The patch titled
Subject: mm, THP, swap: fix allocating cluster for swapfile by mistake
has been added to the -mm tree. Its filename is
mm-thp-swap-fix-allocating-cluster-for-swapfile-by-mistake.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-thp-swap-fix-allocating-cluster-for-swapfile-by-mistake.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-swap-fix-allocating-cluster-for-swapfile-by-mistake.patch
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From: Gao Xiang <hsiangkao@xxxxxxxxxx>
Subject: mm, THP, swap: fix allocating cluster for swapfile by mistake
SWP_FS doesn't mean the device is file-backed swap device, which just
means each writeback request should go through fs by DIO. Or it'll just
use extents added by .swap_activate(), but it also works as file-backed
swap device.
So in order to achieve the goal of the original patch, SWP_BLKDEV should
be used instead.
FS corruption can be observed with SSD device + XFS + fragmented swapfile
due to CONFIG_THP_SWAP=y.
I reproduced the issue with the following details:
Environment:
QEMU + upstream kernel + buildroot + NVMe (2 GB)
Kernel config:
CONFIG_BLK_DEV_NVME=y
CONFIG_THP_SWAP=y
Some reproducable steps:
mkfs.xfs -f /dev/nvme0n1
mkdir /tmp/mnt
mount /dev/nvme0n1 /tmp/mnt
bs="32k"
sz="1024m" # doesn't matter too much, I also tried 16m
xfs_io -f -c "pwrite -R -b $bs 0 $sz" -c "fdatasync" /tmp/mnt/sw
xfs_io -f -c "pwrite -R -b $bs 0 $sz" -c "fdatasync" /tmp/mnt/sw
xfs_io -f -c "pwrite -R -b $bs 0 $sz" -c "fdatasync" /tmp/mnt/sw
xfs_io -f -c "pwrite -F -S 0 -b $bs 0 $sz" -c "fdatasync" /tmp/mnt/sw
xfs_io -f -c "pwrite -R -b $bs 0 $sz" -c "fsync" /tmp/mnt/sw
mkswap /tmp/mnt/sw
swapon /tmp/mnt/sw
stress --vm 2 --vm-bytes 600M # doesn't matter too much as well
Symptoms:
- FS corruption (e.g. checksum failure)
- memory corruption at: 0xd2808010
- segfault
Link: https://lkml.kernel.org/r/20200819195613.24269-1-hsiangkao@xxxxxxxxxx
Fixes: f0eea189e8e9 ("mm, THP, swap: Don't allocate huge cluster for file backed swap device")
Fixes: 38d8b4e6bdc8 ("mm, THP, swap: delay splitting THP during swap out")
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/swapfile.c~mm-thp-swap-fix-allocating-cluster-for-swapfile-by-mistake
+++ a/mm/swapfile.c
@@ -1078,7 +1078,7 @@ start_over:
goto nextsi;
}
if (size == SWAPFILE_CLUSTER) {
- if (!(si->flags & SWP_FS))
+ if (si->flags & SWP_BLKDEV)
n_ret = swap_alloc_cluster(si, swp_entries);
} else
n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
_
Patches currently in -mm which might be from hsiangkao@xxxxxxxxxx are
mm-thp-swap-fix-allocating-cluster-for-swapfile-by-mistake.patch
