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authorAl Viro <viro@www.linux.org.uk>2005-06-06 16:36:05 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-06 17:42:25 -0400
commit463ffb2e9d39c2a3fd8c3c1d4a34e01f2078f972 (patch)
treee5d9b39aca2a546bf2b832c5a2a7066e34f9c1b5
parentd671d5e51400aab03c713a16ce3545aa81ad7b1c (diff)
[PATCH] namei fixes (9/19)
New helper: __follow_mount(struct path *path). Same as follow_mount(), except that we do *not* do mntput() after the first lookup_mnt(). IOW, original path->mnt stays pinned down. We also take care to do dput() before mntput() in the loop body (follow_mount() also needs that reordering, but that will be done later in the series). The following are equivalent, assuming that path.mnt == x: (1) follow_mount(&path.mnt, &path.dentry) (2) __follow_mount(&path); if (path->mnt != x) mntput(x); (3) if (__follow_mount(&path)) mntput(x); Callers of follow_mount() in __link_path_walk() converted to (2). Equivalent transformation + fix for too-late-mntput() race in __follow_mount() loop. Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--fs/namei.c25
1 files changed, 23 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 3d08478d3130..23a1ad467976 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -576,6 +576,23 @@ int follow_up(struct vfsmount **mnt, struct dentry **dentry)
576/* no need for dcache_lock, as serialization is taken care in 576/* no need for dcache_lock, as serialization is taken care in
577 * namespace.c 577 * namespace.c
578 */ 578 */
579static int __follow_mount(struct path *path)
580{
581 int res = 0;
582 while (d_mountpoint(path->dentry)) {
583 struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry);
584 if (!mounted)
585 break;
586 dput(path->dentry);
587 if (res)
588 mntput(path->mnt);
589 path->mnt = mounted;
590 path->dentry = dget(mounted->mnt_root);
591 res = 1;
592 }
593 return res;
594}
595
579static int follow_mount(struct vfsmount **mnt, struct dentry **dentry) 596static int follow_mount(struct vfsmount **mnt, struct dentry **dentry)
580{ 597{
581 int res = 0; 598 int res = 0;
@@ -778,7 +795,9 @@ static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
778 if (err) 795 if (err)
779 break; 796 break;
780 /* Check mountpoints.. */ 797 /* Check mountpoints.. */
781 follow_mount(&next.mnt, &next.dentry); 798 __follow_mount(&next);
799 if (nd->mnt != next.mnt)
800 mntput(nd->mnt);
782 801
783 err = -ENOENT; 802 err = -ENOENT;
784 inode = next.dentry->d_inode; 803 inode = next.dentry->d_inode;
@@ -836,7 +855,9 @@ last_component:
836 err = do_lookup(nd, &this, &next); 855 err = do_lookup(nd, &this, &next);
837 if (err) 856 if (err)
838 break; 857 break;
839 follow_mount(&next.mnt, &next.dentry); 858 __follow_mount(&next);
859 if (nd->mnt != next.mnt)
860 mntput(nd->mnt);
840 inode = next.dentry->d_inode; 861 inode = next.dentry->d_inode;
841 if ((lookup_flags & LOOKUP_FOLLOW) 862 if ((lookup_flags & LOOKUP_FOLLOW)
842 && inode && inode->i_op && inode->i_op->follow_link) { 863 && inode && inode->i_op && inode->i_op->follow_link) {