/
locks.c
2236 lines (2000 loc) · 55.2 KB
/
locks.c
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/*
* 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/mandatory.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/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/rcupdate.h>
#include <asm/semaphore.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)
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)
static LIST_HEAD(file_lock_list);
static LIST_HEAD(blocked_list);
static struct kmem_cache *filelock_cache __read_mostly;
/* Allocate an empty lock structure. */
static struct file_lock *locks_alloc_lock(void)
{
return kmem_cache_alloc(filelock_cache, GFP_KERNEL);
}
static 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;
}
if (fl->fl_lmops) {
if (fl->fl_lmops->fl_release_private)
fl->fl_lmops->fl_release_private(fl);
fl->fl_lmops = NULL;
}
}
/* Free a lock which is not in use. */
static void locks_free_lock(struct file_lock *fl)
{
BUG_ON(waitqueue_active(&fl->fl_wait));
BUG_ON(!list_empty(&fl->fl_block));
BUG_ON(!list_empty(&fl->fl_link));
locks_release_private(fl);
kmem_cache_free(filelock_cache, fl);
}
void locks_init_lock(struct file_lock *fl)
{
INIT_LIST_HEAD(&fl->fl_link);
INIT_LIST_HEAD(&fl->fl_block);
init_waitqueue_head(&fl->fl_wait);
fl->fl_next = NULL;
fl->fl_fasync = NULL;
fl->fl_owner = NULL;
fl->fl_pid = 0;
fl->fl_file = NULL;
fl->fl_flags = 0;
fl->fl_type = 0;
fl->fl_start = fl->fl_end = 0;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
}
EXPORT_SYMBOL(locks_init_lock);
/*
* Initialises the fields of the file lock which are invariant for
* free file_locks.
*/
static void init_once(void *foo, struct kmem_cache *cache, unsigned long flags)
{
struct file_lock *lock = (struct file_lock *) foo;
if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
SLAB_CTOR_CONSTRUCTOR)
return;
locks_init_lock(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) {
if (fl->fl_lmops->fl_copy_lock)
fl->fl_lmops->fl_copy_lock(new, fl);
new->fl_lmops = fl->fl_lmops;
}
}
/*
* Initialize a new lock from an existing file_lock structure.
*/
static 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;
}
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, int 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(filp->f_path.dentry->d_inode);
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(filp->f_path.dentry->d_inode);
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;
switch (l->l_type) {
case F_RDLCK:
case F_WRLCK:
case F_UNLCK:
fl->fl_type = l->l_type;
break;
default:
return -EINVAL;
}
return (0);
}
#endif
/* default lease lock manager operations */
static void lease_break_callback(struct file_lock *fl)
{
kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
}
static void lease_release_private_callback(struct file_lock *fl)
{
if (!fl->fl_file)
return;
f_delown(fl->fl_file);
fl->fl_file->f_owner.signum = 0;
}
static int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
{
return fl->fl_file == try->fl_file;
}
static struct lock_manager_operations lease_manager_ops = {
.fl_break = lease_break_callback,
.fl_release_private = lease_release_private_callback,
.fl_mylease = lease_mylease_callback,
.fl_change = lease_modify,
};
/*
* Initialize a lease, use the default lock manager operations
*/
static int lease_init(struct file *filp, int 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 int lease_alloc(struct file *filp, int type, struct file_lock **flp)
{
struct file_lock *fl = locks_alloc_lock();
int error = -ENOMEM;
if (fl == NULL)
goto out;
error = lease_init(filp, type, fl);
if (error) {
locks_free_lock(fl);
fl = NULL;
}
out:
*flp = fl;
return error;
}
/* 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->fl_compare_owner)
return fl2->fl_lmops == fl1->fl_lmops &&
fl1->fl_lmops->fl_compare_owner(fl1, fl2);
return fl1->fl_owner == fl2->fl_owner;
}
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
*/
static void __locks_delete_block(struct file_lock *waiter)
{
list_del_init(&waiter->fl_block);
list_del_init(&waiter->fl_link);
waiter->fl_next = NULL;
}
/*
*/
static void locks_delete_block(struct file_lock *waiter)
{
lock_kernel();
__locks_delete_block(waiter);
unlock_kernel();
}
/* 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.
*/
static void locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
BUG_ON(!list_empty(&waiter->fl_block));
list_add_tail(&waiter->fl_block, &blocker->fl_block);
waiter->fl_next = blocker;
if (IS_POSIX(blocker))
list_add(&waiter->fl_link, &blocked_list);
}
/* Wake up processes blocked waiting for blocker.
