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@xxxxxxxxxxxx> --- Changes in v2: - Remove unnecessary changes (Since bdev-> bd_invalidated always 0 after check_disk_size_change ()[1]) - Add document of check_disk_size_change () [1] https://github.com/torvalds/linux/blob/master/fs/block_dev.c#L1365-L1366 fs/block_dev.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index fe09ef9..63f1269 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1324,7 +1324,8 @@ static void flush_disk(struct block_device *bdev, bool kill_dirty) * @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 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); } } EXPORT_SYMBOL(check_disk_size_change); -- 2.7.4
