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[GFS2] Fix recursive locking in gfs2_permission 

Since gfs2_permission may be called either from the VFS (in which case
we need to obtain a shared glock) or from GFS2 (in which case we already
have a glock) we need to test to see whether or not a lock is required.
The original test was buggy due to a potential race. This one should
be safe.

This fixes Red Hat bugzilla #217129

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Steven Whitehouse 2006-11-27 09:55:28 -05:00
parent cb4c031318
commit 300c7d75f3
1 changed files with 14 additions and 7 deletions
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21
fs/gfs2/ops_inode.c
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@ -835,6 +835,10 @@ static void *gfs2_follow_link(struct dentry *dentry, struct nameidata *nd)
* @mask:
* @nd: passed from Linux VFS, ignored by us
*
* This may be called from the VFS directly, or from within GFS2 with the
* inode locked, so we look to see if the glock is already locked and only
* lock the glock if its not already been done.
*
* Returns: errno
*/
@ -843,16 +847,19 @@ static int gfs2_permission(struct inode *inode, int mask, struct nameidata *nd)
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_holder i_gh;
int error;
int unlock = 0;
if (!test_bit(GIF_INVALID, &ip->i_flags))
return generic_permission(inode, mask, gfs2_check_acl);
error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
if (!error) {
error = generic_permission(inode, mask, gfs2_check_acl_locked);
gfs2_glock_dq_uninit(&i_gh);
if (gfs2_glock_is_locked_by_me(ip->i_gl) == 0) {
error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
if (error)
return error;
unlock = 1;
}
error = generic_permission(inode, mask, gfs2_check_acl_locked);
if (unlock)
gfs2_glock_dq_uninit(&i_gh);
return error;
}