linux-toradex.git/drivers/md/raid5.c, branch v4.10

md/r5cache: disable write back for degraded array

2017-01-24T19:26:06+00:00

write-back cache in degraded mode introduces corner cases to the array.
Although we try to cover all these corner cases, it is safer to just
disable write-back cache when the array is in degraded mode.

In this patch, we disable writeback cache for degraded mode:
1. On device failure, if the array enters degraded mode, raid5_error()
   will submit async job r5c_disable_writeback_async to disable
   writeback;
2. In r5c_journal_mode_store(), it is invalid to enable writeback in
   degraded mode;
3. In r5c_try_caching_write(), stripes with s->failed>0 will be handled
   in write-through mode.

Signed-off-by: Song Liu 
Signed-off-by: Shaohua Li

md/r5cache: shift complex rmw from read path to write path

2017-01-24T19:20:15+00:00

Write back cache requires a complex RMW mechanism, where old data is
read into dev->orig_page for prexor, and then xor is done with
dev->page. This logic is already implemented in the write path.

However, current read path is not awared of this requirement. When
the array is optimal, the RMW is not required, as the data are
read from raid disks. However, when the target stripe is degraded,
complex RMW is required to generate right data.

To keep read path as clean as possible, we handle read path by
flushing degraded, in-journal stripes before processing reads to
missing dev.

Specifically, when there is read requests to a degraded stripe
with data in journal, handle_stripe_fill() calls
r5c_make_stripe_write_out() and exits. Then handle_stripe_dirtying()
will do the complex RMW and flush the stripe to RAID disks. After
that, read requests are handled.

There is one more corner case when there is non-overwrite bio for
the missing (or out of sync) dev. handle_stripe_dirtying() will not
be able to process the non-overwrite bios without constructing the
data in handle_stripe_fill(). This is fixed by delaying non-overwrite
bios in handle_stripe_dirtying(). So handle_stripe_fill() works on
these bios after the stripe is flushed to raid disks.

Signed-off-by: Song Liu 
Signed-off-by: Shaohua Li

md/raid5: move comment of fetch_block to right location

2017-01-24T19:20:14+00:00

Signed-off-by: Song Liu 
Signed-off-by: Shaohua Li

md/r5cache: read data into orig_page for prexor of cached data

2017-01-24T19:20:14+00:00

With write back cache, we use orig_page to do prexor. This patch
makes sure we read data into orig_page for it.

Flag R5_OrigPageUPTDODATE is added to show whether orig_page
has the latest data from raid disk.

We introduce a helper function uptodate_for_rmw() to simplify
the a couple conditions in handle_stripe_dirtying().

Signed-off-by: Song Liu 
Signed-off-by: Shaohua Li

md/raid5: Use correct IS_ERR() variation on pointer check

2017-01-09T21:58:10+00:00

This fixes a build error on certain architectures, such as ppc64.

Fixes: 6995f0b247e("md: takeover should clear unrelated bits")
Signed-off-by: Jes Sorensen 
Signed-off-by: Shaohua Li

md: cleanup mddev flag clear for takeover

2017-01-05T19:45:18+00:00

Commit 6995f0b (md: takeover should clear unrelated bits) clear
unrelated bits, but it's quite fragile. To avoid error in the future,
define a macro for unsupported mddev flags for each raid type and use it
to clear unsupported mddev flags. This should be less error-prone.

Suggested-by: NeilBrown 
Signed-off-by: Shaohua Li

Merge branch 'md-next' into md-linus

2016-12-13T20:40:15+00:00

md: separate flags for superblock changes

2016-12-09T06:01:47+00:00

The mddev->flags are used for different purposes. There are a lot of
places we check/change the flags without masking unrelated flags, we
could check/change unrelated flags. These usage are most for superblock
write, so spearate superblock related flags. This should make the code
clearer and also fix real bugs.

Reviewed-by: NeilBrown 
Signed-off-by: Shaohua Li

md: takeover should clear unrelated bits

2016-12-09T06:00:11+00:00

When we change level from raid1 to raid5, the MD_FAILFAST_SUPPORTED bit
will be accidentally set, but raid5 doesn't support it. The same is true
for the MD_HAS_JOURNAL bit.

Fix: 46533ff (md: Use REQ_FAILFAST_* on metadata writes where appropriate)
Reviewed-by: NeilBrown 
Signed-off-by: Shaohua Li

md/raid5: limit request size according to implementation limits

2016-11-29T23:53:21+00:00

Current implementation employ 16bit counter of active stripes in lower
bits of bio->bi_phys_segments. If request is big enough to overflow
this counter bio will be completed and freed too early.

Fortunately this not happens in default configuration because several
other limits prevent that: stripe_cache_size * nr_disks effectively
limits count of active stripes. And small max_sectors_kb at lower
disks prevent that during normal read/write operations.

Overflow easily happens in discard if it's enabled by module parameter
"devices_handle_discard_safely" and stripe_cache_size is set big enough.

This patch limits requests size with 256Mb - 8Kb to prevent overflows.

Signed-off-by: Konstantin Khlebnikov 
Cc: Shaohua Li 
Cc: Neil Brown 
Cc: stable@vger.kernel.org
Signed-off-by: Shaohua Li