mirror of
https://github.com/Divested-Mobile/DivestOS-Build.git
synced 2024-12-20 21:34:24 -05:00
78 lines
2.9 KiB
Diff
78 lines
2.9 KiB
Diff
From df6099279dc346ec77158d5f52d3176dbd0a1e4c Mon Sep 17 00:00:00 2001
|
|
From: Jan Kara <jack@suse.cz>
|
|
Date: Mon, 04 Jul 2016 10:14:01 -0400
|
|
Subject: [PATCH] ext4: fix deadlock during page writeback
|
|
|
|
[ Upstream commit 646caa9c8e196880b41cd3e3d33a2ebc752bdb85 ]
|
|
|
|
Commit 06bd3c36a733 (ext4: fix data exposure after a crash) uncovered a
|
|
deadlock in ext4_writepages() which was previously much harder to hit.
|
|
After this commit xfstest generic/130 reproduces the deadlock on small
|
|
filesystems.
|
|
|
|
The problem happens when ext4_do_update_inode() sets LARGE_FILE feature
|
|
and marks current inode handle as synchronous. That subsequently results
|
|
in ext4_journal_stop() called from ext4_writepages() to block waiting for
|
|
transaction commit while still holding page locks, reference to io_end,
|
|
and some prepared bio in mpd structure each of which can possibly block
|
|
transaction commit from completing and thus results in deadlock.
|
|
|
|
Fix the problem by releasing page locks, io_end reference, and
|
|
submitting prepared bio before calling ext4_journal_stop().
|
|
|
|
[ Changed to defer the call to ext4_journal_stop() only if the handle
|
|
is synchronous. --tytso ]
|
|
|
|
Change-Id: I724640d96ffaa03e512cd0b48cea056b4030c382
|
|
Reported-and-tested-by: Eryu Guan <eguan@redhat.com>
|
|
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
|
|
CC: stable@vger.kernel.org
|
|
Signed-off-by: Jan Kara <jack@suse.cz>
|
|
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
|
|
---
|
|
|
|
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
|
|
index f472aed..5aa499f 100644
|
|
--- a/fs/ext4/inode.c
|
|
+++ b/fs/ext4/inode.c
|
|
@@ -2554,13 +2554,36 @@
|
|
done = true;
|
|
}
|
|
}
|
|
- ext4_journal_stop(handle);
|
|
+ /*
|
|
+ * Caution: If the handle is synchronous,
|
|
+ * ext4_journal_stop() can wait for transaction commit
|
|
+ * to finish which may depend on writeback of pages to
|
|
+ * complete or on page lock to be released. In that
|
|
+ * case, we have to wait until after after we have
|
|
+ * submitted all the IO, released page locks we hold,
|
|
+ * and dropped io_end reference (for extent conversion
|
|
+ * to be able to complete) before stopping the handle.
|
|
+ */
|
|
+ if (!ext4_handle_valid(handle) || handle->h_sync == 0) {
|
|
+ ext4_journal_stop(handle);
|
|
+ handle = NULL;
|
|
+ }
|
|
/* Submit prepared bio */
|
|
ext4_io_submit(&mpd.io_submit);
|
|
/* Unlock pages we didn't use */
|
|
mpage_release_unused_pages(&mpd, give_up_on_write);
|
|
- /* Drop our io_end reference we got from init */
|
|
- ext4_put_io_end(mpd.io_submit.io_end);
|
|
+ /*
|
|
+ * Drop our io_end reference we got from init. We have
|
|
+ * to be careful and use deferred io_end finishing if
|
|
+ * we are still holding the transaction as we can
|
|
+ * release the last reference to io_end which may end
|
|
+ * up doing unwritten extent conversion.
|
|
+ */
|
|
+ if (handle) {
|
|
+ ext4_put_io_end_defer(mpd.io_submit.io_end);
|
|
+ ext4_journal_stop(handle);
|
|
+ } else
|
|
+ ext4_put_io_end(mpd.io_submit.io_end);
|
|
|
|
if (ret == -ENOSPC && sbi->s_journal) {
|
|
/*
|