goto out;
locks_copy_lock(new_fl, request);
locks_insert_lock(before, new_fl);
new_fl = NULL;
error = 0;
out:
spin_unlock(&inode->i_lock);
if (new_fl)
locks_free_lock(new_fl);
return error;
}
static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
{
struct file_lock *fl;
struct file_lock *new_fl = NULL;
struct file_lock *new_fl2 = NULL;
struct file_lock *left = NULL;
struct file_lock *right = NULL;
struct file_lock **before;
int error;
bool added = false;
/*
* We may need two file_lock structures for this operation,
* so we get them in advance to avoid races.
*
* In some cases we can be sure, that no new locks will be needed
*/
if (!(request->fl_flags & FL_ACCESS) &&
(request->fl_type != F_UNLCK ||
request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
new_fl = locks_alloc_lock();
new_fl2 = locks_alloc_lock();
}
spin_lock(&inode->i_lock);
/*
* New lock request. Walk all POSIX locks and look for conflicts. If
* there are any, either return error or put the request on the
* blocker's list of waiters and the global blocked_hash.
*/
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
fl = *before;
if (!IS_POSIX(fl))
continue;
if (!posix_locks_conflict(request, fl))
continue;
if (conflock)
__locks_copy_lock(conflock, fl);
error = -EAGAIN;
if (!(request->fl_flags & FL_SLEEP))
goto out;
/*
* Deadlock detection and insertion into the blocked
* locks list must be done while holding the same lock!
*/
error = -EDEADLK;
spin_lock(&blocked_lock_lock);
if (likely(!posix_locks_deadlock(request, fl))) {
error = FILE_LOCK_DEFERRED;
__locks_insert_block(fl, request);
}
spin_unlock(&blocked_lock_lock);
goto out;
}
}
/* If we're just looking for a conflict, we're done. */
error = 0;
if (request->fl_flags & FL_ACCESS)
goto out;
/*
* Find the first old lock with the same owner as the new lock.
*/
before = &inode->i_flock;
/* First skip locks owned by other processes. */
while ((fl = *before) && (!IS_POSIX(fl) ||
!posix_same_owner(request, fl))) {
before = &fl->fl_next;
}
/* Process locks with this owner. */
while ((fl = *before) && posix_same_owner(request, fl)) {
/* Detect adjacent or overlapping regions (if same lock type)
*/
if (request->fl_type == fl->fl_type) {
/* In all comparisons of start vs end, use
* "start - 1" rather than "end + 1". If end
* is OFFSET_MAX, end + 1 will become negative.
*/
if (fl->fl_end < request->fl_start - 1)
goto next_lock;
/* If the next lock in the list has entirely bigger
* addresses than the new one, insert the lock here.
*/
if (fl->fl_start - 1 > request->fl_end)
break;
/* If we come here, the new and old lock are of the
* same type and adjacent or overlapping. Make one
* lock yielding from the lower start address of both
* locks to the higher end address.
*/
if (fl->fl_start > request->fl_start)
fl->fl_start = request->fl_start;
else
request->fl_start = fl->fl_start;
if (fl->fl_end < request->fl_end)
fl->fl_end = request->fl_end;
else
request->fl_end = fl->fl_end;
if (added) {
locks_delete_lock(before);
continue;
}
request = fl;
added = true;
}
else {
/* Processing for different lock types is a bit
* more complex.
*/
if (fl->fl_end < request->fl_start)
goto next_lock;
if (fl->fl_start > request->fl_end)
break;
if (request->fl_type == F_UNLCK)
added = true;
if (fl->fl_start < request->fl_start)
left = fl;
/* If the next lock in the list has a higher end
* address than the new one, insert the new one here.
*/
if (fl->fl_end > request->fl_end) {
right = fl;
break;
}
if (fl->fl_start >= request->fl_start) {
/* The new lock completely replaces an old
* one (This may happen several times).
*/
if (added) {
locks_delete_lock(before);
continue;
}
/* Replace the old lock with the new one.
* Wake up anybody waiting for the old one,
* as the change in lock type might satisfy
* their needs.
*/
locks_wake_up_blocks(fl);
fl->fl_start = request->fl_start;
fl->fl_end = request->fl_end;
fl->fl_type = request->fl_type;
locks_release_private(fl);
locks_copy_private(fl, request);
request = fl;
added = true;
}
}
/* Go on to next lock.
*/
next_lock:
before = &fl->fl_next;
}
/*
* The above code only modifies existing locks in case of merging or
* replacing. If new lock(s) need to be inserted all modifications are
* done below this, so it's safe yet to bail out.
*/
error = -ENOLCK; /* "no luck" */
if (right && left == right && !new_fl2)
goto out;
error = 0;
if (!added) {
if (request->fl_type == F_UNLCK) {
if (request->fl_flags & FL_EXISTS)
error = -ENOENT;
goto out;
}
if (!new_fl) {
error = -ENOLCK;
goto out;
}
locks_copy_lock(new_fl, request);
locks_insert_lock(before, new_fl);
new_fl = NULL;
}
if (right) {
if (left == right) {
/* The new lock breaks the old one in two pieces,
* so we have to use the second new lock.
