From: Gao Xiang <[email protected]>
commit 41663430588c737dd735bad5a0d1ba325dcabd59 upstream.
SWP_FS is used to make swap_{read,write}page() go through the
filesystem, and it's only used for swap files over NFS. So, !SWP_FS
means non NFS for now, it could be either file backed or device backed.
Something similar goes with legacy SWP_FILE.
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 reproducible 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
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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
Reviewed-by: Yang Shi <[email protected]>
Acked-by: Rafael Aquini <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Carlos Maiolino <[email protected]>
Cc: Eric Sandeen <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/swapfile.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -973,7 +973,7 @@ start_over:
goto nextsi;
}
if (cluster) {
- if (!(si->flags & SWP_FILE))
+ if (si->flags & SWP_BLKDEV)
n_ret = swap_alloc_cluster(si, swp_entries);
} else
n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
