bcache: update min_heap_callbacks to use default builtin swap

Replace the swp function pointer in the min_heap_callbacks of bcache with
NULL, allowing direct usage of the default builtin swap implem

bcache: update min_heap_callbacks to use default builtin swap

Replace the swp function pointer in the min_heap_callbacks of bcache with
NULL, allowing direct usage of the default builtin swap implementation.
This modification simplifies the code and improves performance by removing
unnecessary function indirection.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kuan-Wei Chiu <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Ching-Chun (Jim) Huang <[email protected]>
Cc: Coly Li <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: "Liang, Kan" <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Sakai <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

show more ...

bcache: remove heap-related macros and switch to generic min_heap

Drop the heap-related macros from bcache and replacing them with the
generic min_heap implementation from include/linux. By doing s

bcache: remove heap-related macros and switch to generic min_heap

Drop the heap-related macros from bcache and replacing them with the
generic min_heap implementation from include/linux. By doing so, code
readability is improved by using functions instead of macros. Moreover,
the min_heap implementation in include/linux adopts a bottom-up variation
compared to the textbook version currently used in bcache. This bottom-up
variation allows for approximately 50% reduction in the number of
comparison operations during heap siftdown, without changing the number of
swaps, thus making it more efficient.

Link: https://lkml.kernel.org/ioyfizrzq7w7mjrqcadtzsfgpuntowtjdw5pgn4qhvsdp4mqqg@nrlek5vmisbu
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kuan-Wei Chiu <[email protected]>
Reviewed-by: Ian Rogers <[email protected]>
Acked-by: Coly Li <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Bagas Sanjaya <[email protected]>
Cc: Brian Foster <[email protected]>
Cc: Ching-Chun (Jim) Huang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Sakai <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Randy Dunlap <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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bcache: code cleanup in __bch_bucket_alloc_set()

In __bch_bucket_alloc_set() the lines after lable 'err:' indeed do
nothing useful after multiple cache devices are removed from bcache
code. This cle

bcache: code cleanup in __bch_bucket_alloc_set()

In __bch_bucket_alloc_set() the lines after lable 'err:' indeed do
nothing useful after multiple cache devices are removed from bcache
code. This cleanup patch drops the useless code to save a bit CPU
cycles.

Signed-off-by: Coly Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: allow allocator to invalidate bucket in gc

Currently, if the gc is running, when the allocator found free_inc
is empty, allocator has to wait the gc finish. Before that, the
IO is blocked.

bcache: allow allocator to invalidate bucket in gc

Currently, if the gc is running, when the allocator found free_inc
is empty, allocator has to wait the gc finish. Before that, the
IO is blocked.

But actually, there would be some buckets is reclaimable before gc,
and gc will never mark this kind of bucket to be unreclaimable.

So we can put these buckets into free_inc in gc running to avoid
IO being blocked.

Signed-off-by: Dongsheng Yang <[email protected]>
Signed-off-by: Mingzhe Zou <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

show more ...

block: decouple REQ_OP_SECURE_ERASE from REQ_OP_DISCARD

Secure erase is a very different operation from discard in that it is
a data integrity operation vs hint. Fully split the limits and helper
i

block: decouple REQ_OP_SECURE_ERASE from REQ_OP_DISCARD

Secure erase is a very different operation from discard in that it is
a data integrity operation vs hint. Fully split the limits and helper
infrastructure to make the separation more clear.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Acked-by: Christoph Böhmwalder <[email protected]> [drbd]
Acked-by: Ryusuke Konishi <[email protected]> [nifs2]
Acked-by: Jaegeuk Kim <[email protected]> [f2fs]
Acked-by: Coly Li <[email protected]> [bcache]
Acked-by: David Sterba <[email protected]> [btrfs]
Acked-by: Chao Yu <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: remove PTR_CACHE

Remove the PTR_CACHE inline and replace it with a direct dereference
of c->cache.

(Coly Li: fix the typo from PTR_BUCKET to PTR_CACHE in commit log)

Signed-off-by: Christo

bcache: remove PTR_CACHE

Remove the PTR_CACHE inline and replace it with a direct dereference
of c->cache.

