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Linux kernel
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Pinned pages shouldn't be write-protected when fork() happens, because
follow up copy-on-write on these pages could cause the pinned pages to
be replaced by random newly allocated pages.
For huge PMDs, we split the huge pmd if pinning is detected. So that
future handling will be done by the PTE level (with our latest changes,
each of the small pages will be copied). We can achieve this by let
copy_huge_pmd() return -EAGAIN for pinned pages, so that we'll
fallthrough in copy_pmd_range() and finally land the next
copy_pte_range() call.
Huge PUDs will be even more special - so far it does not support
anonymous pages. But it can actually be done the same as the huge PMDs
even if the split huge PUDs means to erase the PUD entries. It'll
guarantee the follow up fault ins will remap the same pages in either
parent/child later.
This might not be the most efficient way, but it should be easy and
clean enough. It should be fine, since we're tackling with a very rare
case just to make sure userspaces that pinned some thps will still work
even without MADV_DONTFORK and after they fork()ed.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This allows copy_pte_range() to do early cow if the pages were pinned on
the source mm.
Currently we don't have an accurate way to know whether a page is pinned
or not. The only thing we have is page_maybe_dma_pinned(). However
that's good enough for now. Especially, with the newly added
mm->has_pinned flag to make sure we won't affect processes that never
pinned any pages.
It would be easier if we can do GFP_KERNEL allocation within
copy_one_pte(). Unluckily, we can't because we're with the page table
locks held for both the parent and child processes. So the page
allocation needs to be done outside copy_one_pte().
Some trick is there in copy_present_pte(), majorly the wrprotect trick
to block concurrent fast-gup. Comments in the function should explain
better in place.
Oleg Nesterov reported a (probably harmless) bug during review that we
didn't reset entry.val properly in copy_pte_range() so that potentially
there's chance to call add_swap_count_continuation() multiple times on
the same swp entry. However that should be harmless since even if it
happens, the same function (add_swap_count_continuation()) will return
directly noticing that there're enough space for the swp counter. So
instead of a standalone stable patch, it is touched up in this patch
directly.
Link: https://lore.kernel.org/lkml/20200914143829.GA1424636@nvidia.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This prepares for the future work to trigger early cow on pinned pages
during fork().
No functional change intended.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(Commit message majorly collected from Jason Gunthorpe)
Reduce the chance of false positive from page_maybe_dma_pinned() by
keeping track if the mm_struct has ever been used with pin_user_pages().
This allows cases that might drive up the page ref_count to avoid any
penalty from handling dma_pinned pages.
Future work is planned, to provide a more sophisticated solution, likely
to turn it into a real counter. For now, make it atomic_t but use it as
a boolean for simplicity.
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull SCSI fixes from James Bottomley:
"Three fixes: one in drivers (lpfc) and two for zoned block devices.
The latter also impinges on the block layer but only to introduce a
new block API for setting the zone model rather than fiddling with the
queue directly in the zoned block driver"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: sd: sd_zbc: Fix ZBC disk initialization
scsi: sd: sd_zbc: Fix handling of host-aware ZBC disks
scsi: lpfc: Fix initial FLOGI failure due to BBSCN not supported
Pull io_uring fixes from Jens Axboe:
"Two fixes for regressions in this cycle, and one that goes to 5.8
stable:
- fix leak of getname() retrieved filename
- remove plug->nowait assignment, fixing a regression with btrfs
- fix for async buffered retry"
* tag 'io_uring-5.9-2020-09-25' of git://git.kernel.dk/linux-block:
io_uring: ensure async buffered read-retry is setup properly
io_uring: don't unconditionally set plug->nowait = true
io_uring: ensure open/openat2 name is cleaned on cancelation
Make sure to call sd_zbc_init_disk() when the sdkp->zoned field is known,
that is, once sd_read_block_characteristics() is executed in
sd_revalidate_disk(), so that host-aware disks also get initialized. To do
so, move sd_zbc_init_disk() call in sd_zbc_revalidate_zones() and make sure
to execute it for all zoned disks, including for host-aware disks used as
regular disks as these disk zoned model may be changed back to BLK_ZONED_HA
when partitions are deleted.
Link: https://lore.kernel.org/r/20200915073347.832424-3-damien.lemoal@wdc.com
Fixes: 5795eb443060 ("scsi: sd_zbc: emulate ZONE_APPEND commands")
Cc: <stable@vger.kernel.org> # v5.8+
Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull block fixes from Jens Axboe:
"NVMe pull request from Christoph, and removal of a dead define.
- fix error during controller probe that cause double free irqs
(Keith Busch)
- FC connection establishment fix (James Smart)
- properly handle completions for invalid tags (Xianting Tian)
- pass the correct nsid to the command effects and supported log
(Chaitanya Kulkarni)"
* tag 'block-5.9-2020-09-25' of git://git.kernel.dk/linux-block:
block: remove unused BLK_QC_T_EAGAIN flag
nvme-core: don't use NVME_NSID_ALL for command effects and supported log
nvme-fc: fail new connections to a deleted host or remote port
nvme-pci: fix NULL req in completion handler
nvme: return errors for hwmon init
A previous commit for fixing up short reads botched the async retry
path, so we ended up going to worker threads more often than we should.
Fix this up, so retries work the way they originally were intended to.
Fixes: 227c0c9673d8 ("io_uring: internally retry short reads")
Reported-by: Hao_Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When CONFIG_BLK_DEV_ZONED is disabled, allow using host-aware ZBC disks as
regular disks. In this case, ensure that command completion is correctly
executed by changing sd_zbc_complete() to return good_bytes instead of 0
and causing a hang during device probe (endless retries).
When CONFIG_BLK_DEV_ZONED is enabled and a host-aware disk is detected to
have partitions, it will be used as a regular disk. In this case, make sure
to not do anything in sd_zbc_revalidate_zones() as that triggers warnings.
Since all these different cases result in subtle settings of the disk queue
zoned model, introduce the block layer helper function
blk_queue_set_zoned() to generically implement setting up the effective
zoned model according to the disk type, the presence of partitions on the
disk and CONFIG_BLK_DEV_ZONED configuration.
Link: https://lore.kernel.org/r/20200915073347.832424-2-damien.lemoal@wdc.com
Fixes: b72053072c0b ("block: allow partitions on host aware zone devices")
Cc: <stable@vger.kernel.org>
Reported-by: Borislav Petkov <bp@alien8.de>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull s390 fix from Vasily Gorbik:
"Fix truncated ZCRYPT_PERDEV_REQCNT ioctl result. Copy entire reqcnt
list"
* tag 's390-5.9-7' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
s390/zcrypt: Fix ZCRYPT_PERDEV_REQCNT ioctl
commit 7b6620d7db56 ("block: remove REQ_NOWAIT_INLINE") removed the
REQ_NOWAIT_INLINE related code, but the diff wasn't applied to
blk_types.h somehow.
Then commit 2771cefeac49 ("block: remove the REQ_NOWAIT_INLINE flag")
removed the REQ_NOWAIT_INLINE flag while the BLK_QC_T_EAGAIN flag still
remains.
Fixes: 7b6620d7db56 ("block: remove REQ_NOWAIT_INLINE")
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This causes all the bios to be submitted with REQ_NOWAIT, which can be
problematic on either btrfs or on file systems that otherwise use a mix
of block devices where only some of them support it.
For now, just remove the setting of plug->nowait = true.
Reported-by: Dan Melnic <dmm@fb.com>
Reported-by: Brian Foster <bfoster@redhat.com>
Fixes: b63534c41e20 ("io_uring: re-issue block requests that failed because of resources")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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