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authorAl Viro <viro@zeniv.linux.org.uk>2014-05-29 09:11:45 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-05-30 11:10:33 -0400
commitb2b80195d8829921506880f6dccd21cabd163d0d (patch)
tree4c0845c5bdbcfba145459fb1a5f9853f762fb64c
parent046b961b45f93a92e4c70525a12f3d378bced130 (diff)
downloadlinux-b2b80195d8829921506880f6dccd21cabd163d0d.tar.gz
dealing with the rest of shrink_dentry_list() livelock
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 <viro@zeniv.linux.org.uk>
-rw-r--r--fs/dcache.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index d54a99baf4f..eb7c7255470 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -885,8 +885,26 @@ 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;
+ }
}
}