linux-stable.git/drivers/md/bcache/request.c, branch v4.9.76

bcache: fix wrong cache_misses statistics

2017-12-20T09:07:30+00:00

[ Upstream commit c157313791a999646901b3e3c6888514ebc36d62 ]

Currently, Cache missed IOs are identified by s->cache_miss, but actually,
there are many situations that missed IOs are not assigned a value for
s->cache_miss in cached_dev_cache_miss(), for example, a bypassed IO
(s->iop.bypass = 1), or the cache_bio allocate failed. In these situations,
it will go to out_put or out_submit, and s->cache_miss is null, which leads
bch_mark_cache_accounting() to treat this IO as a hit IO.

[ML: applied by 3-way merge]

Signed-off-by: tang.junhui 
Reviewed-by: Michael Lyle 
Reviewed-by: Coly Li 
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bcache: recover data from backing when data is clean

2017-12-09T21:01:46+00:00

commit e393aa2446150536929140739f09c6ecbcbea7f0 upstream.

When we send a read request and hit the clean data in cache device, there
is a situation called cache read race in bcache(see the commit in the tail
of cache_look_up(), the following explaination just copy from there):
The bucket we're reading from might be reused while our bio is in flight,
and we could then end up reading the wrong data. We guard against this
by checking (in bch_cache_read_endio()) if the pointer is stale again;
if so, we treat it as an error (s->iop.error = -EINTR) and reread from
the backing device (but we don't pass that error up anywhere)

It should be noted that cache read race happened under normal
circumstances, not the circumstance when SSD failed, it was counted
and shown in  /sys/fs/bcache/XXX/internal/cache_read_races.

Without this patch, when we use writeback mode, we will never reread from
the backing device when cache read race happened, until the whole cache
device is clean, because the condition
(s->recoverable && (dc && !atomic_read(&dc->has_dirty))) is false in
cached_dev_read_error(). In this situation, the s->iop.error(= -EINTR)
will be passed up, at last, user will receive -EINTR when it's bio end,
this is not suitable, and wield to up-application.

In this patch, we use s->read_dirty_data to judge whether the read
request hit dirty data in cache device, it is safe to reread data from
the backing device when the read request hit clean data. This can not
only handle cache read race, but also recover data when failed read
request from cache device.

[edited by mlyle to fix up whitespace, commit log title, comment
spelling]

Fixes: d59b23795933 ("bcache: only permit to recovery read error when cache device is clean")
Signed-off-by: Hua Rui 
Reviewed-by: Michael Lyle 
Reviewed-by: Coly Li 
Signed-off-by: Michael Lyle 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: only permit to recovery read error when cache device is clean

2017-12-09T21:01:46+00:00

commit d59b23795933678c9638fd20c942d2b4f3cd6185 upstream.

When bcache does read I/Os, for example in writeback or writethrough mode,
if a read request on cache device is failed, bcache will try to recovery
the request by reading from cached device. If the data on cached device is
not synced with cache device, then requester will get a stale data.

For critical storage system like database, providing stale data from
recovery may result an application level data corruption, which is
unacceptible.

With this patch, for a failed read request in writeback or writethrough
mode, recovery a recoverable read request only happens when cache device
is clean. That is to say, all data on cached device is up to update.

For other cache modes in bcache, read request will never hit
cached_dev_read_error(), they don't need this patch.

Please note, because cache mode can be switched arbitrarily in run time, a
writethrough mode might be switched from a writeback mode. Therefore
checking dc->has_data in writethrough mode still makes sense.

Changelog:
V4: Fix parens error pointed by Michael Lyle.
v3: By response from Kent Oversteet, he thinks recovering stale data is a
    bug to fix, and option to permit it is unnecessary. So this version
    the sysfs file is removed.
v2: rename sysfs entry from allow_stale_data_on_failure  to
    allow_stale_data_on_failure, and fix the confusing commit log.
v1: initial patch posted.

[small change to patch comment spelling by mlyle]

Signed-off-by: Coly Li 
Signed-off-by: Michael Lyle 
Reported-by: Arne Wolf 
Reviewed-by: Michael Lyle 
Cc: Kent Overstreet 
Cc: Nix 
Cc: Kai Krakow 
Cc: Eric Wheeler 
Cc: Junhui Tang 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: do not subtract sectors_to_gc for bypassed IO

2017-09-27T12:39:24+00:00

commit 69daf03adef5f7bc13e0ac86b4b8007df1767aab upstream.

Since bypassed IOs use no bucket, so do not subtract sectors_to_gc to
trigger gc thread.

Signed-off-by: tang.junhui 
Acked-by: Coly Li 
Reviewed-by: Eric Wheeler 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: Make gc wakeup sane, remove set_task_state()

2017-02-23T16:44:36+00:00

commit be628be09563f8f6e81929efbd7cf3f45c344416 upstream.

Signed-off-by: Kent Overstreet 
Cc: Coly Li 
Signed-off-by: Greg Kroah-Hartman

block: export bio_free_pages to other modules

2016-09-22T13:48:03+00:00

bio_free_pages is introduced in commit 1dfa0f68c040
("block: add a helper to free bio bounce buffer pages"),
we can reuse the func in other modules after it was
imported.

Cc: Christoph Hellwig 
Cc: Jens Axboe 
Cc: Mike Snitzer 
Cc: Shaohua Li 
Signed-off-by: Guoqing Jiang 
Acked-by: Kent Overstreet 
Signed-off-by: Jens Axboe

block: rename bio bi_rw to bi_opf

2016-08-07T20:41:02+00:00

Since commit 63a4cc24867d, bio->bi_rw contains flags in the lower
portion and the op code in the higher portions. This means that
old code that relies on manually setting bi_rw is most likely
going to be broken. Instead of letting that brokeness linger,
rename the member, to force old and out-of-tree code to break
at compile time instead of at runtime.

No intended functional changes in this commit.

Signed-off-by: Jens Axboe

block, drivers, fs: rename REQ_FLUSH to REQ_PREFLUSH

2016-06-07T19:41:38+00:00

To avoid confusion between REQ_OP_FLUSH, which is handled by
request_fn drivers, and upper layers requesting the block layer
perform a flush sequence along with possibly a WRITE, this patch
renames REQ_FLUSH to REQ_PREFLUSH.

Signed-off-by: Mike Christie 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

bcache: use bio op accessors

2016-06-07T19:41:38+00:00

Separate the op from the rq_flag_bits and have bcache
set/get the bio using bio_set_op_attrs/bio_op.

Signed-off-by: Mike Christie 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

bcache: use op_is_write instead of checking for REQ_WRITE

2016-06-07T19:41:38+00:00

We currently set REQ_WRITE/WRITE for all non READ IOs
like discard, flush, writesame, etc. In the next patches where we
no longer set up the op as a bitmap, we will not be able to
detect a operation direction like writesame by testing if REQ_WRITE is
set.

This has bcache use the op_is_write helper which will do the right
thing.

Signed-off-by: Mike Christie 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe