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Subject[PATCH] fs: don't flush pagecache when expanding block device
Date
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 cache drops when expanding.
Therefore this patch removes unnecessary cache drop.

Signed-off-by: Shunki Fujita <shunki-fujita@cybozu.co.jp>
---
fs/block_dev.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index fe09ef9..243f4002 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1337,7 +1337,14 @@ void check_disk_size_change(struct gendisk *disk, struct block_device *bdev)
"%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);
+ } else {
+ if (!bdev->bd_disk)
+ return;
+ if (disk_part_scan_enabled(bdev->bd_disk))
+ bdev->bd_invalidated = 1;
+ }
}
}
EXPORT_SYMBOL(check_disk_size_change);
--
2.7.4
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