(Coly Li: fix the typo from PTR_BUCKET to PTR_CACHE in commit log)

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: remove embedded struct cache_sb from struct cache_set

Since bcache code was merged into mainline kerrnel, each cache set only
as one single cache in it. The multiple caches framework is here

bcache: remove embedded struct cache_sb from struct cache_set

Since bcache code was merged into mainline kerrnel, each cache set only
as one single cache in it. The multiple caches framework is here but the
code is far from completed. Considering the multiple copies of cached
data can also be stored on e.g. md raid1 devices, it is unnecessary to
support multiple caches in one cache set indeed.

The previous preparation patches fix the dependencies of explicitly
making a cache set only have single cache. Now we don't have to maintain
an embedded partial super block in struct cache_set, the in-memory super
block can be directly referenced from struct cache.

This patch removes the embedded struct cache_sb from struct cache_set,
and fixes all locations where the superb lock was referenced from this
removed super block by referencing the in-memory super block of struct
cache.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: check and set sync status on cache's in-memory super block

Currently the cache's sync status is checked and set on cache set's in-
memory partial super block. After removing the embedded str

bcache: check and set sync status on cache's in-memory super block

Currently the cache's sync status is checked and set on cache set's in-
memory partial super block. After removing the embedded struct cache_sb
from cache set and reference cache's in-memory super block from struct
cache_set, the sync status can set and check directly on cache's super
block.

This patch checks and sets the cache sync status directly on cache's
in-memory super block. This is a preparation for later removing embedded
struct cache_sb from struct cache_set.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: remove for_each_cache()

Since now each cache_set explicitly has single cache, for_each_cache()
is unnecessary. This patch removes this macro, and update all locations
where it is used, and m

bcache: remove for_each_cache()

Since now each cache_set explicitly has single cache, for_each_cache()
is unnecessary. This patch removes this macro, and update all locations
where it is used, and makes sure all code logic still being consistent.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: explicitly make cache_set only have single cache

Currently although the bcache code has a framework for multiple caches
in a cache set, but indeed the multiple caches never completed and use

bcache: explicitly make cache_set only have single cache

Currently although the bcache code has a framework for multiple caches
in a cache set, but indeed the multiple caches never completed and users
use md raid1 for multiple copies of the cached data.

This patch does the following change in struct cache_set, to explicitly
make a cache_set only have single cache,
- Change pointer array "*cache[MAX_CACHES_PER_SET]" to a single pointer
"*cache".
- Remove pointer array "*cache_by_alloc[MAX_CACHES_PER_SET]".
- Remove "caches_loaded".

Now the code looks as exactly what it does in practic: only one cache is
used in the cache set.

Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: remove 'int n' from parameter list of bch_bucket_alloc_set()

The parameter 'int n' from bch_bucket_alloc_set() is not cleared
defined. From the code comments n is the number of buckets to al

bcache: remove 'int n' from parameter list of bch_bucket_alloc_set()

The parameter 'int n' from bch_bucket_alloc_set() is not cleared
defined. From the code comments n is the number of buckets to alloc, but
from the code itself 'n' is the maximum cache to iterate. Indeed all the
locations where bch_bucket_alloc_set() is called, 'n' is alwasy 1.

This patch removes the confused and unnecessary 'int n' from parameter
list of bch_bucket_alloc_set(), and explicitly allocates only 1 bucket
for its caller.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: add bucket_size_hi into struct cache_sb_disk for large bucket

The large bucket feature is to extend bucket_size from 16bit to 32bit.

When create cache device on zoned device (e.g. zoned NVM

bcache: add bucket_size_hi into struct cache_sb_disk for large bucket

The large bucket feature is to extend bucket_size from 16bit to 32bit.

When create cache device on zoned device (e.g. zoned NVMe SSD), making
a single bucket cover one or more zones of the zoned device is the
simplest way to support zoned device as cache by bcache.

But current maximum bucket size is 16MB and a typical zone size of zoned
device is 256MB, this is the major motiviation to extend bucket size to
a larger bit width.

This patch is the basic and first change to support large bucket size,
the major changes it makes are,
- Add BCH_FEATURE_INCOMPAT_LARGE_BUCKET for the large bucket feature,
INCOMPAT means it introduces incompatible on-disk format change.
- Add BCH_FEATURE_INCOMPAT_FUNCS(large_bucket, LARGE_BUCKET) routines.
- Adds __le16 bucket_size_hi into struct cache_sb_disk at offset 0x8d0
for the on-disk super block format.
- For the in-memory super block struct cache_sb, member bucket_size is
extended from __u16 to __32.
- Add get_bucket_size() to combine the bucket_size and bucket_size_hi
from struct cache_sb_disk into an unsigned int value.

