This makes it available outside of blk-merge.c, and inlining such a trivial
helper seems pretty useful to start with.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

I noticed that when booting with a default blk-mq I/O scheduler, the
/sys/block/*/queue/iosched directory was missing. However, switching
after boot did create the directory. This is because we skip the initial
elevator register/unregister when we don't have a ->request_fn(), but we
should still do it for the ->mq_ops case.
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

If we end up doing a request-to-request merge when we have completed
a bio-to-request merge, we free the request from deep down in that
path. For blk-mq-sched, the merge path has to hold the appropriate
lock, but we don't need it for freeing the request. And in fact
holding the lock is problematic, since we are now calling the
mq sched put_rq_private() hook with the lock held. Other call paths
do not hold this lock.

Fix this inconsistency by ensuring that the caller frees a merged
request. Then we can do it outside of the lock, making it both more
efficient and fixing the blk-mq-sched problem of invoking parts of
the scheduler with an unknown lock state.
Reported-by: NPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>

When we attempt to merge request-to-request, we return a 0/1 if we
ended up merging or not. Change that to return the pointer to the
request that we freed. We will use this to move the freeing of
that request out of the merge logic, so that callers can drop
locks before freeing the request.

There should be no functional changes in this patch.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>

If blkg_create fails, new_blkg passed as an argument will
be freed by blkg_create, so there is no need to free it again.
Signed-off-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

There's a weird inconsistency that flushes are mostly hidden from the
scheduler, but it needs to be aware of them in ->insert_requests().
Instead of having every scheduler call blk_mq_sched_bypass_insert(),
let's do it in the common framework.
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This needs to happen after we tear down blktrace.
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

When I added the blk-mq debugging information to debugfs, I didn't
notice that blktrace also creates a "block" directory in debugfs. Make
them use the same dentry, now created in the core block code. Based on a
patch from Jens.
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Warnings of the following form occur because scsi reuses a devt number
while the block layer still has it referenced as the name of the bdi
[1]:

 WARNING: CPU: 1 PID: 93 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x62/0x80
 sysfs: cannot create duplicate filename '/devices/virtual/bdi/8:192'
 [..]
 Call Trace:
  dump_stack+0x86/0xc3
  __warn+0xcb/0xf0
  warn_slowpath_fmt+0x5f/0x80
  ? kernfs_path_from_node+0x4f/0x60
  sysfs_warn_dup+0x62/0x80
  sysfs_create_dir_ns+0x77/0x90
  kobject_add_internal+0xb2/0x350
  kobject_add+0x75/0xd0
  device_add+0x15a/0x650
  device_create_groups_vargs+0xe0/0xf0
  device_create_vargs+0x1c/0x20
  bdi_register+0x90/0x240
  ? lockdep_init_map+0x57/0x200
  bdi_register_owner+0x36/0x60
  device_add_disk+0x1bb/0x4e0
  ? __pm_runtime_use_autosuspend+0x5c/0x70
  sd_probe_async+0x10d/0x1c0
  async_run_entry_fn+0x39/0x170

This is a brute-force fix to pass the devt release information from
sd_probe() to the locations where we register the bdi,
device_add_disk(), and unregister the bdi, blk_cleanup_queue().

Thanks to Omar for the quick reproducer script [2]. This patch survives
where an unmodified kernel fails in a few seconds.

[1]: https://marc.info/?l=linux-scsi&m=147116857810716&w=4
[2]: http://marc.info/?l=linux-block&m=148554717109098&w=2

Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Reported-by: NOmar Sandoval <osandov@osandov.com>
Tested-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

blk_get_backing_dev_info() is now a simple dereference. Remove that
function and simplify some code around that.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currenly blk_get_backing_dev_info() is not safe to be called when the
block device is not open as bdev->bd_disk is NULL in that case. However
inode_to_bdi() uses this function and may be call called from flusher
worker or other writeback related functions without bdev being open
which leads to crashes such as:

[113031.075540] Unable to handle kernel paging request for data at address 0x00000000
[113031.075614] Faulting instruction address: 0xc0000000003692e0
0:mon> t
[c0000000fb65f900] c00000000036cb6c writeback_sb_inodes+0x30c/0x590
[c0000000fb65fa10] c00000000036ced4 __writeback_inodes_wb+0xe4/0x150
[c0000000fb65fa70] c00000000036d33c wb_writeback+0x30c/0x450
[c0000000fb65fb40] c00000000036e198 wb_workfn+0x268/0x580
[c0000000fb65fc50] c0000000000f3470 process_one_work+0x1e0/0x590
[c0000000fb65fce0] c0000000000f38c8 worker_thread+0xa8/0x660
[c0000000fb65fd80] c0000000000fc4b0 kthread+0x110/0x130
[c0000000fb65fe30] c0000000000098f0 ret_from_kernel_thread+0x5c/0x6c
Signed-off-by: NJens Axboe <axboe@fb.com>

Instead of storing backing_dev_info inside struct request_queue,
allocate it dynamically, reference count it, and free it when the last
reference is dropped. Currently only request_queue holds the reference
but in the following patch we add other users referencing
backing_dev_info.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

We will want to have struct backing_dev_info allocated separately from
struct request_queue. As the first step add pointer to backing_dev_info
to request_queue and convert all users touching it. No functional
changes in this patch.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently, block device inodes stay around after corresponding gendisk
hash died until memory reclaim finds them and frees them. Since we will
make block device inode pin the bdi, we want to free the block device
inode as soon as the device goes away so that bdi does not stay around
unnecessarily. Furthermore we need to avoid issues when new device with
the same major,minor pair gets created since reusing the bdi structure
would be rather difficult in this case.

