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    Subject[PATCH v2] fs: Invalidate the cache for a parent block-device if fsync() is called for a partition
    Executing an fsync() on a file-descriptor of a partition flushes the
    caches for that partition by calling blkdev_issue_flush(). However, it
    seems that reading data through the parent device will still return the
    old cached data.

    The cache for the block-device is not synced if the block-device is kept
    open (due to a mounted partition, for example). Only when all users for
    the disk have exited, the cache for the disk is made consistent again.

    Calling invalidate_bdev() on the parent block-device in case
    blkdev_fsync() was called for a partition, fixes this.

    The problem can be worked around by forcing the caches to be flushed
    with either
    # blockdev --flushbufs ${dev_disk}
    # echo 3 > /proc/sys/vm/drop_caches

    CC: Bryn M. Reeves <>
    CC: Mikulas Patocka <>
    Signed-off-by: Niels de Vos <>

    - Do not call invalidate_bdev() from blkdev_issue_flush() and prevent
    performance degration with journalled filesystems.

    Suggested was to call invalidate_bdev() in fsync_bdev(), but this is
    not in the call-path of mkfs.ext3 and similar tools. Hence the issue

    - Correct phrasing a little, changing ioctl-BLKFLSBUF is not required.

    - This issue also occurs when doing an ioctl-BLKFLSBUF on a partition.
    Reading the whole disk will still return cached data. If this is an
    issue, it will need a seperate patch.
    fs/block_dev.c | 4 ++++
    1 files changed, 4 insertions(+), 0 deletions(-)

    diff --git a/fs/block_dev.c b/fs/block_dev.c
    index 0e575d1..433c4de 100644
    --- a/fs/block_dev.c
    +++ b/fs/block_dev.c
    @@ -424,6 +424,10 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
    if (error == -EOPNOTSUPP)
    error = 0;

    + /* invalidate parent block_device */
    + if (!error && bdev != bdev->bd_contains)
    + invalidate_bdev(bdev->bd_contains);
    return error;

     \ /
      Last update: 2012-01-23 11:43    [W:0.023 / U:10.940 seconds]
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