linux-stable.git/drivers/md, branch v4.9.69

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: Fix building error on MIPS

2017-12-05T10:24:34+00:00

commit cf33c1ee5254c6a430bc1538232b49c3ea13e613 upstream.

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]

Signed-off-by: Huacai Chen 
Reviewed-by: Michael Lyle 
Signed-off-by: Michael Lyle 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

bcache: check ca->alloc_thread initialized before wake up it

2017-11-30T08:39:03+00:00

commit 91af8300d9c1d7c6b6a2fd754109e08d4798b8d8 upstream.

In bcache code, sysfs entries are created before all resources get
allocated, e.g. allocation thread of a cache set.

There is posibility for NULL pointer deference if a resource is accessed
but which is not initialized yet. Indeed Jorg Bornschein catches one on
cache set allocation thread and gets a kernel oops.

The reason for this bug is, when bch_bucket_alloc() is called during
cache set registration and attaching, ca->alloc_thread is not properly
allocated and initialized yet, call wake_up_process() on ca->alloc_thread
triggers NULL pointer deference failure. A simple and fast fix is, before
waking up ca->alloc_thread, checking whether it is allocated, and only
wake up ca->alloc_thread when it is not NULL.

Signed-off-by: Coly Li 
Reported-by: Jorg Bornschein 
Cc: Kent Overstreet 
Reviewed-by: Michael Lyle 
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

dm: fix race between dm_get_from_kobject() and __dm_destroy()

2017-11-30T08:39:02+00:00

commit b9a41d21dceadf8104812626ef85dc56ee8a60ed upstream.

The following BUG_ON was hit when testing repeat creation and removal of
DM devices:

    kernel BUG at drivers/md/dm.c:2919!
    CPU: 7 PID: 750 Comm: systemd-udevd Not tainted 4.1.44
    Call Trace:
     [] dm_get_from_kobject+0x34/0x3a
     [] dm_attr_show+0x2b/0x5e
     [] ? mutex_lock+0x26/0x44
     [] sysfs_kf_seq_show+0x83/0xcf
     [] kernfs_seq_show+0x23/0x25
     [] seq_read+0x16f/0x325
     [] kernfs_fop_read+0x3a/0x13f
     [] __vfs_read+0x26/0x9d
     [] ? security_file_permission+0x3c/0x44
     [] ? rw_verify_area+0x83/0xd9
     [] vfs_read+0x8f/0xcf
     [] ? __fdget_pos+0x12/0x41
     [] SyS_read+0x4b/0x76
     [] system_call_fastpath+0x12/0x71

The bug can be easily triggered, if an extra delay (e.g. 10ms) is added
between the test of DMF_FREEING & DMF_DELETING and dm_get() in
dm_get_from_kobject().

To fix it, we need to ensure the test of DMF_FREEING & DMF_DELETING and
dm_get() are done in an atomic way, so _minor_lock is used.

The other callers of dm_get() have also been checked to be OK: some
callers invoke dm_get() under _minor_lock, some callers invoke it under
_hash_lock, and dm_start_request() invoke it after increasing
md->open_count.

Signed-off-by: Hou Tao 
Signed-off-by: Mike Snitzer 
Signed-off-by: Greg Kroah-Hartman

dm: allocate struct mapped_device with kvzalloc

2017-11-30T08:39:02+00:00

commit 856eb0916d181da6d043cc33e03f54d5c5bbe54a upstream.

The structure srcu_struct can be very big, its size is proportional to the
value CONFIG_NR_CPUS. The Fedora kernel has CONFIG_NR_CPUS 8192, the field
io_barrier in the struct mapped_device has 84kB in the debugging kernel
and 50kB in the non-debugging kernel. The large size may result in failure
of the function kzalloc_node.

In order to avoid the allocation failure, we use the function
kvzalloc_node, this function falls back to vmalloc if a large contiguous
chunk of memory is not available. This patch also moves the field
io_barrier to the last position of struct mapped_device - the reason is
that on many processor architectures, short memory offsets result in
smaller code than long memory offsets - on x86-64 it reduces code size by
320 bytes.

Note to stable kernel maintainers - the kernels 4.11 and older don't have
the function kvzalloc_node, you can use the function vzalloc_node instead.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Greg Kroah-Hartman

dm bufio: fix integer overflow when limiting maximum cache size

2017-11-30T08:39:02+00:00

commit 74d4108d9e681dbbe4a2940ed8fdff1f6868184c upstream.

The default max_cache_size_bytes for dm-bufio is meant to be the lesser
of 25% of the size of the vmalloc area and 2% of the size of lowmem.
However, on 32-bit systems the intermediate result in the expression

    (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100

overflows, causing the wrong result to be computed.  For example, on a
32-bit system where the vmalloc area is 520093696 bytes, the result is
1174405 rather than the expected 130023424, which makes the maximum
cache size much too small (far less than 2% of lowmem).  This causes
severe performance problems for dm-verity users on affected systems.

Fix this by using mult_frac() to correctly multiply by a percentage.  Do
this for all places in dm-bufio that multiply by a percentage.  Also
replace (VMALLOC_END - VMALLOC_START) with VMALLOC_TOTAL, which contrary
to the comment is now defined in include/linux/vmalloc.h.

Depends-on: 9993bc635 ("sched/x86: Fix overflow in cyc2ns_offset")
Fixes: 95d402f057f2 ("dm: add bufio")
Signed-off-by: Eric Biggers 
Signed-off-by: Mike Snitzer 
Signed-off-by: Greg Kroah-Hartman

md/linear: shutup lockdep warnning

2017-10-21T15:21:35+00:00

[ Upstream commit d939cdfde34f50b95254b375f498447c82190b3e ]

Commit 03a9e24(md linear: fix a race between linear_add() and
linear_congested()) introduces the warnning.

Acked-by: Coly Li 
Signed-off-by: Shaohua Li 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

md/raid10: submit bio directly to replacement disk

2017-10-08T08:26:11+00:00

[ Upstream commit 6d399783e9d4e9bd44931501948059d24ad96ff8 ]

Commit 57c67df(md/raid10: submit IO from originating thread instead of
md thread) submits bio directly for normal disks but not for replacement
disks. There is no point we shouldn't do this for replacement disks.

Cc: NeilBrown 
Signed-off-by: Shaohua Li 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list

2017-10-05T07:43:59+00:00

commit 184a09eb9a2fe425e49c9538f1604b05ed33cfef upstream.

In release_stripe_plug(), if a stripe_head has its STRIPE_ON_UNPLUG_LIST
set, it indicates that this stripe_head is already in the raid5_plug_cb
list and release_stripe() would be called instead to drop a reference
count. Otherwise, the STRIPE_ON_UNPLUG_LIST bit would be set for this
stripe_head and it will get queued into the raid5_plug_cb list.

Since break_stripe_batch_list() did not preserve STRIPE_ON_UNPLUG_LIST,
A stripe could be re-added to plug list while it is still on that list
in the following situation. If stripe_head A is added to another
stripe_head B's batch list, in this case A will have its
batch_head != NULL and be added into the plug list. After that,
stripe_head B gets handled and called break_stripe_batch_list() to
reset all the batched stripe_head(including A which is still on
the plug list)'s state and reset their batch_head to NULL.
Before the plug list gets processed, if there is another write request
comes in and get stripe_head A, A will have its batch_head == NULL
(cleared by calling break_stripe_batch_list() on B) and be added to
plug list once again.

Signed-off-by: Dennis Yang 
Signed-off-by: Shaohua Li 
Signed-off-by: Greg Kroah-Hartman