From: Al Viro <[email protected]> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== commit b2b80195d8829921506880f6dccd21cabd163d0d upstream. We have the same problem with ->d_lock order in the inner loop, where we are dropping references to ancestors. Same solution, basically - instead of using dentry_kill() we use lock_parent() (introduced in the previous commit) to get that lock in a safe way, recheck ->d_count (in case if lock_parent() has ended up dropping and retaking ->d_lock and somebody managed to grab a reference during that window), trylock the inode->i_lock and use __dentry_kill() to do the rest. Signed-off-by: Al Viro <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> --- fs/dcache.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index f37f7b5ad18c..e58a23f93495 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -907,8 +907,26 @@ static void shrink_dentry_list(struct list_head *list) * fragmentation. */ dentry = parent; - while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) - dentry = dentry_kill(dentry, 1); + while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) { + parent = lock_parent(dentry); + if (dentry->d_lockref.count != 1) { + dentry->d_lockref.count--; + spin_unlock(&dentry->d_lock); + if (parent) + spin_unlock(&parent->d_lock); + break; + } + inode = dentry->d_inode; /* can't be NULL */ + if (unlikely(!spin_trylock(&inode->i_lock))) { + spin_unlock(&dentry->d_lock); + if (parent) + spin_unlock(&parent->d_lock); + cpu_relax(); + continue; + } + __dentry_kill(dentry); + dentry = parent; + } } } -- 2.1.2 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
