From mboxrd@z Thu Jan 1 00:00:00 1970 From: Niels de Vos Subject: [PATCH v2] fs: Invalidate the cache for a parent block-device if fsync() is called for a partition Date: Mon, 23 Jan 2012 10:38:29 +0000 Message-ID: <1327315109-7740-1-git-send-email-ndevos@redhat.com> References: <4F19356E.3020708@redhat.com> Cc: linux-kernel@vger.kernel.org, Niels de Vos , "Bryn M. Reeves" , Mikulas Patocka To: linux-fsdevel@vger.kernel.org Return-path: In-Reply-To: <4F19356E.3020708@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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} or # echo 3 > /proc/sys/vm/drop_caches CC: Bryn M. Reeves CC: Mikulas Patocka Signed-off-by: Niels de Vos --- v2: - 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 persists. - 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; } EXPORT_SYMBOL(blkdev_fsync); -- 1.7.6.5