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xfs: xfs_reflink_convert_cow() memory allocation deadlock

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xfs_reflink_convert_cow() manipulates the incore extent list
in GFP_KERNEL context in the IO submission path whilst holding
locked pages under writeback. This is a memory reclaim deadlock
vector. This code is not in a transaction, so any memory allocations
it makes aren't protected via the memalloc_nofs_save() context that
transactions carry.

Hence we need to run this call under memalloc_nofs_save() context to
prevent potential memory allocations from being run as GFP_KERNEL
and deadlocking.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Dave Chinner
2018-06-07 07:46:42 -07:00
committed by Darrick J. Wong
parent ef215e394e
commit 4a2d01b076
3 changed files with 12 additions and 1 deletions
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fs/xfs/xfs_linux.h
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@@ -26,6 +26,7 @@ typedef __u32 xfs_nlink_t;
#include <linux/semaphore.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/slab.h>