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authorMartin Wilck <mwilck@suse.com>2018-07-25 23:15:09 +0200
committerJens Axboe <axboe@kernel.dk>2018-07-26 11:52:36 -0600
commit17d51b10d7773e4618bcac64648f30f12d4078fb (patch)
treec6b76e08ffb36ffac6e7e82047333316935bf0a4 /fs/block_dev.c
parent9362dd1109f87a9d0a798fbc890cb339c171ed35 (diff)
downloadlinux-stericsson-17d51b10d7773e4618bcac64648f30f12d4078fb.tar.gz
block: bio_iov_iter_get_pages: pin more pages for multi-segment IOs
bio_iov_iter_get_pages() currently only adds pages for the next non-zero segment from the iov_iter to the bio. That's suboptimal for callers, which typically try to pin as many pages as fit into the bio. This patch converts the current bio_iov_iter_get_pages() into a static helper, and introduces a new helper that allocates as many pages as 1) fit into the bio, 2) are present in the iov_iter, 3) and can be pinned by MM. Error is returned only if zero pages could be pinned. Because of 3), a zero return value doesn't necessarily mean all pages have been pinned. Callers that have to pin every page in the iov_iter must still call this function in a loop (this is currently the case). This change matters most for __blkdev_direct_IO_simple(), which calls bio_iov_iter_get_pages() only once. If it obtains less pages than requested, it returns a "short write" or "short read", and __generic_file_write_iter() falls back to buffered writes, which may lead to data corruption. Fixes: 72ecad22d9f1 ("block: support a full bio worth of IO for simplified bdev direct-io") Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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