[PATCH] locks: fix F_GETLK regression (failure to find conflicts)

From: J. Bruce Fields
Date: Thu May 10 2007 - 18:38:56 EST


In 9d6a8c5c213e34c475e72b245a8eb709258e968c we changed posix_test_lock
to modify its single file_lock argument instead of taking separate input
and output arguments. This makes it no longer safe to set the output
lock's fl_type to F_UNLCK before looking for a conflict, since that
means searching for a conflict against a lock with type F_UNLCK.

This fixes a regression which causes F_GETLK to incorrectly report no
conflict on most filesystems (including any filesystem that doesn't do
its own locking).

Also fix posix_lock_to_flock() to copy the lock type. This isn't
strictly necessary, since the caller already does this; but it seems
less likely to cause confusion in the future.

Thanks to Doug Chapman for the bug report.

Signed-off-by: "J. Bruce Fields" <bfields@xxxxxxxxxxxxxx>
---
fs/locks.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 671a034..8ec16ab 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -669,7 +669,6 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
{
struct file_lock *cfl;

- fl->fl_type = F_UNLCK;
lock_kernel();
for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
@@ -681,7 +680,8 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
__locks_copy_lock(fl, cfl);
unlock_kernel();
return 1;
- }
+ } else
+ fl->fl_type = F_UNLCK;
unlock_kernel();
return 0;
}
@@ -1632,6 +1632,7 @@ static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
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;
}

--
1.5.1.1.107.g7a159

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/