Commit 6eac3f93 authored Oct 28, 2006 by Vasily Averin Committed by Linus Torvalds Oct 28, 2006

[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>

parent ebed4bfc

fs/dcache.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -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);
		}

Admin message