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Ilya Dryomov
6ac56951dc
Commit93c1defedc("rbd: remove the discard_zeroes_data flag") explicitly didn't implement REQ_OP_WRITE_ZEROES for rbd, while the following commit48920ff2a5("block: remove the discard_zeroes_data flag") dropped ->discard_zeroes_data in favor of REQ_OP_WRITE_ZEROES. rbd does support efficient zeroing via CEPH_OSD_OP_ZERO opcode and will release either some or all blocks depending on whether the zeroing request is rbd_obj_bytes() aligned. This is how we currently implement discards, so REQ_OP_WRITE_ZEROES can be identical to REQ_OP_DISCARD for now. Caveats: - REQ_NOUNMAP is ignored, but AFAICT that's true of at least two other current implementations - nvme and loop - there is no ->write_zeroes_alignment and blk_bio_write_zeroes_split() is hence less helpful than blk_bio_discard_split(), but this can (and should) be fixed on the rbd side In the future we will split these into two code paths to respect REQ_NOUNMAP on zeroout and save on zeroing blocks that couldn't be released on discard. Fixes:93c1defedc("rbd: remove the discard_zeroes_data flag") Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Jason Dillaman <dillaman@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.