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authorChristoph Hellwig <hch@infradead.org>2011-10-17 12:57:20 +0200
committerJens Axboe <axboe@kernel.dk>2011-10-17 12:57:20 +0200
commit456be1484ffc72a24bdb4200b5847c4fa90139d9 (patch)
tree570f0818bd6cfa245ab23d0121853b7b1e5a649b /Documentation/networking/x25.txt
parent8bc03e8f3a334e09e89a7dffb486ee97a5ce84ae (diff)
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loop: remove the incorrect write_begin/write_end shortcut
Currently the loop device tries to call directly into write_begin/write_end instead of going through ->write if it can. This is a fairly nasty shortcut as write_begin and write_end are only callbacks for the generic write code and expect to be called with filesystem specific locks held. This code currently causes various issues for clustered filesystems as it doesn't take the required cluster locks, and it also causes issues for XFS as it doesn't properly lock against the swapext ioctl as called by the defragmentation tools. This in case causes data corruption if defragmentation hits a busy loop device in the wrong time window, as reported by RH QA. The reason why we have this shortcut is that it saves a data copy when doing a transformation on the loop device, which is the technical term for using cryptoloop (or an XOR transformation). Given that cryptoloop has been deprecated in favour of dm-crypt my opinion is that we should simply drop this shortcut instead of finding complicated ways to to introduce a formal interface for this shortcut. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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