BMC/Intel-BMC/linux.git/block/blk-flush.c, branch dev-4.17

blk-mq: don't allocate driver tag upfront for flush rq

2017-11-04T18:40:13+00:00

The idea behind it is simple: 1) for none scheduler, driver tag has to be borrowed for flush rq, otherwise we may run out of tag, and that causes an IO hang. And get/put driver tag is actually noop for none, so reordering tags isn't necessary at all. 2) for a real I/O scheduler, we need not allocate a driver tag upfront for flush rq. It works just fine to follow the same approach as normal requests: allocate driver tag for each rq just before calling ->queue_rq(). One driver visible change is that the driver tag isn't shared in the flush request sequence. That won't be a problem, since we always do that in legacy path. Then flush rq need not be treated specially wrt. get/put driver tag. This cleans up the code - for instance, reorder_tags_to_front() can be removed, and we needn't worry about request ordering in dispatch list for avoiding I/O deadlock. Also we have to put the driver tag before requeueing. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

blk-flush: use blk_mq_request_bypass_insert()

2017-11-04T18:38:40+00:00

In the following patch, we will use RQF_FLUSH_SEQ to decide: 1) if the flag isn't set, the flush rq need to be inserted via blk_insert_flush() 2) otherwise, the flush rq need to be dispatched directly since it is in flush machinery now. So we use blk_mq_request_bypass_insert() for requests of bypassing flush machinery, just like the legacy path did. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

blk-flush: don't run queue for requests bypassing flush

2017-11-04T18:38:40+00:00

blk_insert_flush() should only insert request since run queue always follows it. In case of bypassing flush, we don't need to run queue because every blk_insert_flush() follows one run queue. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: update comments to reflect REQ_FLUSH -> REQ_PREFLUSH rename

2017-08-25T16:36:54+00:00

Normally I wouldn't bother with this, but in my opinion the comments are the most important part of this whole file since without them no one would have any clue how this insanity works. Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe

block: replace bi_bdev with a gendisk pointer and partitions index

2017-08-23T18:49:55+00:00

This way we don't need a block_device structure to submit I/O. The block_device has different life time rules from the gendisk and request_queue and is usually only available when the block device node is open. Other callers need to explicitly create one (e.g. the lightnvm passthrough code, or the new nvme multipathing code). For the actual I/O path all that we need is the gendisk, which exists once per block device. But given that the block layer also does partition remapping we additionally need a partition index, which is used for said remapping in generic_make_request. Note that all the block drivers generally want request_queue or sometimes the gendisk, so this removes a layer of indirection all over the stack. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: Check locking assumptions at runtime

2017-06-21T01:27:14+00:00

Instead of documenting the locking assumptions of most block layer functions as a comment, use lockdep_assert_held() to verify locking assumptions at runtime. Signed-off-by: Bart Van Assche Reviewed-by: Christoph Hellwig Cc: Hannes Reinecke Cc: Omar Sandoval Cc: Ming Lei Signed-off-by: Jens Axboe

block: introduce new block status code type

2017-06-09T15:27:32+00:00

Currently we use nornal Linux errno values in the block layer, and while we accept any error a few have overloaded magic meanings. This patch instead introduces a new blk_status_t value that holds block layer specific status codes and explicitly explains their meaning. Helpers to convert from and to the previous special meanings are provided for now, but I suspect we want to get rid of them in the long run - those drivers that have a errno input (e.g. networking) usually get errnos that don't know about the special block layer overloads, and similarly returning them to userspace will usually return somethings that strictly speaking isn't correct for file system operations, but that's left as an exercise for later. For now the set of errors is a very limited set that closely corresponds to the previous overloaded errno values, but there is some low hanging fruite to improve it. blk_status_t (ab)uses the sparse __bitwise annotations to allow for sparse typechecking, so that we can easily catch places passing the wrong values. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: make __blk_end_bidi_request private

2017-04-19T16:19:47+00:00

blk_insert_flush should be using __blk_end_request to start with. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: remove outdated part of blkdev_issue_flush() comment

2017-03-24T21:41:30+00:00

blkdev_issue_flush() is now always synchronous, and it no longer has a flags argument. So remove the part of the comment about the WAIT flag. Signed-off-by: Eric Biggers Signed-off-by: Jens Axboe

block: don't defer flushes on blk-mq + scheduling

2017-02-17T19:35:47+00:00

For blk-mq with scheduling, we can potentially end up with ALL driver tags assigned and sitting on the flush queues. If we defer because of an inlfight data request, then we can deadlock if that data request doesn't already have a tag assigned. This fixes a deadlock with running the xfs/297 xfstest, where thousands of syncs can cause the drive queue to stall. Signed-off-by: Jens Axboe Reviewed-by: Omar Sandoval