*/
left = new_fl2;
new_fl2 = NULL;
locks_copy_lock(left, right);
locks_insert_lock(before, left);
}
right->fl_start = request->fl_end + 1;
locks_wake_up_blocks(right);
}
if (left) {
left->fl_end = request->fl_start - 1;
locks_wake_up_blocks(left);
}
out:
spin_unlock(&inode->i_lock);
/*
* Free any unused locks.
*/
if (new_fl)
locks_free_lock(new_fl);
if (new_fl2)
locks_free_lock(new_fl2);
return error;
}
/**
* posix_lock_file - Apply a POSIX-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
* @conflock: Place to return a copy of the conflicting lock, if found.
*
* Add a POSIX style lock to a file.
* We merge adjacent & overlapping locks whenever possible.
* POSIX locks are sorted by owner task, then by starting address
*
* Note that if called with an FL_EXISTS argument, the caller may determine
* whether or not a lock was successfully freed by testing the return
* value for -ENOENT.
*/
int posix_lock_file(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
return __posix_lock_file(file_inode(filp), fl, conflock);
}
EXPORT_SYMBOL(posix_lock_file);
/**
* posix_lock_file_wait - Apply a POSIX-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
*
* Add a POSIX style lock to a file.
* We merge adjacent & overlapping locks whenever possible.
* POSIX locks are sorted by owner task, then by starting address
*/
int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
{
int error;
might_sleep ();
for (;;) {
error = posix_lock_file(filp, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
if (!error)
continue;
locks_delete_block(fl);
break;
}
return error;
}
EXPORT_SYMBOL(posix_lock_file_wait);
/**
* locks_mandatory_locked - Check for an active lock
* @inode: the file to check
*
* Searches the inode's list of locks to find any POSIX locks which conflict.
* This function is called from locks_verify_locked() only.
*/
int locks_mandatory_locked(struct inode *inode)
{
fl_owner_t owner = current->files;
struct file_lock *fl;
/*
* Search the lock list for this inode for any POSIX locks.
*/
spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!IS_POSIX(fl))
continue;
if (fl->fl_owner != owner)
break;
}
spin_unlock(&inode->i_lock);
return fl ? -EAGAIN : 0;
}
/**
* locks_mandatory_area - Check for a conflicting lock
* @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
* for shared
* @inode: the file to check
* @filp: how the file was opened (if it was)
* @offset: start of area to check
* @count: length of area to check
*
* Searches the inode's list of locks to find any POSIX locks which conflict.
* This function is called from rw_verify_area() and
* locks_verify_truncate().
*/
int locks_mandatory_area(int read_write, struct inode *inode,
struct file *filp, loff_t offset,
size_t count)
{
struct file_lock fl;
int error;
locks_init_lock(&fl);
fl.fl_owner = current->files;
fl.fl_pid = current->tgid;
fl.fl_file = filp;
fl.fl_flags = FL_POSIX | FL_ACCESS;
if (filp && !(filp->f_flags & O_NONBLOCK))
fl.fl_flags |= FL_SLEEP;
fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
fl.fl_start = offset;
fl.fl_end = offset + count - 1;
for (;;) {
error = __posix_lock_file(inode, &fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
if (!error) {
/*
* If we've been sleeping someone might have
* changed the permissions behind our back.
*/
if (__mandatory_lock(inode))
continue;
}
locks_delete_block(&fl);
break;
}
return error;
}
EXPORT_SYMBOL(locks_mandatory_area);
static void lease_clear_pending(struct file_lock *fl, int arg)
{
switch (arg) {
case F_UNLCK:
fl->fl_flags &= ~FL_UNLOCK_PENDING;
/* fall through: */
case F_RDLCK:
fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
}
}
/* We already had a lease on this file; just change its type */
int lease_modify(struct file_lock **before, int arg)
{
struct file_lock *fl = *before;
int error = assign_type(fl, arg);
if (error)
return error;
lease_clear_pending(fl, arg);
locks_wake_up_blocks(fl);
if (arg == F_UNLCK) {
struct file *filp = fl->fl_file;
f_delown(filp);
filp->f_owner.signum = 0;
fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
if (fl->fl_fasync != NULL) {
printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
fl->fl_fasync = NULL;
}
locks_delete_lock(before);
}
return 0;
}
EXPORT_SYMBOL(lease_modify);
static bool past_time(unsigned long then)
{
if (!then)
/* 0 is a special value meaning "this never expires": */
return false;
return time_after(jiffies, then);
}
static void time_out_leases(struct inode *inode)
{
struct file_lock **before;
struct file_lock *fl;
before = &inode->i_flock;
while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
if (past_time(fl->fl_downgrade_time))
lease_modify(before, F_RDLCK);
if (past_time(fl->fl_break_time))
lease_modify(before, F_UNLCK);
if (fl == *before) /* lease_modify may have freed fl */
before = &fl->fl_next;
}
}
static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
{
if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
return false;
return locks_conflict(breaker, lease);
}
/**
* __break_lease - revoke all outstanding leases on file
* @inode: the inode of the file to return
* @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
* break all leases
* @type: FL_LEASE: break leases and delegations; FL_DELEG: break
* only delegations
*
* break_lease (inlined for speed) has checked there already is at least
* some kind of lock (maybe a lease) on this file. Leases are broken on
* a call to open() or truncate(). This function can sleep unless you
* specified %O_NONBLOCK to your open().