Since we already have large bucket size helpers meta_bucket_pages(),
meta_bucket_bytes() and alloc_meta_bucket_pages(), they make sure when
bucket size > 8MB, the memory allocation for bcache meta data bucket
won't fail no matter how large the bucket size extended. So these meta
data buckets are handled properly when the bucket size width increase
from 16bit to 32bit, we don't need to worry about them.

Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

Revert "bcache: ignore pending signals when creating gc and allocator thread"

This reverts commit 0b96da639a4874311e9b5156405f69ef9fc3bef8.

We can't just go flushing random signals, under the assum

Revert "bcache: ignore pending signals when creating gc and allocator thread"

This reverts commit 0b96da639a4874311e9b5156405f69ef9fc3bef8.

We can't just go flushing random signals, under the assumption that the
OOM killer will just do something else. It's not safe from the OOM
perspective, and it could also cause other signals to get randomly lost.

Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: ignore pending signals when creating gc and allocator thread

When run a cache set, all the bcache btree node of this cache set will
be checked by bch_btree_check(). If the bcache btree is ve

bcache: ignore pending signals when creating gc and allocator thread

When run a cache set, all the bcache btree node of this cache set will
be checked by bch_btree_check(). If the bcache btree is very large,
iterating all the btree nodes will occupy too much system memory and
the bcache registering process might be selected and killed by system
OOM killer. kthread_run() will fail if current process has pending
signal, therefore the kthread creating in run_cache_set() for gc and
allocator kernel threads are very probably failed for a very large
bcache btree.

Indeed such OOM is safe and the registering process will exit after
the registration done. Therefore this patch flushes pending signals
during the cache set start up, specificly in bch_cache_allocator_start()
and bch_gc_thread_start(), to make sure run_cache_set() won't fail for
large cahced data set.

Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: fix deadlock in bcache_allocator

bcache_allocator can call the following:

bch_allocator_thread()
-> bch_prio_write()
-> bch_bucket_alloc()
-> wait on &ca->set->bucket_wait

bcache: fix deadlock in bcache_allocator

bcache_allocator can call the following:

bch_allocator_thread()
-> bch_prio_write()
-> bch_bucket_alloc()
-> wait on &ca->set->bucket_wait

But the wake up event on bucket_wait is supposed to come from
bch_allocator_thread() itself => deadlock:

[ 1158.490744] INFO: task bcache_allocato:15861 blocked for more than 10 seconds.
[ 1158.495929] Not tainted 5.3.0-050300rc3-generic #201908042232
[ 1158.500653] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1158.504413] bcache_allocato D 0 15861 2 0x80004000
[ 1158.504419] Call Trace:
[ 1158.504429] __schedule+0x2a8/0x670
[ 1158.504432] schedule+0x2d/0x90
[ 1158.504448] bch_bucket_alloc+0xe5/0x370 [bcache]
[ 1158.504453] ? wait_woken+0x80/0x80
[ 1158.504466] bch_prio_write+0x1dc/0x390 [bcache]
[ 1158.504476] bch_allocator_thread+0x233/0x490 [bcache]
[ 1158.504491] kthread+0x121/0x140
[ 1158.504503] ? invalidate_buckets+0x890/0x890 [bcache]
[ 1158.504506] ? kthread_park+0xb0/0xb0
[ 1158.504510] ret_from_fork+0x35/0x40

Fix by making the call to bch_prio_write() non-blocking, so that
bch_allocator_thread() never waits on itself.

Moreover, make sure to wake up the garbage collector thread when
bch_prio_write() is failing to allocate buckets.

BugLink: https://bugs.launchpad.net/bugs/1784665
BugLink: https://bugs.launchpad.net/bugs/1796292
Signed-off-by: Andrea Righi <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: check CACHE_SET_IO_DISABLE in allocator code

If CACHE_SET_IO_DISABLE of a cache set flag is set by too many I/O
errors, currently allocator routines can still continue allocate
space which m

bcache: check CACHE_SET_IO_DISABLE in allocator code

If CACHE_SET_IO_DISABLE of a cache set flag is set by too many I/O
errors, currently allocator routines can still continue allocate
space which may introduce inconsistent metadata state.

