talos-obmc-linux/block, branch v4.4.16

block: partition: initialize percpuref before sending out KOBJ_ADD

2016-05-04T21:48:39+00:00

commit b30a337ca27c4f40439e4bfb290cba5f88d73bb7 upstream. The initialization of partition's percpu_ref should have been done before sending out KOBJ_ADD uevent, which may cause userspace to read partition table. So the uninitialized percpu_ref may be accessed in data path. This patch fixes this issue reported by Naveen. Reported-by: Naveen Kaje Tested-by: Naveen Kaje Fixes: 6c71013ecb7e2(block: partition: convert percpu ref) Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

dm: fix excessive dm-mq context switching

2016-04-12T16:08:40+00:00

commit 6acfe68bac7e6f16dc312157b1fa6e2368985013 upstream. Request-based DM's blk-mq support (dm-mq) was reported to be 50% slower than if an underlying null_blk device were used directly. One of the reasons for this drop in performance is that blk_insert_clone_request() was calling blk_mq_insert_request() with @async=true. This forced the use of kblockd_schedule_delayed_work_on() to run the blk-mq hw queues which ushered in ping-ponging between process context (fio in this case) and kblockd's kworker to submit the cloned request. The ftrace function_graph tracer showed: kworker-2013 => fio-12190 fio-12190 => kworker-2013 ... kworker-2013 => fio-12190 fio-12190 => kworker-2013 ... Fixing blk_insert_clone_request()'s blk_mq_insert_request() call to _not_ use kblockd to submit the cloned requests isn't enough to eliminate the observed context switches. In addition to this dm-mq specific blk-core fix, there are 2 DM core fixes to dm-mq that (when paired with the blk-core fix) completely eliminate the observed context switching: 1) don't blk_mq_run_hw_queues in blk-mq request completion Motivated by desire to reduce overhead of dm-mq, punting to kblockd just increases context switches. In my testing against a really fast null_blk device there was no benefit to running blk_mq_run_hw_queues() on completion (and no other blk-mq driver does this). So hopefully this change doesn't induce the need for yet another revert like commit 621739b00e16ca2d ! 2) use blk_mq_complete_request() in dm_complete_request() blk_complete_request() doesn't offer the traditional q->mq_ops vs .request_fn branching pattern that other historic block interfaces do (e.g. blk_get_request). Using blk_mq_complete_request() for blk-mq requests is important for performance. It should be noted that, like blk_complete_request(), blk_mq_complete_request() doesn't natively handle partial completions -- but the request-based DM-multipath target does provide the required partial completion support by dm.c:end_clone_bio() triggering requeueing of the request via dm-mpath.c:multipath_end_io()'s return of DM_ENDIO_REQUEUE. dm-mq fix #2 is _much_ more important than #1 for eliminating the context switches. Before: cpu : usr=15.10%, sys=59.39%, ctx=7905181, majf=0, minf=475 After: cpu : usr=20.60%, sys=79.35%, ctx=2008, majf=0, minf=472 With these changes multithreaded async read IOPs improved from ~950K to ~1350K for this dm-mq stacked on null_blk test-case. The raw read IOPs of the underlying null_blk device for the same workload is ~1950K. Fixes: 7fb4898e0 ("block: add blk-mq support to blk_insert_cloned_request()") Fixes: bfebd1cdb ("dm: add full blk-mq support to request-based DM") Reported-by: Sagi Grimberg Signed-off-by: Mike Snitzer Acked-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: Initialize max_dev_sectors to 0

2016-03-09T23:34:49+00:00

commit 5f009d3f8e6685fe8c6215082c1696a08b411220 upstream. The new queue limit is not used by the majority of block drivers, and should be initialized to 0 for the driver's requested settings to be used. Signed-off-by: Keith Busch Acked-by: Martin K. Petersen Reviewed-by: Sagi Grimberg Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bio: return EINTR if copying to user space got interrupted

