Messages in this thread Patch in this message | | | Date | Fri, 27 Oct 2006 10:32:35 +0400 | From | Vasily Averin <> | Subject | Re: [Q] missing unused dentry in prune_dcache()? |
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David Howells wrote: > Vasily Averin <vvs@sw.ru> wrote: > >> I've noticed one more minor issue in your patch: in >> shrink_dcache_for_umount_subtree() function you decrement >> dentry_stat.nr_dentry without dcache_lock. > > How about the attached patch? I'm sorry, but your patch is wrong: you have mixed calculation of 2 variables: dentry_stat.nr_unused -- were correct, it was decremented under dcache_lock. dentry_stat.nr_dentry -- were incorrect, it was decremented without dcache_lock.
You should correct dentry_stat.nr_dentry, but instead you broke calculation of dentry_stat.nr_unused.
I've fixed this issue by following patch.
Thank you, Vasily Averin --- VFS: Fix an error in dentry_stat.nr_dentry counting
From: Vasily Averin <vvs@sw.ru>
Fix an error in dentry_stat.nr_dentry counting in shrink_dcache_for_umount_subtree() in which the count is modified without the dcache_lock held.
Signed-Off-By: Vasily Averin <vvs@sw.ru>
--- linux-2.6.19-rc3/fs/dcache.c.nrdntr 2006-10-26 15:14:51.000000000 +0400 +++ linux-2.6.19-rc3/fs/dcache.c 2006-10-27 10:24:07.000000000 +0400 @@ -554,6 +554,7 @@ repeat: static void shrink_dcache_for_umount_subtree(struct dentry *dentry) { struct dentry *parent; + unsigned detached = 0;
BUG_ON(!IS_ROOT(dentry));
@@ -618,7 +619,7 @@ static void shrink_dcache_for_umount_sub atomic_dec(&parent->d_count);
list_del(&dentry->d_u.d_child); - dentry_stat.nr_dentry--; /* For d_free, below */ + detached++;
inode = dentry->d_inode; if (inode) { @@ -635,8 +636,8 @@ static void shrink_dcache_for_umount_sub /* finished when we fall off the top of the tree, * otherwise we ascend to the parent and move to the * next sibling if there is one */ - if (!parent) - return; + if (!parent) + goto out;
dentry = parent;
@@ -645,6 +646,11 @@ static void shrink_dcache_for_umount_sub dentry = list_entry(dentry->d_subdirs.next, struct dentry, d_u.d_child); } +out: + /* several dentries were freed, need to correct nr_dentry */ + spin_lock(&dcache_lock); + dentry_stat.nr_dentry -= detached; + spin_unlock(&dcache_lock); }
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