107 lines
4.4 KiB
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107 lines
4.4 KiB
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Path: news.gmane.org!not-for-mail
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From: Niels de Vos <ndevos@redhat.com>
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Newsgroups: gmane.linux.kernel,gmane.linux.file-systems
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Subject: [PATCH v2] fs: Invalidate the cache for a parent block-device if fsync() is called for a partition
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Date: Mon, 23 Jan 2012 10:38:29 +0000
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Lines: 58
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Approved: news@gmane.org
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Message-ID: <1327315109-7740-1-git-send-email-ndevos@redhat.com>
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References: <4F19356E.3020708@redhat.com>
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NNTP-Posting-Date: Mon, 23 Jan 2012 10:41:03 +0000 (UTC)
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Cc: linux-kernel@vger.kernel.org, Niels de Vos <ndevos@redhat.com>,
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"Bryn M. Reeves" <bmr@redhat.com>,
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Mikulas Patocka <mpatocka@redhat.com>
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To: linux-fsdevel@vger.kernel.org
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Original-X-From: linux-kernel-owner@vger.kernel.org Mon Jan 23 11:40:58 2012
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Mon, 23 Jan 2012 05:40:46 -0500
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In-Reply-To: <4F19356E.3020708@redhat.com>
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Xref: news.gmane.org gmane.linux.kernel:1242432 gmane.linux.file-systems:60751
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Archived-At: <http://permalink.gmane.org/gmane.linux.kernel/1242432>
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Executing an fsync() on a file-descriptor of a partition flushes the
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caches for that partition by calling blkdev_issue_flush(). However, it
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seems that reading data through the parent device will still return the
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old cached data.
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The cache for the block-device is not synced if the block-device is kept
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open (due to a mounted partition, for example). Only when all users for
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the disk have exited, the cache for the disk is made consistent again.
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Calling invalidate_bdev() on the parent block-device in case
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blkdev_fsync() was called for a partition, fixes this.
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The problem can be worked around by forcing the caches to be flushed
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with either
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# blockdev --flushbufs ${dev_disk}
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or
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# echo 3 > /proc/sys/vm/drop_caches
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CC: Bryn M. Reeves <bmr@redhat.com>
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CC: Mikulas Patocka <mpatocka@redhat.com>
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Signed-off-by: Niels de Vos <ndevos@redhat.com>
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---
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v2:
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- Do not call invalidate_bdev() from blkdev_issue_flush() and prevent
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performance degration with journalled filesystems.
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Suggested was to call invalidate_bdev() in fsync_bdev(), but this is
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not in the call-path of mkfs.ext3 and similar tools. Hence the issue
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persists.
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- Correct phrasing a little, changing ioctl-BLKFLSBUF is not required.
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- This issue also occurs when doing an ioctl-BLKFLSBUF on a partition.
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Reading the whole disk will still return cached data. If this is an
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issue, it will need a seperate patch.
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---
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fs/block_dev.c | 4 ++++
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1 files changed, 4 insertions(+), 0 deletions(-)
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diff --git a/fs/block_dev.c b/fs/block_dev.c
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index 0e575d1..433c4de 100644
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--- a/fs/block_dev.c
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+++ b/fs/block_dev.c
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@@ -424,6 +424,10 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
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if (error == -EOPNOTSUPP)
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error = 0;
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+ /* invalidate parent block_device */
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+ if (!error && bdev != bdev->bd_contains)
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+ invalidate_bdev(bdev->bd_contains);
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+
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return error;
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}
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EXPORT_SYMBOL(blkdev_fsync);
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--
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1.7.6.5
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