Commit 5842add2 authored by Andy Adamson's avatar Andy Adamson Committed by Linus Torvalds
Browse files

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



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: default avatarAndy Adamson <andros@citi.umich.edu>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6dc0fe8f

fs/locks.c

+24 −8
Original line number Diff line number Diff line
@@ -792,9 +792,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *new_fl) 
	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 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, 
		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 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, 
		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,

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *);