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Subject[PATCH 1/2] ext4: do not left pages locked in mpage_da_submit_io()
Date
If call to ext4_init_io_end() is failed under memory pressure,
mpage_da_submit_io() just returns -ENOMEM and left all pages
from the extent locked. That leads to a deadlock as soon as
callers of mpage_da_submit_io() expect it unlocks all the pages.

Found by Linux File System Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
fs/ext4/inode.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 793d44b..aeca439 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1489,8 +1489,9 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
BUG_ON(mpd->next_page <= mpd->first_page);
ext4_io_submit_init(&io_submit, mpd->wbc);
io_submit.io_end = ext4_init_io_end(inode, GFP_NOFS);
+ /* In case of error we still have to unlock pages */
if (!io_submit.io_end)
- return -ENOMEM;
+ ret = -ENOMEM;
/*
* We need to start from the first_page to the next_page - 1
* to make sure we also write the mapped dirty buffer_heads.
@@ -1512,6 +1513,11 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
index = page->index;
if (index > end)
break;
+ if (!io_submit.io_end) {
+ unlock_page(page);
+ index++;
+ continue;
+ }

if (index == size >> PAGE_CACHE_SHIFT)
len = size & ~PAGE_CACHE_MASK;
@@ -1577,9 +1583,11 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
}
pagevec_release(&pvec);
}
- ext4_io_submit(&io_submit);
- /* Drop io_end reference we got from init */
- ext4_put_io_end_defer(io_submit.io_end);
+ if (io_submit.io_end) {
+ ext4_io_submit(&io_submit);
+ /* Drop io_end reference we got from init */
+ ext4_put_io_end_defer(io_submit.io_end);
+ }
return ret;
}

--
1.7.9.5


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