• Jens Axboe's avatar
    blk-mq: fix corruption with direct issue · ffe81d45
    Jens Axboe authored
    If we attempt a direct issue to a SCSI device, and it returns BUSY, then
    we queue the request up normally. However, the SCSI layer may have
    already setup SG tables etc for this particular command. If we later
    merge with this request, then the old tables are no longer valid. Once
    we issue the IO, we only read/write the original part of the request,
    not the new state of it.
    
    This causes data corruption, and is most often noticed with the file
    system complaining about the just read data being invalid:
    
    [  235.934465] EXT4-fs error (device sda1): ext4_iget:4831: inode #7142: comm dpkg-query: bad extra_isize 24937 (inode size 256)
    
    because most of it is garbage...
    
    This doesn't happen from the normal issue path, as we will simply defer
    the request to the hardware queue dispatch list if we fail. Once it's on
    the dispatch list, we never merge with it.
    
    Fix this from the direct issue path by flagging the request as
    REQ_NOMERGE so we don't change the size of it before issue.
    
    See also:
      https://bugzilla.kernel.org/show_bug.cgi?id=201685Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
    Fixes: 6ce3dd6e ("blk-mq: issue directly if hw queue isn't busy in case of 'none'")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    ffe81d45
blk-mq.c 80.4 KB