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authorJiaying Zhang <jiayingz@google.com>2011-08-31 11:50:51 -0400
committerTheodore Ts'o <tytso@mit.edu>2011-08-31 11:50:51 -0400
commit8c0bec2151a47906bf779c6715a10ce04453ab77 (patch)
tree0165e80ba408b5db1e9e2adf9264bf4186b06768 /fs/ext4/inode.c
parentfcb8ce5cfe30ca9ca5c9a79cdfe26d1993e65e0c (diff)
ext4: remove i_mutex lock in ext4_evict_inode to fix lockdep complaining
The i_mutex lock and flush_completed_IO() added by commit 2581fdc810 in ext4_evict_inode() causes lockdep complaining about potential deadlock in several places. In most/all of these LOCKDEP complaints it looks like it's a false positive, since many of the potential circular locking cases can't take place by the time the ext4_evict_inode() is called; but since at the very least it may mask real problems, we need to address this. This change removes the flush_completed_IO() and i_mutex lock in ext4_evict_inode(). Instead, we take a different approach to resolve the software lockup that commit 2581fdc810 intends to fix. Rather than having ext4-dio-unwritten thread wait for grabing the i_mutex lock of an inode, we use mutex_trylock() instead, and simply requeue the work item if we fail to grab the inode's i_mutex lock. This should speed up work queue processing in general and also prevents the following deadlock scenario: During page fault, shrink_icache_memory is called that in turn evicts another inode B. Inode B has some pending io_end work so it calls ext4_ioend_wait() that waits for inode B's i_ioend_count to become zero. However, inode B's ioend work was queued behind some of inode A's ioend work on the same cpu's ext4-dio-unwritten workqueue. As the ext4-dio-unwritten thread on that cpu is processing inode A's ioend work, it tries to grab inode A's i_mutex lock. Since the i_mutex lock of inode A is still hold before the page fault happened, we enter a deadlock. Signed-off-by: Jiaying Zhang <jiayingz@google.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/inode.c')
-rw-r--r--fs/ext4/inode.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c4da98a959ae..18d2558b7624 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -121,9 +121,6 @@ void ext4_evict_inode(struct inode *inode)
trace_ext4_evict_inode(inode);
- mutex_lock(&inode->i_mutex);
- ext4_flush_completed_IO(inode);
- mutex_unlock(&inode->i_mutex);
ext4_ioend_wait(inode);
if (inode->i_nlink) {