This patch checkes CACHE_SET_IO_DISABLE bit in following allocator
routines,
- bch_bucket_alloc()
- __bch_bucket_alloc_set()
Once CACHE_SET_IO_DISABLE is set on cache set, the allocator routines
may reject allocation request earlier to avoid potential inconsistent
metadata.

Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: avoid clang -Wunintialized warning

clang has identified a code path in which it thinks a
variable may be unused:

drivers/md/bcache/alloc.c:333:4: error: variable 'bucket' is used uninitiali

bcache: avoid clang -Wunintialized warning

clang has identified a code path in which it thinks a
variable may be unused:

drivers/md/bcache/alloc.c:333:4: error: variable 'bucket' is used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
fifo_pop(&ca->free_inc, bucket);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop'
#define fifo_pop(fifo, i) fifo_pop_front(fifo, (i))
^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/md/bcache/util.h:189:6: note: expanded from macro 'fifo_pop_front'
if (_r) { \
^~
drivers/md/bcache/alloc.c:343:46: note: uninitialized use occurs here
allocator_wait(ca, bch_allocator_push(ca, bucket));
^~~~~~
drivers/md/bcache/alloc.c:287:7: note: expanded from macro 'allocator_wait'
if (cond) \
^~~~
drivers/md/bcache/alloc.c:333:4: note: remove the 'if' if its condition is always true
fifo_pop(&ca->free_inc, bucket);
^
drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop'
#define fifo_pop(fifo, i) fifo_pop_front(fifo, (i))
^
drivers/md/bcache/util.h:189:2: note: expanded from macro 'fifo_pop_front'
if (_r) { \
^
drivers/md/bcache/alloc.c:331:15: note: initialize the variable 'bucket' to silence this warning
long bucket;
^

This cannot happen in practice because we only enter the loop
if there is at least one element in the list.

Slightly rearranging the code makes this clearer to both the
reader and the compiler, which avoids the warning.

Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: use MAX_CACHES_PER_SET instead of magic number 8 in __bch_bucket_alloc_set

Current cache_set has MAX_CACHES_PER_SET caches most, and the macro
is used for
"
struct cache *cache_by_alloc[MAX

bcache: use MAX_CACHES_PER_SET instead of magic number 8 in __bch_bucket_alloc_set

Current cache_set has MAX_CACHES_PER_SET caches most, and the macro
is used for
"
struct cache *cache_by_alloc[MAX_CACHES_PER_SET];
"
in the define of struct cache_set.

Use MAX_CACHES_PER_SET instead of magic number 8 in
__bch_bucket_alloc_set.

Signed-off-by: Shenghui Wang <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: style fix to add a blank line after declarations

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Shenghui Wang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

bcache: style fix to replace 'unsigned' by 'unsigned int'

This patch fixes warning reported by checkpatch.pl by replacing 'unsigned'
with 'unsigned int'.

Signed-off-by: Coly Li <[email protected]>
Rev

bcache: style fix to replace 'unsigned' by 'unsigned int'

This patch fixes warning reported by checkpatch.pl by replacing 'unsigned'
with 'unsigned int'.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Shenghui Wang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: add wait_for_kthread_stop() in bch_allocator_thread()

When CACHE_SET_IO_DISABLE is set on cache set flags, bcache allocator
thread routine bch_allocator_thread() may stop the while-loops and

bcache: add wait_for_kthread_stop() in bch_allocator_thread()

When CACHE_SET_IO_DISABLE is set on cache set flags, bcache allocator
thread routine bch_allocator_thread() may stop the while-loops and
exit. Then it is possible to observe the following kernel oops message,

