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authorLinus Torvalds <torvalds@linux-foundation.org>2015-09-02 13:10:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-02 13:10:25 -0700
commit1081230b748de8f03f37f80c53dfa89feda9b8de (patch)
tree7238d60e01f0843bad8f03b5d84e4220fbba5e76 /Documentation
parentdf910390e2db07a76c87f258475f6c96253cee6c (diff)
parent2ca495ac27d245513c11fed70591b1838250e240 (diff)
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Merge branch 'for-4.3/core' of git://git.kernel.dk/linux-block
Pull core block updates from Jens Axboe: "This first core part of the block IO changes contains: - Cleanup of the bio IO error signaling from Christoph. We used to rely on the uptodate bit and passing around of an error, now we store the error in the bio itself. - Improvement of the above from myself, by shrinking the bio size down again to fit in two cachelines on x86-64. - Revert of the max_hw_sectors cap removal from a revision again, from Jeff Moyer. This caused performance regressions in various tests. Reinstate the limit, bump it to a more reasonable size instead. - Make /sys/block/<dev>/queue/discard_max_bytes writeable, by me. Most devices have huge trim limits, which can cause nasty latencies when deleting files. Enable the admin to configure the size down. We will look into having a more sane default instead of UINT_MAX sectors. - Improvement of the SGP gaps logic from Keith Busch. - Enable the block core to handle arbitrarily sized bios, which enables a nice simplification of bio_add_page() (which is an IO hot path). From Kent. - Improvements to the partition io stats accounting, making it faster. From Ming Lei. - Also from Ming Lei, a basic fixup for overflow of the sysfs pending file in blk-mq, as well as a fix for a blk-mq timeout race condition. - Ming Lin has been carrying Kents above mentioned patches forward for a while, and testing them. Ming also did a few fixes around that. - Sasha Levin found and fixed a use-after-free problem introduced by the bio->bi_error changes from Christoph. - Small blk cgroup cleanup from Viresh Kumar" * 'for-4.3/core' of git://git.kernel.dk/linux-block: (26 commits) blk: Fix bio_io_vec index when checking bvec gaps block: Replace SG_GAPS with new queue limits mask block: bump BLK_DEF_MAX_SECTORS to 2560 Revert "block: remove artifical max_hw_sectors cap" blk-mq: fix race between timeout and freeing request blk-mq: fix buffer overflow when reading sysfs file of 'pending' Documentation: update notes in biovecs about arbitrarily sized bios block: remove bio_get_nr_vecs() fs: use helper bio_add_page() instead of open coding on bi_io_vec block: kill merge_bvec_fn() completely md/raid5: get rid of bio_fits_rdev() md/raid5: split bio for chunk_aligned_read block: remove split code in blkdev_issue_{discard,write_same} btrfs: remove bio splitting and merge_bvec_fn() calls bcache: remove driver private bio splitting code block: simplify bio_add_page() block: make generic_make_request handle arbitrarily sized bios blk-cgroup: Drop unlikely before IS_ERR(_OR_NULL) block: don't access bio->bi_error after bio_put() block: shrink struct bio down to 2 cache lines again ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/block/biodoc.txt2
-rw-r--r--Documentation/block/biovecs.txt10
-rw-r--r--Documentation/block/queue-sysfs.txt10
3 files changed, 19 insertions, 3 deletions
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index fd12c0d835fd..5be8a7f4cc7f 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -1109,7 +1109,7 @@ it will loop and handle as many sectors (on a bio-segment granularity)
as specified.
Now bh->b_end_io is replaced by bio->bi_end_io, but most of the time the
-right thing to use is bio_endio(bio, uptodate) instead.
+right thing to use is bio_endio(bio) instead.
If the driver is dropping the io_request_lock from its request_fn strategy,
then it just needs to replace that with q->queue_lock instead.
diff --git a/Documentation/block/biovecs.txt b/Documentation/block/biovecs.txt
index 74a32ad52f53..25689584e6e0 100644
--- a/Documentation/block/biovecs.txt
+++ b/Documentation/block/biovecs.txt
@@ -24,7 +24,7 @@ particular, presenting the illusion of partially completed biovecs so that
normal code doesn't have to deal with bi_bvec_done.
* Driver code should no longer refer to biovecs directly; we now have
- bio_iovec() and bio_iovec_iter() macros that return literal struct biovecs,
+ bio_iovec() and bio_iter_iovec() macros that return literal struct biovecs,
constructed from the raw biovecs but taking into account bi_bvec_done and
bi_size.
@@ -109,3 +109,11 @@ Other implications:
over all the biovecs in the new bio - which is silly as it's not needed.
So, don't use bi_vcnt anymore.
+
+ * The current interface allows the block layer to split bios as needed, so we
+ could eliminate a lot of complexity particularly in stacked drivers. Code
+ that creates bios can then create whatever size bios are convenient, and
+ more importantly stacked drivers don't have to deal with both their own bio
+ size limitations and the limitations of the underlying devices. Thus
+ there's no need to define ->merge_bvec_fn() callbacks for individual block
+ drivers.
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 3a29f8914df9..e5d914845be6 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -20,7 +20,7 @@ This shows the size of internal allocation of the device in bytes, if
reported by the device. A value of '0' means device does not support
the discard functionality.
-discard_max_bytes (RO)
+discard_max_hw_bytes (RO)
----------------------
Devices that support discard functionality may have internal limits on
the number of bytes that can be trimmed or unmapped in a single operation.
@@ -29,6 +29,14 @@ number of bytes that can be discarded in a single operation. Discard
requests issued to the device must not exceed this limit. A discard_max_bytes
value of 0 means that the device does not support discard functionality.
+discard_max_bytes (RW)
+----------------------
+While discard_max_hw_bytes is the hardware limit for the device, this
+setting is the software limit. Some devices exhibit large latencies when
+large discards are issued, setting this value lower will make Linux issue
+smaller discards and potentially help reduce latencies induced by large
+discard operations.
+
discard_zeroes_data (RO)
------------------------
When read, this file will show if the discarded block are zeroed by the