The patch titled
Subject: fs: don't flush pagecache when expanding block device
has been added to the -mm tree. Its filename is
fs-dont-flush-pagecache-when-expanding-block-device.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-dont-flush-pagecache-when-expanding-block-device.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-dont-flush-pagecache-when-expanding-block-device.patch
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------------------------------------------------------
From: shunki-fujita <shunki-fujita@xxxxxxxxxxxx>
Subject: fs: don't flush pagecache when expanding block device
When changing the size of a block device, its all caches are freed. It's
necessary on shrinking to prevent spurious I/Os to the disappeared region.
However, on expanding, such kind of I/Os doesn't happen.
Similar things can be considered for btrfs filesystem resize and
resize2fs, but they are designed not to drop caches when expanding.
Therefore this patch removes unnecessary cache drop.
Link: http://lkml.kernel.org/r/1521457240-153390-1-git-send-email-shunki-fujita@xxxxxxxxxxxx
Signed-off-by: Shunki Fujita <shunki-fujita@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/block_dev.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff -puN fs/block_dev.c~fs-dont-flush-pagecache-when-expanding-block-device fs/block_dev.c
--- a/fs/block_dev.c~fs-dont-flush-pagecache-when-expanding-block-device
+++ a/fs/block_dev.c
@@ -1324,7 +1324,8 @@ static void flush_disk(struct block_devi
* @bdev: struct bdev to adjust.
*
* This routine checks to see if the bdev size does not match the disk size
- * and adjusts it if it differs.
+ * and adjusts it if it differs. When shrinking the bdev size, its all caches
+ * are freed.
*/
void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
{
@@ -1337,7 +1338,8 @@ void check_disk_size_change(struct gendi
"%s: detected capacity change from %lld to %lld\n",
disk->disk_name, bdev_size, disk_size);
i_size_write(bdev->bd_inode, disk_size);
- flush_disk(bdev, false);
+ if (bdev_size > disk_size)
+ flush_disk(bdev, false);
}
}
EXPORT_SYMBOL(check_disk_size_change);
_
Patches currently in -mm which might be from shunki-fujita@xxxxxxxxxxxx are
fs-dont-flush-pagecache-when-expanding-block-device.patch
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