[ 631.068366] bcache: bch_btree_insert() error -5
[ 631.069115] bcache: cached_dev_detach_finish() Caching disabled for sdf
[ 631.070220] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[ 631.070250] PGD 0 P4D 0
[ 631.070261] Oops: 0002 [#1] SMP PTI
[snipped]
[ 631.070578] Workqueue: events cache_set_flush [bcache]
[ 631.070597] RIP: 0010:exit_creds+0x1b/0x50
[ 631.070610] RSP: 0018:ffffc9000705fe08 EFLAGS: 00010246
[ 631.070626] RAX: 0000000000000001 RBX: ffff880a622ad300 RCX: 000000000000000b
[ 631.070645] RDX: 0000000000000601 RSI: 000000000000000c RDI: 0000000000000000
[ 631.070663] RBP: ffff880a622ad300 R08: ffffea00190c66e0 R09: 0000000000000200
[ 631.070682] R10: ffff880a48123000 R11: ffff880000000000 R12: 0000000000000000
[ 631.070700] R13: ffff880a4b160e40 R14: ffff880a4b160000 R15: 0ffff880667e2530
[ 631.070719] FS: 0000000000000000(0000) GS:ffff880667e00000(0000) knlGS:0000000000000000
[ 631.070740] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 631.070755] CR2: 0000000000000000 CR3: 000000000200a001 CR4: 00000000003606e0
[ 631.070774] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 631.070793] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 631.070811] Call Trace:
[ 631.070828] __put_task_struct+0x55/0x160
[ 631.070845] kthread_stop+0xee/0x100
[ 631.070863] cache_set_flush+0x11d/0x1a0 [bcache]
[ 631.070879] process_one_work+0x146/0x340
[ 631.070892] worker_thread+0x47/0x3e0
[ 631.070906] kthread+0xf5/0x130
[ 631.070917] ? max_active_store+0x60/0x60
[ 631.070930] ? kthread_bind+0x10/0x10
[ 631.070945] ret_from_fork+0x35/0x40
[snipped]
[ 631.071017] RIP: exit_creds+0x1b/0x50 RSP: ffffc9000705fe08
[ 631.071033] CR2: 0000000000000000
[ 631.071045] ---[ end trace 011c63a24b22c927 ]---
[ 631.071085] bcache: bcache_device_free() bcache0 stopped

The reason is when cache_set_flush() tries to call kthread_stop() to stop
allocator thread, but it exits already due to cache device I/O errors.

This patch adds wait_for_kthread_stop() at tail of bch_allocator_thread(),
to prevent the thread routine exiting directly. Then the allocator thread
can be blocked at wait_for_kthread_stop() and wait for cache_set_flush()
to stop it by calling kthread_stop().

changelog:
v3: add Reviewed-by from Hannnes.
v2: not directly return from allocator_wait(), move 'return 0' to tail of
bch_allocator_thread().
v1: initial version.

Fixes: 771f393e8ffc ("bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags")
Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags

When too many I/Os failed on cache device, bch_cache_set_error() is called
in the error handling code path to retire whole problematic cach

bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags

When too many I/Os failed on cache device, bch_cache_set_error() is called
in the error handling code path to retire whole problematic cache set. If
new I/O requests continue to come and take refcount dc->count, the cache
set won't be retired immediately, this is a problem.

Further more, there are several kernel thread and self-armed kernel work
may still running after bch_cache_set_error() is called. It needs to wait
quite a while for them to stop, or they won't stop at all. They also
prevent the cache set from being retired.

The solution in this patch is, to add per cache set flag to disable I/O
request on this cache and all attached backing devices. Then new coming I/O
requests can be rejected in *_make_request() before taking refcount, kernel
threads and self-armed kernel worker can stop very fast when flags bit
CACHE_SET_IO_DISABLE is set.

Because bcache also do internal I/Os for writeback, garbage collection,
bucket allocation, journaling, this kind of I/O should be disabled after
bch_cache_set_error() is called. So closure_bio_submit() is modified to
check whether CACHE_SET_IO_DISABLE is set on cache_set->flags. If set,
closure_bio_submit() will set bio->bi_status to BLK_STS_IOERR and
return, generic_make_request() won't be called.

A sysfs interface is also added to set or clear CACHE_SET_IO_DISABLE bit
from cache_set->flags, to disable or enable cache set I/O for debugging. It
is helpful to trigger more corner case issues for failed cache device.

