ext4: call ext4_ioend_wait and ext4_flush_completed_IO in ext4_evict_inode

commit 2581fdc810889fdea97689cb62481201d579c796 upstream.

Flush inode's i_completed_io_list before calling ext4_io_wait to
prevent the following deadlock scenario: A page fault happens while
some process is writing inode A. 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.

Also moves ext4_flush_completed_IO and ext4_ioend_wait from
ext4_destroy_inode() to ext4_evict_inode(). During inode deleteion,
ext4_evict_inode() is called before ext4_destroy_inode() and in
ext4_evict_inode(), we may call ext4_truncate() without holding
i_mutex lock. As a result, there is a race between flush_completed_IO
that is called from ext4_ext_truncate() and ext4_end_io_work, which
may cause corruption on an io_end structure. This change moves
ext4_flush_completed_IO and ext4_ioend_wait from ext4_destroy_inode()
to ext4_evict_inode() to resolve the race between ext4_truncate() and
ext4_end_io_work during inode deletion.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 6 insertions, 1 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0b60a461e06..773de46d7f0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -189,6 +189,12 @@ void ext4_evict_inode(struct inode *inode)
         int err;
 
         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) {
                 truncate_inode_pages(&inode->i_data, 0);
                 goto no_delete;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9ea71aa864b..111ed9d3c54 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -892,7 +892,6 @@ static void ext4_i_callback(struct rcu_head *head)
 
 static void ext4_destroy_inode(struct inode *inode)
 {
-        ext4_ioend_wait(inode);
         if (!list_empty(&(EXT4_I(inode)->i_orphan))) {
                 ext4_msg(inode->i_sb, KERN_ERR,
                          "Inode %lu (%p): orphan list check failed!",