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SeongJae Park 50de69fd6e xen/blkback: Avoid unmapping unmapped grant pages 
[ Upstream commit f9bd84a8a8 ]

For each I/O request, blkback first maps the foreign pages for the
request to its local pages.  If an allocation of a local page for the
mapping fails, it should unmap every mapping already made for the
request.

However, blkback's handling mechanism for the allocation failure does
not mark the remaining foreign pages as unmapped.  Therefore, the unmap
function merely tries to unmap every valid grant page for the request,
including the pages not mapped due to the allocation failure.  On a
system that fails the allocation frequently, this problem leads to
following kernel crash.

  [  372.012538] BUG: unable to handle kernel NULL pointer dereference at 0000000000000001
  [  372.012546] IP: [<ffffffff814071ac>] gnttab_unmap_refs.part.7+0x1c/0x40
  [  372.012557] PGD 16f3e9067 PUD 16426e067 PMD 0
  [  372.012562] Oops: 0002 [#1] SMP
  [  372.012566] Modules linked in: act_police sch_ingress cls_u32
  ...
  [  372.012746] Call Trace:
  [  372.012752]  [<ffffffff81407204>] gnttab_unmap_refs+0x34/0x40
  [  372.012759]  [<ffffffffa0335ae3>] xen_blkbk_unmap+0x83/0x150 [xen_blkback]
  ...
  [  372.012802]  [<ffffffffa0336c50>] dispatch_rw_block_io+0x970/0x980 [xen_blkback]
  ...
  Decompressing Linux... Parsing ELF... done.
  Booting the kernel.
  [    0.000000] Initializing cgroup subsys cpuset

This commit fixes this problem by marking the grant pages of the given
request that didn't mapped due to the allocation failure as invalid.

Fixes: c6cc142dac ("xen-blkback: use balloon pages for all mappings")

Reviewed-by: David Woodhouse <dwmw@amazon.de>
Reviewed-by: Maximilian Heyne <mheyne@amazon.de>
Reviewed-by: Paul Durrant <pdurrant@amazon.co.uk>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-01-09 10:20:07 +01:00
..
aoe block: aoe: Fix kernel crash due to atomic sleep when exiting 2019-08-08 07:29:02 -06:00
drbd block: drbd: remove a stray unlock in __drbd_send_protocol() 2019-11-08 06:55:22 -07:00
mtip32xx block: mtip32xx: Remove call to memset after dma_alloc_coherent 2019-06-29 09:42:50 -06:00
paride paride/pcd: need to check if cd->disk is null in pcd_detect 2019-09-04 07:04:37 -06:00
rsxx rsxx: add missed destroy_workqueue calls in remove 2019-11-14 13:59:49 -07:00
xen-blkback xen/blkback: Avoid unmapping unmapped grant pages 2020-01-09 10:20:07 +01:00
zram zram: fix race between backing_dev_show and backing_dev_store 2019-10-19 06:32:32 -04:00
Kconfig docs: blockdev: add it to the admin-guide 2019-07-15 11:03:01 -03:00
Makefile drivers/block: Remove DAC960 driver 2018-10-17 09:42:30 -06:00
amiflop.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
ataflop.c ataflop: Mark expected switch fall-through 2019-07-29 15:24:58 -06:00
brd.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
cryptoloop.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 30 2019-05-24 17:27:10 +02:00
floppy.c floppy: fix usercopy direction 2019-08-09 07:41:36 -06:00
loop.c loop: fix no-unmap write-zeroes request behavior 2019-12-31 16:44:31 +01:00
loop.h block/loop: Use global lock for ioctl() operation. 2018-11-08 06:30:11 -07:00
nbd.c nbd: fix shutdown and recv work deadlock v2 2019-12-31 16:46:34 +01:00
null_blk.h null_blk: format pr_* logs with pr_fmt 2019-09-16 08:38:29 -06:00
null_blk_main.c null_blk: format pr_* logs with pr_fmt 2019-09-16 08:38:29 -06:00
null_blk_zoned.c null_blk: Fix zoned command return code 2019-10-09 21:00:20 -06:00
pktcdvd.c pktcdvd: remove warning on attempting to register non-passthrough dev 2019-09-22 10:01:05 -06:00
ps3disk.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 164 2019-05-30 11:26:38 -07:00
ps3vram.c block/ps3vram: Use %llu to format sector_t after LBDAF removal 2019-06-13 03:17:50 -06:00
rbd.c rbd: silence bogus uninitialized warning in rbd_object_map_update_finish() 2019-11-14 19:00:53 +01:00
rbd_types.h rbd: support for object-map and fast-diff 2019-07-08 14:01:45 +02:00
skd_main.c Linux 5.2-rc6 2019-07-01 08:16:08 -06:00
skd_s1120.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 497 2019-06-19 17:09:53 +02:00
sunvdc.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
swim.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
swim3.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
swim_asm.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sx8.c sx8: use a per-host tag_set 2018-11-09 08:14:14 -07:00
umem.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 349 2019-06-05 17:37:08 +02:00
umem.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 348 2019-06-05 17:37:08 +02:00
virtio_blk.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
xen-blkfront.c xen-blkfront: switch kcalloc to kvcalloc for large array allocation 2019-06-03 22:16:19 -04:00
xsysace.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
z2ram.c powerpc updates for 4.20 2018-10-26 14:36:21 -07:00