*/
int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
{
int error = 0;
struct file_lock *new_fl, *flock;
struct file_lock *fl;
unsigned long break_time;
int i_have_this_lease = 0;
bool lease_conflict = false;
int want_write = (mode & O_ACCMODE) != O_RDONLY;
new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
if (IS_ERR(new_fl))
return PTR_ERR(new_fl);
new_fl->fl_flags = type;
spin_lock(&inode->i_lock);
time_out_leases(inode);
flock = inode->i_flock;
if ((flock == NULL) || !IS_LEASE(flock))
goto out;
for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
if (leases_conflict(fl, new_fl)) {
lease_conflict = true;
if (fl->fl_owner == current->files)
i_have_this_lease = 1;
}
}
if (!lease_conflict)
goto out;
break_time = 0;
if (lease_break_time > 0) {
break_time = jiffies + lease_break_time * HZ;
if (break_time == 0)
break_time++; /* so that 0 means no break time */
}
for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
if (!leases_conflict(fl, new_fl))
continue;
if (want_write) {
if (fl->fl_flags & FL_UNLOCK_PENDING)
continue;
fl->fl_flags |= FL_UNLOCK_PENDING;
fl->fl_break_time = break_time;
} else {
if (lease_breaking(flock))
continue;
fl->fl_flags |= FL_DOWNGRADE_PENDING;
fl->fl_downgrade_time = break_time;
}
fl->fl_lmops->lm_break(fl);
}
if (i_have_this_lease || (mode & O_NONBLOCK)) {
error = -EWOULDBLOCK;
goto out;
}
restart:
break_time = flock->fl_break_time;
if (break_time != 0) {
break_time -= jiffies;
if (break_time == 0)
break_time++;
}
locks_insert_block(flock, new_fl);
spin_unlock(&inode->i_lock);
error = wait_event_interruptible_timeout(new_fl->fl_wait,
!new_fl->fl_next, break_time);
spin_lock(&inode->i_lock);
locks_delete_block(new_fl);
if (error >= 0) {
if (error == 0)
time_out_leases(inode);
/*
* Wait for the next conflicting lease that has not been
* broken yet
*/
for (flock = inode->i_flock; flock && IS_LEASE(flock);
flock = flock->fl_next) {
if (leases_conflict(new_fl, flock))
goto restart;
}
error = 0;
}
out:
spin_unlock(&inode->i_lock);
locks_free_lock(new_fl);
return error;
}
EXPORT_SYMBOL(__break_lease);
/**
* lease_get_mtime - get the last modified time of an inode
* @inode: the inode
* @time: pointer to a timespec which will contain the last modified time
*
* This is to force NFS clients to flush their caches for files with
* exclusive leases. The justification is that if someone has an
* exclusive lease, then they could be modifying it.
*/
void lease_get_mtime(struct inode *inode, struct timespec *time)
{
struct file_lock *flock = inode->i_flock;
if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK))
*time = current_fs_time(inode->i_sb);
else
*time = inode->i_mtime;
}
EXPORT_SYMBOL(lease_get_mtime);
/**
* fcntl_getlease - Enquire what lease is currently active
* @filp: the file
*
* The value returned by this function will be one of
* (if no lease break is pending):
*
* %F_RDLCK to indicate a shared lease is held.
*
* %F_WRLCK to indicate an exclusive lease is held.
*
* %F_UNLCK to indicate no lease is held.
*
* (if a lease break is pending):
*
* %F_RDLCK to indicate an exclusive lease needs to be
* changed to a shared lease (or removed).
*
* %F_UNLCK to indicate the lease needs to be removed.
*
* XXX: sfr & willy disagree over whether F_INPROGRESS
* should be returned to userspace.