* If told to wait then schedule the processes until the block list
* is empty, otherwise empty the block list ourselves.
*/
static void locks_wake_up_blocks(struct file_lock *blocker)
{
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter = list_entry(blocker->fl_block.next,
struct file_lock, fl_block);
__locks_delete_block(waiter);
if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
waiter->fl_lmops->fl_notify(waiter);
else
wake_up(&waiter->fl_wait);
}
}
/* 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.
*/
static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
{
list_add(&fl->fl_link, &file_lock_list);
/* insert into file's list */
fl->fl_next = *pos;
*pos = fl;
if (fl->fl_ops && fl->fl_ops->fl_insert)
fl->fl_ops->fl_insert(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.
*/
static void locks_delete_lock(struct file_lock **thisfl_p)
{
struct file_lock *fl = *thisfl_p;
*thisfl_p = fl->fl_next;
fl->fl_next = NULL;
list_del_init(&fl->fl_link);
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;
}
if (fl->fl_ops && fl->fl_ops->fl_remove)
fl->fl_ops->fl_remove(fl);
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));
}
static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
{
int result = 0;
DECLARE_WAITQUEUE(wait, current);
__set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(fl_wait, &wait);
if (timeout == 0)
schedule();
else
result = schedule_timeout(timeout);
if (signal_pending(current))
result = -ERESTARTSYS;
remove_wait_queue(fl_wait, &wait);
__set_current_state(TASK_RUNNING);
return result;
}
static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
{
int result;
locks_insert_block(blocker, waiter);
result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
__locks_delete_block(waiter);
return result;
}
int
posix_test_lock(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
struct file_lock *cfl;
lock_kernel();
for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
continue;
if (posix_locks_conflict(cfl, fl))
break;
}
if (cfl) {
__locks_copy_lock(conflock, cfl);
unlock_kernel();
return 1;
}
unlock_kernel();
return 0;
}
EXPORT_SYMBOL(posix_test_lock);
/* This function tests for deadlock condition before putting a process to
* sleep. The detection scheme is no longer recursive. Recursive was neat,
* but dangerous - we risked stack corruption if the lock data was bad, or
* if the recursion was too deep for any other reason.
*
* We rely on the fact that a task can only be on one lock's wait queue
* at a time. When we find blocked_task on a wait queue we can re-search
* with blocked_task equal to that queue's owner, until either blocked_task
* isn't found, or blocked_task is found on a queue owned by my_task.
*
* Note: the above assumption may not be true when handling lock requests
* from a broken NFS client. But broken NFS clients have a lot more to
* worry about than proper deadlock detection anyway... --okir
*/
static int posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
struct list_head *tmp;
next_task:
if (posix_same_owner(caller_fl, block_fl))
return 1;
list_for_each(tmp, &blocked_list) {
struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
if (posix_same_owner(fl, block_fl)) {
fl = fl->fl_next;
block_fl = fl;
goto next_task;
}
}
return 0;
}
/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
* at the head of the list, but that's secret knowledge known only to
* flock_lock_file and posix_lock_file.
*
* 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 = filp->f_path.dentry->d_inode;
int error = 0;
int found = 0;
lock_kernel();
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;
}
error = -ENOMEM;
new_fl = locks_alloc_lock();
if (new_fl == NULL)
goto out;
/*
* If a higher-priority process was blocked on the old file lock,
* give it the opportunity to lock the file.
*/
if (found)
cond_resched();
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)
locks_insert_block(fl, request);
goto out;
}
if (request->fl_flags & FL_ACCESS)
goto out;
locks_copy_lock(new_fl, request);
locks_insert_lock(&inode->i_flock, new_fl);
new_fl = NULL;
error = 0;
out:
unlock_kernel();
if (new_fl)
locks_free_lock(new_fl);
return error;
}
static int __posix_lock_file_conf(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, added = 0;
/*
* 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();
}
lock_kernel();
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
struct file_lock *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;
error = -EDEADLK;
if (posix_locks_deadlock(request, fl))
goto out;
error = -EAGAIN;
locks_insert_block(fl, request);
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 = 1;
}
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 = 1;
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 = 1;
}
}
/* 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 bellow 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:
unlock_kernel();
/*
* Free any unused locks.
*/
if (new_fl)
locks_free_lock(new_fl);