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17 May 2024, 09:02:56 UTC
Revision c15227de132f1295f3db6b7df9079956b1020fd8 authored by Christoph Hellwig on 30 September 2009, 11:52:12 UTC, committed by Jens Axboe on 01 October 2009, 19:19:30 UTC 
block: use normal I/O path for discard requests
 
prepare_discard_fn() was being called in a place where memory allocation
was effectively impossible.  This makes it inappropriate for all but
the most trivial translations of Linux's DISCARD operation to the block
command set.  Additionally adding a payload there makes the ownership
of the bio backing unclear as it's now allocated by the device driver
and not the submitter as usual.

It is replaced with QUEUE_FLAG_DISCARD which is used to indicate whether
the queue supports discard operations or not.  blkdev_issue_discard now
allocates a one-page, sector-length payload which is the right thing
for the common ATA and SCSI implementations.

The mtd implementation of prepare_discard_fn() is replaced with simply
checking for the request being a discard.

Largely based on a previous patch from Matthew Wilcox <matthew@wil.cx>
which did the prepare_discard_fn but not the different payload allocation
yet.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
1 parent 3bd0f0c
History
Tip revision: c15227de132f1295f3db6b7df9079956b1020fd8 authored by Christoph Hellwig on 30 September 2009, 11:52:12 UTC
block: use normal I/O path for discard requests
Tip revision: c15227d
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