*/
int fcntl_getlease(struct file *filp)
{
struct file_lock *fl;
struct inode *inode = file_inode(filp);
int type = F_UNLCK;
spin_lock(&inode->i_lock);
time_out_leases(file_inode(filp));
for (fl = file_inode(filp)->i_flock; fl && IS_LEASE(fl);
fl = fl->fl_next) {
if (fl->fl_file == filp) {
type = target_leasetype(fl);
break;
}
}
spin_unlock(&inode->i_lock);
return type;
}
static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp)
{
struct file_lock *fl, **before, **my_before = NULL, *lease;
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
bool is_deleg = (*flp)->fl_flags & FL_DELEG;
int error;
lease = *flp;
/*
* In the delegation case we need mutual exclusion with
* a number of operations that take the i_mutex. We trylock
* because delegations are an optional optimization, and if
* there's some chance of a conflict--we'd rather not
* bother, maybe that's a sign this just isn't a good file to
* hand out a delegation on.
*/
if (is_deleg && !mutex_trylock(&inode->i_mutex))
return -EAGAIN;
if (is_deleg && arg == F_WRLCK) {
/* Write delegations are not currently supported: */
mutex_unlock(&inode->i_mutex);
WARN_ON_ONCE(1);
return -EINVAL;
}
error = -EAGAIN;
if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
goto out;
if ((arg == F_WRLCK)
&& ((d_count(dentry) > 1)
|| (atomic_read(&inode->i_count) > 1)))
goto out;
/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
* (otherwise our open of this file would have blocked).
* And if we are trying to acquire an exclusive lease,
* then the file is not open by anyone (including us)
* except for this filp.
*/
error = -EAGAIN;
for (before = &inode->i_flock;
((fl = *before) != NULL) && IS_LEASE(fl);
before = &fl->fl_next) {
if (fl->fl_file == filp) {
my_before = before;
continue;
}
/*
* No exclusive leases if someone else has a lease on
* this file:
*/
if (arg == F_WRLCK)
goto out;
/*
* Modifying our existing lease is OK, but no getting a
* new lease if someone else is opening for write:
*/
if (fl->fl_flags & FL_UNLOCK_PENDING)
goto out;
}
if (my_before != NULL) {
error = lease->fl_lmops->lm_change(my_before, arg);
if (!error)
*flp = *my_before;
goto out;
}
error = -EINVAL;
if (!leases_enable)
goto out;
locks_insert_lock(before, lease);
error = 0;
out:
if (is_deleg)
mutex_unlock(&inode->i_mutex);
return error;
}
static int generic_delete_lease(struct file *filp, struct file_lock **flp)
{
struct file_lock *fl, **before;
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
for (before = &inode->i_flock;
((fl = *before) != NULL) && IS_LEASE(fl);
before = &fl->fl_next) {
if (fl->fl_file != filp)
continue;
return (*flp)->fl_lmops->lm_change(before, F_UNLCK);
}
return -EAGAIN;
}
/**
* generic_setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @flp: input - file_lock to use, output - file_lock inserted
*
* The (input) flp->fl_lmops->lm_break function is required
* by break_lease().
*
* Called with inode->i_lock held.
*/
int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
{
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
int error;
if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
return -EACCES;
if (!S_ISREG(inode->i_mode))
return -EINVAL;
error = security_file_lock(filp, arg);
if (error)
return error;
time_out_leases(inode);
BUG_ON(!(*flp)->fl_lmops->lm_break);
switch (arg) {
case F_UNLCK:
return generic_delete_lease(filp, flp);
case F_RDLCK:
case F_WRLCK:
return generic_add_lease(filp, arg, flp);
default:
return -EINVAL;
}
}
EXPORT_SYMBOL(generic_setlease);
static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
{
if (filp->f_op->setlease)
return filp->f_op->setlease(filp, arg, lease);
else
return generic_setlease(filp, arg, lease);
}
/**
* vfs_setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @lease: file_lock to use
*
* Call this to establish a lease on the file.
* The (*lease)->fl_lmops->lm_break operation must be set; if not,
* break_lease will oops!
*
* This will call the filesystem's setlease file method, if
* defined. Note that there is no getlease method; instead, the
* filesystem setlease method should call back to setlease() to
* add a lease to the inode's lease list, where fcntl_getlease() can
* find it. Since fcntl_getlease() only reports whether the current
* task holds a lease, a cluster filesystem need only do this for
* leases held by processes on this node.
*
* There is also no break_lease method; filesystems that
* handle their own leases should break leases themselves from the
* filesystem's open, create, and (on truncate) setattr methods.
*
* Warning: the only current setlease methods exist only to disable
* leases in certain cases. More vfs changes may be required to
* allow a full filesystem lease implementation.
