• Jens Axboe's avatar
    block: provide bio_uninit() free freeing integrity/task associations · 9ae3b3f5
    Jens Axboe authored
    Wen reports significant memory leaks with DIF and O_DIRECT:
    
    "With nvme devive + T10 enabled, On a system it has 256GB and started
    logging /proc/meminfo & /proc/slabinfo for every minute and in an hour
    it increased by 15968128 kB or ~15+GB.. Approximately 256 MB / minute
    leaking.
    
    /proc/meminfo | grep SUnreclaim...
    
    SUnreclaim:      6752128 kB
    SUnreclaim:      6874880 kB
    SUnreclaim:      7238080 kB
    ....
    SUnreclaim:     22307264 kB
    SUnreclaim:     22485888 kB
    SUnreclaim:     22720256 kB
    
    When testcases with T10 enabled call into __blkdev_direct_IO_simple,
    code doesn't free memory allocated by bio_integrity_alloc. The patch
    fixes the issue. HTX has been run with +60 hours without failure."
    
    Since __blkdev_direct_IO_simple() allocates the bio on the stack, it
    doesn't go through the regular bio free. This means that any ancillary
    data allocated with the bio through the stack is not freed. Hence, we
    can leak the integrity data associated with the bio, if the device is
    using DIF/DIX.
    
    Fix this by providing a bio_uninit() and export it, so that we can use
    it to free this data. Note that this is a minimal fix for this issue.
    Any current user of bio's that are allocated outside of
    bio_alloc_bioset() suffers from this issue, most notably some drivers.
    We will fix those in a more comprehensive patch for 4.13. This also
    means that the commit marked as being fixed by this isn't the real
    culprit, it's just the most obvious one out there.
    
    Fixes: 542ff7bf ("block: new direct I/O implementation")
    Reported-by: default avatarWen Xiong <wenxiong@linux.vnet.ibm.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    9ae3b3f5
bio.c 50.8 KB