Unhashing block device inode on gendisk destruction nicely deals with
these problems. Once last block device inode reference is dropped (which
may be directly in del_gendisk()), the inode gets evicted. Furthermore if
the major,minor pair gets reallocated, we are guaranteed to get new
block device inode even if old block device inode is not yet evicted and
thus we avoid issues with possible reuse of bdi.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Replace the two debugfs_create_file() loops by a call to the new
debugfs_create_files() function. Add an empty element at the end
of the two attribute arrays such that the array size does not have
to be passed to debugfs_create_files().
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Allow users to interrupt show operations instead of making a user
space process unkillable if ownership of q->sysfs_lock cannot be
obtained.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Avoid that sparse reports the following complaints:

block/elevator.c:541:29: warning: incorrect type in assignment (different base types)
block/elevator.c:541:29:    expected bool [unsigned] [usertype] next_sorted
block/elevator.c:541:29:    got restricted req_flags_t

block/blk-mq-debugfs.c:92:54: warning: cast from restricted req_flags_t
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch avoids that sparse complains about lock imbalances.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Instead of keeping two levels of indirection for requests types, fold it
all into the operations.  The little caveat here is that previously
cmd_type only applied to struct request, while the request and bio op
fields were set to plain REQ_OP_READ/WRITE even for passthrough
operations.

Instead this patch adds new REQ_OP_* for SCSI passthrough and driver
private requests, althought it has to add two for each so that we
can communicate the data in/out nature of the request.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

This can be used to check for fs vs non-fs requests and basically
removes all knowledge of BLOCK_PC specific from the block layer,
as well as preparing for removing the cmd_type field in struct request.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

We only need this code to support scsi, ide, cciss and virtio.  And at
least for virtio it's a deprecated feature to start with.

This should shrink the kernel size for embedded device that only use,
say eMMC a bit.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

These days we have the proper flags set since request allocation time.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

And require all drivers that want to support BLOCK_PC to allocate it
as the first thing of their private data.  To support this the legacy
IDE and BSG code is switched to set cmd_size on their queues to let
the block layer allocate the additional space.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

Simply the boilerplate code needed for bsg nodes a bit.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

This mirrors the blk-mq capabilities to allocate extra drivers-specific
data behind struct request by setting a cmd_size field, as well as having
a constructor / destructor for it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Return an errno value instead of the passed in queue so that the callers
don't have to keep track of two queues, and move the assignment of the
request_fn and lock to the caller as passing them as argument doesn't
simplify anything.  While we're at it also remove two pointless NULL
assignments, given that the request structure is zeroed on allocation.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

We can't initalize the elevator fields for flushes as flush share space
in struct request with the elevator data.  But currently we can't
communicate that a request is a flush through blk_get_request as we
can only pass READ or WRITE, and the low-level code looks at the
possible NULL bio to check for a flush.

Fix this by allowing to pass any block op and flags, and by checking for
the flush flags in __get_request.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This fixes a couple of problems:

1. In the !CONFIG_DEBUG_FS case, the stub definitions were bogus.
2. In the !CONFIG_BLOCK case, blk-mq-debugfs.c shouldn't be compiled at
   all.

Fix the stub definitions and add a CONFIG_BLK_DEBUG_FS Kconfig option.

Fixes: 07e4fead ("blk-mq: create debugfs directory tree")
Signed-off-by: NOmar Sandoval <osandov@fb.com>

Augment Kconfig description.
Signed-off-by: NJens Axboe <axboe@fb.com>

Use op_is_flush() where applicable.
Signed-off-by: NJens Axboe <axboe@fb.com>

Instead of letting the caller check this and handle the details
of inserting a flush request, put the logic in the scheduler
insertion function. This fixes direct flush insertion outside
of the usual make_request_fn calls, like from dm via
blk_insert_cloned_request().
Signed-off-by: NJens Axboe <axboe@fb.com>

This centralizes the checks for bios that needs to be go into the flush
state machine.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

When we invoke dispatch_requests(), the scheduler empties everything
into the passed in list. This isn't always a good thing, since it
means that we remove items that we could have potentially merged
with.

Change the function to dispatch single requests at the time. If
we do that, we can backoff exactly at the point where the device
can't consume more IO, and leave the rest with the scheduler for
better merging and future dispatch decision making.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Tested-by: NHannes Reinecke <hare@suse.com>

If we have both multiple hardware queues and shared tag map between
devices, we need to ensure that we propagate the hardware queue
restart bit higher up. This is because we can get into a situation
where we don't have any IO pending on a hardware queue, yet we fail
getting a tag to start new IO. If that happens, it's not enough to
mark the hardware queue as needing a restart, we need to bubble
that up to the higher level queue as well.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Tested-by: NHannes Reinecke <hare@suse.com>

We don't want to hold on to this resource when we have a scheduler
attached.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Tested-by: NHannes Reinecke <hare@suse.com>

Once we mark the queue as needing a restart, re-check if we can
get a driver tag. This fixes a theoretical issue where the needed
IO completes _after_ blk_mq_get_driver_tag() fails, but before we
manage to set the restart bit.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Tested-by: NHannes Reinecke <hare@suse.com>

We'll use the same criteria for whether we need to run the queue sync
or async when we have a scheduler, as we do without one.
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Tested-by: NHannes Reinecke <hare@suse.com>

These counters aren't as out-of-place in sysfs as the other stuff, but
debugfs is a slightly better home for them.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

These statistics _might_ be useful to userspace, but it's better not to
commit to an ABI for these yet. Also, the dispatched file in sysfs
couldn't be cleared, so make it clearable like the others in debugfs.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

These can be used to debug issues like tag leaks and stuck requests.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

These are very tied to the blk-mq tag implementation, so exposing them
to sysfs isn't a great idea. Move the debugging information to debugfs
and add basic entries for the number of tags and the number of reserved
tags to sysfs.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>