*/
int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
{
struct inode *inode = file_inode(filp);
int error;
spin_lock(&inode->i_lock);
error = __vfs_setlease(filp, arg, lease);
spin_unlock(&inode->i_lock);
return error;
}
EXPORT_SYMBOL_GPL(vfs_setlease);
static int do_fcntl_delete_lease(struct file *filp)
{
struct file_lock fl, *flp = &fl;
lease_init(filp, F_UNLCK, flp);
return vfs_setlease(filp, F_UNLCK, &flp);
}
static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock *fl, *ret;
struct inode *inode = file_inode(filp);
struct fasync_struct *new;
int error;
fl = lease_alloc(filp, arg);
if (IS_ERR(fl))
return PTR_ERR(fl);
new = fasync_alloc();
if (!new) {
locks_free_lock(fl);
return -ENOMEM;
}
ret = fl;
spin_lock(&inode->i_lock);
error = __vfs_setlease(filp, arg, &ret);
if (error) {
spin_unlock(&inode->i_lock);
locks_free_lock(fl);
goto out_free_fasync;
}
if (ret != fl)
locks_free_lock(fl);
/*
* fasync_insert_entry() returns the old entry if any.
* If there was no old entry, then it used 'new' and
* inserted it into the fasync list. Clear new so that
* we don't release it here.
*/
if (!fasync_insert_entry(fd, filp, &ret->fl_fasync, new))
new = NULL;
error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
spin_unlock(&inode->i_lock);
out_free_fasync:
if (new)
fasync_free(new);
return error;
}
/**
* fcntl_setlease - sets a lease on an open file
* @fd: open file descriptor
* @filp: file pointer
* @arg: type of lease to obtain
*
* Call this fcntl to establish a lease on the file.
* Note that you also need to call %F_SETSIG to
* receive a signal when the lease is broken.
*/
int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
if (arg == F_UNLCK)
return do_fcntl_delete_lease(filp);
return do_fcntl_add_lease(fd, filp, arg);
}
/**
* flock_lock_file_wait - Apply a FLOCK-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
*
* Add a FLOCK style lock to a file.
*/
int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
{
int error;
might_sleep();
for (;;) {
error = flock_lock_file(filp, fl);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
if (!error)
continue;
locks_delete_block(fl);
break;
}
return error;
}
EXPORT_SYMBOL(flock_lock_file_wait);
/**
* sys_flock: - flock() system call.
* @fd: the file descriptor to lock.
* @cmd: the type of lock to apply.
*
* Apply a %FL_FLOCK style lock to an open file descriptor.
* The @cmd can be one of
*
* %LOCK_SH -- a shared lock.
*
* %LOCK_EX -- an exclusive lock.
*
* %LOCK_UN -- remove an existing lock.
*
* %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
*
* %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
* processes read and write access respectively.
*/
SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
{
struct fd f = fdget(fd);
struct file_lock *lock;
int can_sleep, unlock;
int error;
error = -EBADF;
if (!f.file)
goto out;
can_sleep = !(cmd & LOCK_NB);
cmd &= ~LOCK_NB;
unlock = (cmd == LOCK_UN);
if (!unlock && !(cmd & LOCK_MAND) &&
!(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
goto out_putf;
error = flock_make_lock(f.file, &lock, cmd);
if (error)
goto out_putf;
if (can_sleep)
lock->fl_flags |= FL_SLEEP;
error = security_file_lock(f.file, lock->fl_type);
if (error)
goto out_free;
if (f.file->f_op->flock)
error = f.file->f_op->flock(f.file,
(can_sleep) ? F_SETLKW : F_SETLK,
lock);
else
error = flock_lock_file_wait(f.file, lock);
out_free:
locks_free_lock(lock);
out_putf:
fdput(f);
out:
return error;
}
/**
* vfs_test_lock - test file byte range lock
* @filp: The file to test lock for
* @fl: The lock to test; also used to hold result
*
* Returns -ERRNO on failure. Indicates presence of conflicting lock by
* setting conf->fl_type to something other than F_UNLCK.
*/
int vfs_test_lock(struct file *filp, struct file_lock *fl)
{
if (filp->f_op->lock)
return filp->f_op->lock(filp, F_GETLK, fl);
posix_test_lock(filp, fl);
return 0;
}
EXPORT_SYMBOL_GPL(vfs_test_lock);
static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
{
flock->l_pid = fl->fl_pid;
#if BITS_PER_LONG == 32
/*
* Make sure we can represent the posix lock via
* legacy 32bit flock.
*/
if (fl->fl_start > OFFT_OFFSET_MAX)
return -EOVERFLOW;
if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
return -EOVERFLOW;
#endif
flock->l_start = fl->fl_start;
flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock->l_whence = 0;
flock->l_type = fl->fl_type;
return 0;
}
#if BITS_PER_LONG == 32
static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
{
flock->l_pid = fl->fl_pid;
flock->l_start = fl->fl_start;
flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock->l_whence = 0;
flock->l_type = fl->fl_type;
}
#endif
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk(struct file *filp, struct flock __user *l)
{
struct file_lock file_lock;
struct flock flock;
int error;
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
error = -EINVAL;
if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
goto out;
error = flock_to_posix_lock(filp, &file_lock, &flock);
if (error)
goto out;
error = vfs_test_lock(filp, &file_lock);
if (error)
goto out;
flock.l_type = file_lock.fl_type;
if (file_lock.fl_type != F_UNLCK) {
error = posix_lock_to_flock(&flock, &file_lock);
if (error)
goto out;
}
error = -EFAULT;
if (!copy_to_user(l, &flock, sizeof(flock)))
error = 0;
out:
return error;
}
/**
* vfs_lock_file - file byte range lock
* @filp: The file to apply the lock to
* @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
* @fl: The lock to be applied
* @conf: Place to return a copy of the conflicting lock, if found.
