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[PATCH] VFS,fs/locks.c,NFSD4: add race_free posix_lock_file_conf() interface

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Lockd and the NFSv4 server both exercise a race condition where
posix_test_lock() is called either before or after posix_lock_file() to
deal with a denied lock request due to a conflicting lock.

Remove the race condition for the NFSv4 server by adding a new conflicting
lock parameter to __posix_lock_file() , changing the name to
__posix_lock_file_conf().

Keep posix_lock_file() interface, add posix_lock_conf() interface, both
call __posix_lock_file_conf().

[akpm@osdl.org: Put the EXPORT_SYMBOL() where it belongs]
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andy Adamson 2006-03-26 01:37:26 -08:00 committed by Linus Torvalds
parent 6dc0fe8f8b
commit 5842add2f3
2 changed files with 25 additions and 8 deletions
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32
fs/locks.c
View file

@ -792,9 +792,7 @@ out:
return error;
}
EXPORT_SYMBOL(posix_lock_file);
static int __posix_lock_file(struct inode *inode, struct file_lock *request)
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, *new_fl2;
@ -818,6 +816,8 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request)
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;
@ -987,8 +987,24 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request)
*/
int posix_lock_file(struct file *filp, struct file_lock *fl)
{
return __posix_lock_file(filp->f_dentry->d_inode, fl);
return __posix_lock_file_conf(filp->f_dentry->d_inode, fl, NULL);
}
EXPORT_SYMBOL(posix_lock_file);
/**
* posix_lock_file_conf - 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.
*
* Except for the conflock parameter, acts just like posix_lock_file.
*/
int posix_lock_file_conf(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
return __posix_lock_file_conf(filp->f_dentry->d_inode, fl, conflock);
}
EXPORT_SYMBOL(posix_lock_file_conf);
/**
* posix_lock_file_wait - Apply a POSIX-style lock to a file
@ -1004,7 +1020,7 @@ int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
int error;
might_sleep ();
for (;;) {
error = __posix_lock_file(filp->f_dentry->d_inode, fl);
error = posix_lock_file(filp, fl);
if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
break;
error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
@ -1076,7 +1092,7 @@ int locks_mandatory_area(int read_write, struct inode *inode,
fl.fl_end = offset + count - 1;
for (;;) {
error = __posix_lock_file(inode, &fl);
error = __posix_lock_file_conf(inode, &fl, NULL);
if (error != -EAGAIN)
break;
if (!(fl.fl_flags & FL_SLEEP))
@ -1689,7 +1705,7 @@ again:
error = filp->f_op->lock(filp, cmd, file_lock);
else {
for (;;) {
error = __posix_lock_file(inode, file_lock);
error = posix_lock_file(filp, file_lock);
if ((error != -EAGAIN) || (cmd == F_SETLK))
break;
error = wait_event_interruptible(file_lock->fl_wait,
@ -1832,7 +1848,7 @@ again:
error = filp->f_op->lock(filp, cmd, file_lock);
else {
for (;;) {
error = __posix_lock_file(inode, file_lock);
error = posix_lock_file(filp, file_lock);
if ((error != -EAGAIN) || (cmd == F_SETLK64))
break;
error = wait_event_interruptible(file_lock->fl_wait,

1
include/linux/fs.h
View file

@ -763,6 +763,7 @@ extern void locks_copy_lock(struct file_lock *, struct file_lock *);
extern void locks_remove_posix(struct file *, fl_owner_t);
extern void locks_remove_flock(struct file *);
extern int posix_test_lock(struct file *, struct file_lock *, struct file_lock *);
extern int posix_lock_file_conf(struct file *, struct file_lock *, struct file_lock *);
extern int posix_lock_file(struct file *, struct file_lock *);
extern int posix_lock_file_wait(struct file *, struct file_lock *);
extern int posix_unblock_lock(struct file *, struct file_lock *);