linux-toradex.git/drivers/md/bcache/io.c, branch v4.8-rc8

block: simplify and cleanup bvec pool handling

2016-07-20T23:37:02+00:00

Instead of a flag and an index just make sure an index of 0 means
no need to free the bvec array.  Also move the constants related
to the bvec pools together and use a consistent naming scheme for
them.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Johannes Thumshirn 
Reviewed-by: Mike Christie 
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

bcache: remove driver private bio splitting code

2015-08-13T18:31:40+00:00

The bcache driver has always accepted arbitrarily large bios and split
them internally.  Now that every driver must accept arbitrarily large
bios this code isn't nessecary anymore.

Cc: linux-bcache@vger.kernel.org
Signed-off-by: Kent Overstreet 
[dpark: add more description in commit message]
Signed-off-by: Dongsu Park 
Signed-off-by: Ming Lin 
Signed-off-by: Jens Axboe

block: add a bi_error field to struct bio

2015-07-29T14:55:15+00:00

Currently we have two different ways to signal an I/O error on a BIO:

 (1) by clearing the BIO_UPTODATE flag
 (2) by returning a Linux errno value to the bi_end_io callback

The first one has the drawback of only communicating a single possible
error (-EIO), and the second one has the drawback of not beeing persistent
when bios are queued up, and are not passed along from child to parent
bio in the ever more popular chaining scenario.  Having both mechanisms
available has the additional drawback of utterly confusing driver authors
and introducing bugs where various I/O submitters only deal with one of
them, and the others have to add boilerplate code to deal with both kinds
of error returns.

So add a new bi_error field to store an errno value directly in struct
bio and remove the existing mechanisms to clean all this up.

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

bcache: don't embed 'return' statements in closure macros

2015-07-11T15:57:32+00:00

This is horribly confusing, it breaks the flow of the code without
it being apparent in the caller.

Signed-off-by: Jens Axboe 
Acked-by: Christoph Hellwig

block: remove management of bi_remaining when restoring original bi_end_io

2015-05-22T14:58:55+00:00

Commit c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for
non-chains") regressed all existing callers that followed this pattern:
 1) saving a bio's original bi_end_io
 2) wiring up an intermediate bi_end_io
 3) restoring the original bi_end_io from intermediate bi_end_io
 4) calling bio_endio() to execute the restored original bi_end_io

The regression was due to BIO_CHAIN only ever getting set if
bio_inc_remaining() is called.  For the above pattern it isn't set until
step 3 above (step 2 would've needed to establish BIO_CHAIN).  As such
the first bio_endio(), in step 2 above, never decremented __bi_remaining
before calling the intermediate bi_end_io -- leaving __bi_remaining with
the value 1 instead of 0.  When bio_inc_remaining() occurred during step
3 it brought it to a value of 2.  When the second bio_endio() was
called, in step 4 above, it should've called the original bi_end_io but
it didn't because there was an extra reference that wasn't dropped (due
to atomic operations being optimized away since BIO_CHAIN wasn't set
upfront).

Fix this issue by removing the __bi_remaining management complexity for
all callers that use the above pattern -- bio_chain() is the only
interface that _needs_ to be concerned with __bi_remaining.  For the
above pattern callers just expect the bi_end_io they set to get called!
Remove bio_endio_nodec() and also remove all bio_inc_remaining() calls
that aren't associated with the bio_chain() interface.

Also, the bio_inc_remaining() interface has been moved local to bio.c.

Fixes: c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for non-chains")
Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Mike Snitzer 
Signed-off-by: Jens Axboe

block: Introduce new bio_split()

2013-11-24T06:33:57+00:00

The new bio_split() can split arbitrary bios - it's not restricted to
single page bios, like the old bio_split() (previously renamed to
bio_pair_split()). It also has different semantics - it doesn't allocate
a struct bio_pair, leaving it up to the caller to handle completions.

Then convert the existing bio_pair_split() users to the new bio_split()
- and also nvme, which was open coding bio splitting.

(We have to take that BUG_ON() out of bio_integrity_trim() because this
bio_split() needs to use it, and there's no reason it has to be used on
bios marked as cloned; BIO_CLONED doesn't seem to have clearly
documented semantics anyways.)

Signed-off-by: Kent Overstreet 
Cc: Jens Axboe 
Cc: Martin K. Petersen 
Cc: Matthew Wilcox 
Cc: Keith Busch 
Cc: Vishal Verma 
Cc: Jiri Kosina 
Cc: Neil Brown

block: Generic bio chaining

2013-11-24T06:33:56+00:00

This adds a generic mechanism for chaining bio completions. This is
going to be used for a bio_split() replacement, and it turns out to be
very useful in a fair amount of driver code - a fair number of drivers
were implementing this in their own roundabout ways, often painfully.

Note that this means it's no longer to call bio_endio() more than once
on the same bio! This can cause problems for drivers that save/restore
bi_end_io. Arguably they shouldn't be saving/restoring bi_end_io at all
- in all but the simplest cases they'd be better off just cloning the
bio, and immutable biovecs is making bio cloning cheaper. But for now,
we add a bio_endio_nodec() for these cases.

Signed-off-by: Kent Overstreet 
Cc: Jens Axboe

block: Remove bi_idx hacks

2013-11-24T06:33:55+00:00

Now that drivers have been converted to the new bvec_iter primitives,
there's no need to trim the bvec before we submit it; and we can't trim
it once we start sharing bvecs.

It used to be that passing a partially completed bio (i.e. one with
nonzero bi_idx) to generic_make_request() was a dangerous thing -
various drivers would choke on such things. But with immutable biovecs
and our new bio splitting that shares the biovecs, submitting partially
completed bios has to work (and should work, now that all the drivers
have been completed to the new primitives)

Signed-off-by: Kent Overstreet 
Cc: Jens Axboe

block: Kill bio_segments()/bi_vcnt usage

2013-11-24T06:33:51+00:00

When we start sharing biovecs, keeping bi_vcnt accurate for splits is
going to be error prone - and unnecessary, if we refactor some code.

So bio_segments() has to go - but most of the existing users just needed
to know if the bio had multiple segments, which is easier - add a
bio_multiple_segments() for them.

(Two of the current uses of bio_segments() are going to go away in a
couple patches, but the current implementation of bio_segments() is
unsafe as soon as we start doing driver conversions for immutable
biovecs - so implement a dumb version for bisectability, it'll go away
in a couple patches)

Signed-off-by: Kent Overstreet 
Cc: Jens Axboe 
Cc: Neil Brown 
Cc: Nagalakshmi Nandigama 
Cc: Sreekanth Reddy 
Cc: "James E.J. Bottomley"