*
* A caller that doesn't care about the conflicting lock may pass NULL
* as the final argument.
*
* If the filesystem defines a private ->lock() method, then @conf will
* be left unchanged; so a caller that cares should initialize it to
* some acceptable default.
*
* To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
* locks, the ->lock() interface may return asynchronously, before the lock has
* been granted or denied by the underlying filesystem, if (and only if)
* lm_grant is set. Callers expecting ->lock() to return asynchronously
* will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
* the request is for a blocking lock. When ->lock() does return asynchronously,
* it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
* request completes.
* If the request is for non-blocking lock the file system should return
* FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
* with the result. If the request timed out the callback routine will return a
* nonzero return code and the file system should release the lock. The file
* system is also responsible to keep a corresponding posix lock when it
* grants a lock so the VFS can find out which locks are locally held and do
* the correct lock cleanup when required.
* The underlying filesystem must not drop the kernel lock or call
* ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
* return code.
*/
int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
{
if (filp->f_op->lock)
return filp->f_op->lock(filp, cmd, fl);
else
return posix_lock_file(filp, fl, conf);
}
EXPORT_SYMBOL_GPL(vfs_lock_file);
static int do_lock_file_wait(struct file *filp, unsigned int cmd,
struct file_lock *fl)
{
int error;
error = security_file_lock(filp, fl->fl_type);
if (error)
return error;
for (;;) {
error = vfs_lock_file(filp, cmd, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
if (!error)
continue;
locks_delete_block(fl);
break;
}
return error;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
struct flock __user *l)
{
struct file_lock *file_lock = locks_alloc_lock();
struct flock flock;
struct inode *inode;
struct file *f;
int error;
if (file_lock == NULL)
return -ENOLCK;
/*
* This might block, so we do it before checking the inode.
*/
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
inode = file_inode(filp);
/* Don't allow mandatory locks on files that may be memory mapped
* and shared.
*/
if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
error = -EAGAIN;
goto out;
}
again:
error = flock_to_posix_lock(filp, file_lock, &flock);
if (error)
goto out;
if (cmd == F_SETLKW) {
file_lock->fl_flags |= FL_SLEEP;
}
error = -EBADF;
switch (flock.l_type) {
case F_RDLCK:
if (!(filp->f_mode & FMODE_READ))
goto out;
break;
case F_WRLCK:
if (!(filp->f_mode & FMODE_WRITE))
goto out;
break;
case F_UNLCK:
break;
default:
error = -EINVAL;
goto out;
}
error = do_lock_file_wait(filp, cmd, file_lock);
/*
* Attempt to detect a close/fcntl race and recover by
* releasing the lock that was just acquired.
*/
/*
* we need that spin_lock here - it prevents reordering between
* update of inode->i_flock and check for it done in close().
* rcu_read_lock() wouldn't do.
*/
spin_lock(¤t->files->file_lock);
f = fcheck(fd);
spin_unlock(¤t->files->file_lock);
if (!error && f != filp && flock.l_type != F_UNLCK) {
flock.l_type = F_UNLCK;
goto again;
}
out:
locks_free_lock(file_lock);
return error;
}
#if BITS_PER_LONG == 32
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
{
struct file_lock file_lock;
struct flock64 flock;
int error;
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
error = -EINVAL;
if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
goto out;
error = flock64_to_posix_lock(filp, &file_lock, &flock);
if (error)
goto out;
error = vfs_test_lock(filp, &file_lock);
if (error)
goto out;
flock.l_type = file_lock.fl_type;
if (file_lock.fl_type != F_UNLCK)
posix_lock_to_flock64(&flock, &file_lock);
error = -EFAULT;
if (!copy_to_user(l, &flock, sizeof(flock)))
error = 0;
out:
return error;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
struct flock64 __user *l)
{
struct file_lock *file_lock = locks_alloc_lock();
struct flock64 flock;
struct inode *inode;
struct file *f;
int error;
if (file_lock == NULL)
return -ENOLCK;
/*
* This might block, so we do it before checking the inode.
*/
error = -EFAULT;
if (copy_from_user(&flock, l, sizeof(flock)))
goto out;
inode = file_inode(filp);
/* Don't allow mandatory locks on files that may be memory mapped
* and shared.
