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@xxxxxxxxxx>
---
fs/ext4/inode.c | 6 ++++++
fs/ext4/super.c | 1 -
2 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index de50b16..2aba49e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -120,6 +120,12 @@ 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 9ea71aa..111ed9d 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!",
--
1.7.3.1
--
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