linux/drivers/block
Ross Zwisler 1d037577c3 loop: Fix lost writes caused by missing flag
The following commit:

commit aa4d86163e ("block: loop: switch to VFS ITER_BVEC")

replaced __do_lo_send_write(), which used ITER_KVEC iterators, with
lo_write_bvec() which uses ITER_BVEC iterators.  In this change, though,
the WRITE flag was lost:

-       iov_iter_kvec(&from, ITER_KVEC | WRITE, &kvec, 1, len);
+       iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len);

This flag is necessary for the DAX case because we make decisions based on
whether or not the iterator is a READ or a WRITE in dax_iomap_actor() and
in dax_iomap_rw().

We end up going through this path in configurations where we combine a PMEM
device with 4k sectors, a loopback device and DAX.  The consequence of this
missed flag is that what we intend as a write actually turns into a read in
the DAX code, so no data is ever written.

The very simplest test case is to create a loopback device and try and
write a small string to it, then hexdump a few bytes of the device to see
if the write took.  Without this patch you read back all zeros, with this
you read back the string you wrote.

For XFS this causes us to fail or panic during the following xfstests:

	xfs/074 xfs/078 xfs/216 xfs/217 xfs/250

For ext4 we have a similar issue where writes never happen, but we don't
currently have any xfstests that use loopback and show this issue.

Fix this by restoring the WRITE flag argument to iov_iter_bvec().  This
causes the xfstests to all pass.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Fixes: commit aa4d86163e ("block: loop: switch to VFS ITER_BVEC")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-03-09 08:36:36 -07:00
..
aoe aoe: use ktime_t instead of timeval 2018-01-17 08:41:07 -07:00
drbd Merge branch 'work.sock_recvmsg' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-01-30 18:59:03 -08:00
mtip32xx Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
paride Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block 2017-11-14 15:32:19 -08:00
rsxx treewide: setup_timer() -> timer_setup() (2 field) 2017-11-21 15:57:09 -08:00
xen-blkback Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block 2017-09-07 11:59:42 -07:00
zram block: convert to bio_first_bvec_all & bio_first_page_all 2018-01-06 09:18:00 -07:00
DAC960.c pci-v4.16-changes 2018-02-06 09:59:40 -08:00
DAC960.h block: DAC960: Replace PCI pool old API 2018-01-02 16:09:50 -06:00
Kconfig null_blk: remove explicit 'select FAULT_INJECTION' 2018-01-11 07:58:31 -07:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
amiflop.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
ataflop.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
brd.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
cryptoloop.c block: cryptoloop - Fix build warning 2017-09-26 07:41:22 -06:00
floppy.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
loop.c loop: Fix lost writes caused by missing flag 2018-03-09 08:36:36 -07:00
loop.h block/loop: make loop cgroup aware 2017-09-26 07:41:22 -06:00
nbd.c nbd: fix return value in error handling path 2018-02-27 15:51:37 -07:00
null_blk.c blk-mq: introduce BLK_STS_DEV_RESOURCE 2018-01-30 20:18:28 -07:00
pktcdvd.c block: fix a typo 2018-03-01 08:41:27 -07:00
ps3disk.c block: introduce new block status code type 2017-06-09 09:27:32 -06:00
ps3vram.c block/ps3vram: Check return of ps3vram_cache_init 2017-08-17 23:03:44 +10:00
rbd.c rbd: whitelist RBD_FEATURE_OPERATIONS feature bit 2018-01-29 18:36:03 +01:00
rbd_types.h rbd: RBD_V{1,2}_DATA_FORMAT macros 2017-02-20 12:16:15 +01:00
skd_main.c block: skd: fix incorrect linux/slab_def.h inclusion 2018-02-02 08:07:45 -07:00
skd_s1120.h skd: Use __packed only when needed 2017-08-18 08:45:29 -06:00
sunvdc.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
swim.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
swim3.c treewide: Remove TIMER_FUNC_TYPE and TIMER_DATA_TYPE casts 2017-11-21 16:35:54 -08:00
swim_asm.S
sx8.c block: introduce new block status code type 2017-06-09 09:27:32 -06:00
umem.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
umem.h
virtio_blk.c virtio, vhost: fixes, cleanups, features 2018-02-08 10:41:00 -08:00
xen-blkfront.c Merge branch 'stable/for-jens-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-linus 2018-03-08 09:24:52 -07:00
xsysace.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
z2ram.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00