Subject: [merged] swap-fix-set_blocksize-race-during-swapon-swapoff.patch removed from -mm tree
To: k.kozlowski@xxxxxxxxxxx,bob.liu@xxxxxxxxxx,hughd@xxxxxxxxxx,konrad.wilk@xxxxxxxxxx,minchan@xxxxxxxxxx,shli@xxxxxxxxxxxx,weijie.yang.kh@xxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 17 Oct 2013 11:13:29 -0700
The patch titled
Subject: swap: fix set_blocksize race during swapon/swapoff
has been removed from the -mm tree. Its filename was
swap-fix-set_blocksize-race-during-swapon-swapoff.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Subject: swap: fix set_blocksize race during swapon/swapoff
Fix race between swapoff and swapon. Swapoff used old_block_size from
swap_info outside of swapon_mutex so it could be overwritten by concurrent
swapon.
The race has visible effect only if more than one swap block device exists
with different block sizes (e.g. /dev/sda1 with block size 4096 and
/dev/sdb1 with 512). In such case it leads to setting the blocksize of
swapped off device with wrong blocksize.
The bug can be triggered with multiple concurrent swapoff and swapon:
0. Swap for some device is on.
1. swapoff:
First the swapoff is called on this device and "struct swap_info_struct
*p" is assigned. This is done under swap_lock however this lock is
released for the call try_to_unuse().
2. swapon:
After the assignment above (and before acquiring swapon_mutex &
swap_lock by swapoff) the swapon is called on the same device.
The p->old_block_size is assigned to the value of block_size the device.
This block size should be the same as previous but sometimes it is not.
The swapon ends successfully.
3. swapoff:
Swapoff resumes, grabs the locks and mutex and continues to disable this
swap device. Now it sets the block size to value taken from swap_info
which was overwritten by swapon in 2.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Reported-by: Weijie Yang <weijie.yang.kh@xxxxxxxxx>
Cc: Bob Liu <bob.liu@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/swapfile.c~swap-fix-set_blocksize-race-during-swapon-swapoff mm/swapfile.c
--- a/mm/swapfile.c~swap-fix-set_blocksize-race-during-swapon-swapoff
+++ a/mm/swapfile.c
@@ -1824,6 +1824,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
struct filename *pathname;
int i, type, prev;
int err;
+ unsigned int old_block_size;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -1914,6 +1915,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
}
swap_file = p->swap_file;
+ old_block_size = p->old_block_size;
p->swap_file = NULL;
p->max = 0;
swap_map = p->swap_map;
@@ -1938,7 +1940,7 @@ SYSCALL_DEFINE1(swapoff, const char __us
inode = mapping->host;
if (S_ISBLK(inode->i_mode)) {
struct block_device *bdev = I_BDEV(inode);
- set_blocksize(bdev, p->old_block_size);
+ set_blocksize(bdev, old_block_size);
blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
} else {
mutex_lock(&inode->i_mutex);
_
Patches currently in -mm which might be from k.kozlowski@xxxxxxxxxxx are
origin.patch
frontswap-enable-call-to-invalidate-area-on-swapoff.patch
swap-fix-setting-page_size-blocksize-during-swapoff-swapon-race.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
