[PATCH] missing unused dentry in prune_dcache()?

On the the following patch:
http://linux.bkbits.net:8080/linux-2.6/gnupatch@449b144ecSF1rYskg3q-SeR2vf88zg

# ChangeSet
#   2006/06/22 15:05:57-07:00 neilb@suse.de
#   [PATCH] Fix dcache race during umount

#   If prune_dcache finds a dentry that it cannot free, it leaves it where it
#   is (at the tail of the list) and exits, on the assumption that some other
#   thread will be removing that dentry soon.

However as far as I see this comment is not correct: when we cannot take
s_umount rw_semaphore (for example because it was taken in do_remount) this
dentry is already extracted from dentry_unused list and we do not add it
into the list again.  Therefore dentry will not be found by prune_dcache()
and shrink_dcache_sb() and will leave in memory very long time until the
partition will be unmounted.

The patch adds this dentry into tail of the dentry_unused list.

Signed-off-by: Vasily Averin <vvs@sw.ru>
Cc: Neil Brown <neilb@suse.de>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/dcache.c b/fs/dcache.c
index a1ff91e..a5b76b6 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -478,11 +478,12 @@ static void prune_dcache(int count, struct super_block *sb)
                        up_read(s_umount);
                }
                spin_unlock(&dentry->d_lock);
-               /* Cannot remove the first dentry, and it isn't appropriate
-                * to move it to the head of the list, so give up, and try
-                * later
+               /*
+                * Insert dentry at the head of the list as inserting at the
+                * tail leads to a cycle.
                 */
-               break;
+               list_add(&dentry->d_lru, &dentry_unused);
+               dentry_stat.nr_unused++;
        }
        spin_unlock(&dcache_lock);
 }