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authorJens Axboe <jens.axboe@oracle.com>2007-06-07 09:39:42 +0200
committerJens Axboe <jens.axboe@oracle.com>2007-06-08 08:34:11 +0200
commit620a324b744a7d66c3c45a83042f8e7fc9fc5a04 (patch)
tree07bf593206a2f38a28ba97811572d036c32b7927 /mm/mempolicy.c
parent475ecade683566b19ebb84972de864039ac5fce3 (diff)
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splice: __generic_file_splice_read: fix read/truncate race
Original patch and description from Neil Brown <neilb@suse.de>, merged and adapted to splice branch by me. Neils text follows: __generic_file_splice_read() currently samples the i_size at the start and doesn't do so again unless it needs to call ->readpage to load a page. After ->readpage it has to re-sample i_size as a truncate may have caused that page to be filled with zeros, and the read() call should not see these. However there are other activities that might cause ->readpage to be called on a page between the time that __generic_file_splice_read() samples i_size and when it finds that it has an uptodate page. These include at least read-ahead and possibly another thread performing a read So we must sample i_size *after* it has an uptodate page. Thus the current sampling at the start and after a read can be replaced with a sampling before page addition into spd. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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