Changelog
v4, add wait_for_kthread_stop(), and call it before exits writeback and gc
kernel threads.
v3, change CACHE_SET_IO_DISABLE from 4 to 3, since it is bit index.
remove "bcache: " prefix when printing out kernel message.
v2, more changes by previous review,
- Use CACHE_SET_IO_DISABLE of cache_set->flags, suggested by Junhui.
- Check CACHE_SET_IO_DISABLE in bch_btree_gc() to stop a while-loop, this
is reported and inspired from origal patch of Pavel Vazharov.
v1, initial version.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Cc: Junhui Tang <[email protected]>
Cc: Michael Lyle <[email protected]>
Cc: Pavel Vazharov <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

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bcache: properly set task state in bch_writeback_thread()

Kernel thread routine bch_writeback_thread() has the following code block,

447 down_write(&dc->writeback_lock);
448~450 if (che

bcache: properly set task state in bch_writeback_thread()

Kernel thread routine bch_writeback_thread() has the following code block,

447 down_write(&dc->writeback_lock);
448~450 if (check conditions) {
451 up_write(&dc->writeback_lock);
452 set_current_state(TASK_INTERRUPTIBLE);
453
454 if (kthread_should_stop())
455 return 0;
456
457 schedule();
458 continue;
459 }

If condition check is true, its task state is set to TASK_INTERRUPTIBLE
and call schedule() to wait for others to wake up it.

There are 2 issues in current code,
1, Task state is set to TASK_INTERRUPTIBLE after the condition checks, if
another process changes the condition and call wake_up_process(dc->
writeback_thread), then at line 452 task state is set back to
TASK_INTERRUPTIBLE, the writeback kernel thread will lose a chance to be
waken up.
2, At line 454 if kthread_should_stop() is true, writeback kernel thread
will return to kernel/kthread.c:kthread() with TASK_INTERRUPTIBLE and
call do_exit(). It is not good to enter do_exit() with task state
TASK_INTERRUPTIBLE, in following code path might_sleep() is called and a
warning message is reported by __might_sleep(): "WARNING: do not call
blocking ops when !TASK_RUNNING; state=1 set at [xxxx]".

For the first issue, task state should be set before condition checks.
Ineed because dc->writeback_lock is required when modifying all the
conditions, calling set_current_state() inside code block where dc->
writeback_lock is hold is safe. But this is quite implicit, so I still move
set_current_state() before all the condition checks.

For the second issue, frankley speaking it does not hurt when kernel thread
exits with TASK_INTERRUPTIBLE state, but this warning message scares users,
makes them feel there might be something risky with bcache and hurt their
data. Setting task state to TASK_RUNNING before returning fixes this
problem.

In alloc.c:allocator_wait(), there is also a similar issue, and is also
fixed in this patch.

Changelog:
v3: merge two similar fixes into one patch
v2: fix the race issue in v1 patch.
v1: initial buggy fix.

Signed-off-by: Coly Li <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Cc: Michael Lyle <[email protected]>
Cc: Junhui Tang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

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bcache: segregate flash only volume write streams

In such scenario that there are some flash only volumes
, and some cached devices, when many tasks request these devices in
writeback mode, the writ

bcache: segregate flash only volume write streams

In such scenario that there are some flash only volumes
, and some cached devices, when many tasks request these devices in
writeback mode, the write IOs may fall to the same bucket as bellow:
| cached data | flash data | cached data | cached data| flash data|
then after writeback of these cached devices, the bucket would
be like bellow bucket:
| free | flash data | free | free | flash data |

So, there are many free space in this bucket, but since data of flash
only volumes still exists, so this bucket cannot be reclaimable,
which would cause waste of bucket space.

In this patch, we segregate flash only volume write streams from
cached devices, so data from flash only volumes and cached devices
can store in different buckets.

Compare to v1 patch, this patch do not add a additionally open bucket
list, and it is try best to segregate flash only volume write streams
from cached devices, sectors of flash only volumes may still be mixed
with dirty sectors of cached device, but the number is very small.

[mlyle: fixed commit log formatting, permissions, line endings]

Signed-off-by: Tang Junhui <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Signed-off-by: Michael Lyle <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

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bcache: Fix building error on MIPS

This patch try to fix the building error on MIPS. The reason is MIPS
has already defined the PTR macro, which conflicts with the PTR macro
in include/uapi/linux/bc

bcache: Fix building error on MIPS

This patch try to fix the building error on MIPS. The reason is MIPS
has already defined the PTR macro, which conflicts with the PTR macro
in include/uapi/linux/bcache.h.

[fixed by mlyle: corrected a line-length issue]

Cc: [email protected]
Signed-off-by: Huacai Chen <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Signed-off-by: Michael Lyle <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...