*/
if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
error = -EAGAIN;
goto out;
}
again:
error = flock64_to_posix_lock(filp, file_lock, &flock);
if (error)
goto out;
if (cmd == F_SETLKW64) {
file_lock->fl_flags |= FL_SLEEP;
}
error = -EBADF;
switch (flock.l_type) {
case F_RDLCK:
if (!(filp->f_mode & FMODE_READ))
goto out;
break;
case F_WRLCK:
if (!(filp->f_mode & FMODE_WRITE))
goto out;
break;
case F_UNLCK:
break;
default:
error = -EINVAL;
goto out;
}
error = do_lock_file_wait(filp, cmd, file_lock);
/*
* Attempt to detect a close/fcntl race and recover by
* releasing the lock that was just acquired.
*/
spin_lock(¤t->files->file_lock);
f = fcheck(fd);
spin_unlock(¤t->files->file_lock);
if (!error && f != filp && flock.l_type != F_UNLCK) {
flock.l_type = F_UNLCK;
goto again;
}
out:
locks_free_lock(file_lock);
return error;
}
#endif /* BITS_PER_LONG == 32 */
/*
* This function is called when the file is being removed
* from the task's fd array. POSIX locks belonging to this task
* are deleted at this time.
*/
void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
struct file_lock lock;
/*
* If there are no locks held on this file, we don't need to call
* posix_lock_file(). Another process could be setting a lock on this
* file at the same time, but we wouldn't remove that lock anyway.
*/
if (!file_inode(filp)->i_flock)
return;
lock.fl_type = F_UNLCK;
lock.fl_flags = FL_POSIX | FL_CLOSE;
lock.fl_start = 0;
lock.fl_end = OFFSET_MAX;
lock.fl_owner = owner;
lock.fl_pid = current->tgid;
lock.fl_file = filp;
lock.fl_ops = NULL;
lock.fl_lmops = NULL;
vfs_lock_file(filp, F_SETLK, &lock, NULL);
if (lock.fl_ops && lock.fl_ops->fl_release_private)
lock.fl_ops->fl_release_private(&lock);
}
EXPORT_SYMBOL(locks_remove_posix);
/*
* This function is called on the last close of an open file.
*/
void locks_remove_flock(struct file *filp)
{
struct inode * inode = file_inode(filp);
struct file_lock *fl;
struct file_lock **before;
if (!inode->i_flock)
return;
if (filp->f_op->flock) {
struct file_lock fl = {
.fl_pid = current->tgid,
.fl_file = filp,
.fl_flags = FL_FLOCK,
.fl_type = F_UNLCK,
.fl_end = OFFSET_MAX,
};
filp->f_op->flock(filp, F_SETLKW, &fl);
if (fl.fl_ops && fl.fl_ops->fl_release_private)
fl.fl_ops->fl_release_private(&fl);
}
spin_lock(&inode->i_lock);
before = &inode->i_flock;
while ((fl = *before) != NULL) {
if (fl->fl_file == filp) {
if (IS_FLOCK(fl)) {
locks_delete_lock(before);
continue;
}
if (IS_LEASE(fl)) {
lease_modify(before, F_UNLCK);
continue;
}
/* What? */
BUG();
}
before = &fl->fl_next;
}
spin_unlock(&inode->i_lock);
}
/**
* posix_unblock_lock - stop waiting for a file lock
* @waiter: the lock which was waiting
*
* lockd needs to block waiting for locks.
*/
int
posix_unblock_lock(struct file_lock *waiter)
{
int status = 0;
spin_lock(&blocked_lock_lock);
if (waiter->fl_next)
__locks_delete_block(waiter);
else
status = -ENOENT;
spin_unlock(&blocked_lock_lock);
return status;
}
EXPORT_SYMBOL(posix_unblock_lock);
/**
* vfs_cancel_lock - file byte range unblock lock
* @filp: The file to apply the unblock to
* @fl: The lock to be unblocked
*
* Used by lock managers to cancel blocked requests
*/
int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
{
if (filp->f_op->lock)
return filp->f_op->lock(filp, F_CANCELLK, fl);
return 0;
}
EXPORT_SYMBOL_GPL(vfs_cancel_lock);
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
struct locks_iterator {
int li_cpu;
loff_t li_pos;
};
static void lock_get_status(struct seq_file *f, struct file_lock *fl,
loff_t id, char *pfx)
{
struct inode *inode = NULL;
unsigned int fl_pid;
if (fl->fl_nspid)
fl_pid = pid_vnr(fl->fl_nspid);
else
fl_pid = fl->fl_pid;
if (fl->fl_file != NULL)
inode = file_inode(fl->fl_file);
seq_printf(f, "%lld:%s ", id, pfx);
if (IS_POSIX(fl)) {
seq_printf(f, "%6s %s ",
(fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
(inode == NULL) ? "*NOINODE*" :
mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
} else if (IS_FLOCK(fl)) {
if (fl->fl_type & LOCK_MAND) {
seq_printf(f, "FLOCK MSNFS ");
} else {
seq_printf(f, "FLOCK ADVISORY ");
}
} else if (IS_LEASE(fl)) {
seq_printf(f, "LEASE ");
if (lease_breaking(fl))
seq_printf(f, "BREAKING ");
else if (fl->fl_file)
seq_printf(f, "ACTIVE ");
else
seq_printf(f, "BREAKER ");
} else {
seq_printf(f, "UNKNOWN UNKNOWN ");
}
if (fl->fl_type & LOCK_MAND) {
seq_printf(f, "%s ",
(fl->fl_type & LOCK_READ)
? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
: (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
} else {
seq_printf(f, "%s ",
(lease_breaking(fl))
? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
: (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
}
if (inode) {
#ifdef WE_CAN_BREAK_LSLK_NOW
seq_printf(f, "%d %s:%ld ", fl_pid,
inode->i_sb->s_id, inode->i_ino);
#else
/* userspace relies on this representation of dev_t ;-( */
seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
MAJOR(inode->i_sb->s_dev),
MINOR(inode->i_sb->s_dev), inode->i_ino);
#endif
} else {
seq_printf(f, "%d <none>:0 ", fl_pid);
}
if (IS_POSIX(fl)) {
if (fl->fl_end == OFFSET_MAX)
seq_printf(f, "%Ld EOF\n", fl->fl_start);
else
seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
} else {
seq_printf(f, "0 EOF\n");
}
}
static int locks_show(struct seq_file *f, void *v)
{
struct locks_iterator *iter = f->private;
struct file_lock *fl, *bfl;
fl = hlist_entry(v, struct file_lock, fl_link);
lock_get_status(f, fl, iter->li_pos, "");
list_for_each_entry(bfl, &fl->fl_block, fl_block)
lock_get_status(f, bfl, iter->li_pos, " ->");
return 0;
}
static void *locks_start(struct seq_file *f, loff_t *pos)
{
struct locks_iterator *iter = f->private;
iter->li_pos = *pos + 1;
lg_global_lock(&file_lock_lglock);
spin_lock(&blocked_lock_lock);
return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos);
}
static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
{
struct locks_iterator *iter = f->private;
++iter->li_pos;
return seq_hlist_next_percpu(v, &file_lock_list, &iter->li_cpu, pos);
}
static void locks_stop(struct seq_file *f, void *v)
{
spin_unlock(&blocked_lock_lock);
lg_global_unlock(&file_lock_lglock);
}
static const struct seq_operations locks_seq_operations = {
.start = locks_start,
.next = locks_next,
.stop = locks_stop,
.show = locks_show,
};
static int locks_open(struct inode *inode, struct file *filp)
{
return seq_open_private(filp, &locks_seq_operations,
sizeof(struct locks_iterator));
}
static const struct file_operations proc_locks_operations = {
.open = locks_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release_private,
};
static int __init proc_locks_init(void)
{
proc_create("locks", 0, NULL, &proc_locks_operations);
return 0;
}
module_init(proc_locks_init);
#endif
/**
* lock_may_read - checks that the region is free of locks
* @inode: the inode that is being read
* @start: the first byte to read
* @len: the number of bytes to read
*
* Emulates Windows locking requirements. Whole-file
* mandatory locks (share modes) can prohibit a read and
* byte-range POSIX locks can prohibit a read if they overlap.
*
* N.B. this function is only ever called
* from knfsd and ownership of locks is never checked.
*/
int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
{
struct file_lock *fl;
int result = 1;
spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if (fl->fl_type == F_RDLCK)
continue;
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
continue;
} else if (IS_FLOCK(fl)) {
if (!(fl->fl_type & LOCK_MAND))
continue;
if (fl->fl_type & LOCK_READ)
continue;
} else
continue;
result = 0;
break;
}
spin_unlock(&inode->i_lock);
return result;
}
EXPORT_SYMBOL(lock_may_read);
/**
* lock_may_write - checks that the region is free of locks
* @inode: the inode that is being written
* @start: the first byte to write
* @len: the number of bytes to write
*
* Emulates Windows locking requirements. Whole-file
* mandatory locks (share modes) can prohibit a write and
* byte-range POSIX locks can prohibit a write if they overlap.
*
* N.B. this function is only ever called
* from knfsd and ownership of locks is never checked.
*/
int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
{
struct file_lock *fl;
int result = 1;
spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
continue;
} else if (IS_FLOCK(fl)) {
if (!(fl->fl_type & LOCK_MAND))
continue;
if (fl->fl_type & LOCK_WRITE)
continue;
} else
continue;
result = 0;
break;
}
spin_unlock(&inode->i_lock);
return result;
}
EXPORT_SYMBOL(lock_may_write);
static int __init filelock_init(void)
{
int i;
filelock_cache = kmem_cache_create("file_lock_cache",
sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
lg_lock_init(&file_lock_lglock, "file_lock_lglock");
for_each_possible_cpu(i)
INIT_HLIST_HEAD(per_cpu_ptr(&file_lock_list, i));
return 0;
}
core_initcall(filelock_init);