2016-03-03T23:07:28+00:00

commit 2d99b55d378c996b9692a0c93dd25f4ed5d58934 upstream. Commit 35dc248383bbab0a7203fca4d722875bc81ef091 introduced a check for current->mm to see if we have a user space context and only copies data if we do. Now if an IO gets interrupted by a signal data isn't copied into user space any more (as we don't have a user space context) but user space isn't notified about it. This patch modifies the behaviour to return -EINTR from bio_uncopy_user() to notify userland that a signal has interrupted the syscall, otherwise it could lead to a situation where the caller may get a buffer with no data returned. This can be reproduced by issuing SG_IO ioctl()s in one thread while constantly sending signals to it. Fixes: 35dc248 [SCSI] sg: Fix user memory corruption when SG_IO is interrupted by a signal Signed-off-by: Johannes Thumshirn Signed-off-by: Hannes Reinecke Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: fix bio splitting on max sectors

2016-02-17T20:30:56+00:00

commit d0e5fbb01a67e400e82fefe4896ea40c6447ab98 upstream. After commit e36f62042880(block: split bios to maxpossible length), bio can be splitted in the middle of a vector entry, then it is easy to split out one bio which size isn't aligned with block size, especially when the block size is bigger than 512. This patch fixes the issue by making the max io size aligned to logical block size. Fixes: e36f62042880(block: split bios to maxpossible length) Reported-by: Stefan Haberland Cc: Keith Busch Suggested-by: Linus Torvalds Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: split bios to max possible length

2016-02-17T20:30:55+00:00

commit e36f6204288088fda50d1c84830340ccb70f85ff upstream. This splits bio in the middle of a vector to form the largest possible bio at the h/w's desired alignment, and guarantees the bio being split will have some data. The criteria for splitting is changed from the max sectors to the h/w's optimal sector alignment if it is provided. For h/w that advertise their block storage's underlying chunk size, it's a big performance win to not submit commands that cross them. If sector alignment is not provided, this patch uses the max sectors as before. This addresses the performance issue commit d380561113 attempted to fix, but was reverted due to splitting logic error. Signed-off-by: Keith Busch Cc: Jens Axboe Cc: Ming Lei Cc: Kent Overstreet Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

Revert "block: Split bios on chunk boundaries"

2016-01-08T16:00:29+00:00

This reverts commit d3805611130af9b911e908af9f67a3f64f4f0914. If we end up splitting on the first segment, we don't adjust the sector count. That results in hitting a BUG() with attempting to split 0 sectors. As this is just a performance issue and not a regression since 4.3 release, let's just rever this change. That gives us more time to test a real fix for 4.5, which would be marked for stable anyway.

block: add blk_start_queue_async()

2015-12-28T20:07:07+00:00

We currently only have an inline/sync helper to restart a stopped queue. If drivers need an async version, they have to roll their own. Add a generic helper instead. Signed-off-by: Jens Axboe

block: Split bios on chunk boundaries

2015-12-23T00:19:25+00:00

For h/w that advertise their block storage's underlying chunk size, it's a big performance win to not submit commands that cross them. This patch uses that criteria if it is provided. If it is not provided, this patch uses the max sectors as before. Signed-off-by: Keith Busch Signed-off-by: Jens Axboe

Merge branch 'for-linus' of git://git.kernel.dk/linux-block

2015-12-23T00:00:25+00:00

Pull block layer fixes from Jens Axboe: "Three small fixes for 4.4 final. Specifically: - The segment issue fix from Junichi, where the old IO path does a bio limit split before potentially bouncing the pages. We need to do that in the right order, to ensure that limitations are met. - A NVMe surprise removal IO hang fix from Keith. - A use-after-free in null_blk, introduced by a previous patch in this series. From Mike Krinkin" * 'for-linus' of git://git.kernel.dk/linux-block: null_blk: fix use-after-free error block: ensure to split after potentially bouncing a bio NVMe: IO ending fixes on surprise removal