[RF[CRAP] 2/2] xfs: stop using set_blocksize

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

XFS has its own buffer cache for metadata that uses submit_bio, which
means that it no longer uses the block device pagecache for anything.
Create a more lightweight helper that runs the blocksize checks and
flushes dirty data and use that instead.  No more truncating the
pagecache because why would XFS care? ;)

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 include/linux/blkdev.h |    1 +
 block/bdev.c           |   23 +++++++++++++++++++++++
 fs/xfs/xfs_buf.c       |    9 ++++++---
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f442639dfae224..ae83dd12351c2e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1618,6 +1618,7 @@ static inline void bio_end_io_acct(struct bio *bio, unsigned long start_time)
 	return bio_end_io_acct_remapped(bio, start_time, bio->bi_bdev);
 }
 
+int bdev_use_blocksize(struct file *file, int size);
 int set_blocksize(struct file *file, int size);
 
 int lookup_bdev(const char *pathname, dev_t *dev);
diff --git a/block/bdev.c b/block/bdev.c
index 0cbdac46d98d86..201d61d743592e 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -152,6 +152,29 @@ static void set_init_blocksize(struct block_device *bdev)
 				    get_order(bsize), get_order(bsize));
 }
 
+/*
+ * For bdev filesystems that do not use buffer heads, check that this block
+ * size is acceptable and flush dirty pagecache to disk.
+ */
+int bdev_use_blocksize(struct file *file, int size)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct block_device *bdev = I_BDEV(inode);
+
+	if (blk_validate_block_size(size))
+		return -EINVAL;
+
+	/* Size cannot be smaller than the size supported by the device */
+	if (size < bdev_logical_block_size(bdev))
+		return -EINVAL;
+
+	if (!file->private_data)
+		return -EINVAL;
+
+	return sync_blockdev(bdev);
+}
+EXPORT_SYMBOL_GPL(bdev_use_blocksize);
+
 int set_blocksize(struct file *file, int size)
 {
 	struct inode *inode = file->f_mapping->host;
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 8e7f1b324b3bea..2c8531103c01bb 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1718,14 +1718,17 @@ xfs_setsize_buftarg(
 	struct xfs_buftarg	*btp,
 	unsigned int		sectorsize)
 {
+	int			error;
+
 	/* Set up metadata sector size info */
 	btp->bt_meta_sectorsize = sectorsize;
 	btp->bt_meta_sectormask = sectorsize - 1;
 
-	if (set_blocksize(btp->bt_bdev_file, sectorsize)) {
+	error = bdev_use_blocksize(btp->bt_bdev_file, sectorsize);
+	if (error) {
 		xfs_warn(btp->bt_mount,
-			"Cannot set_blocksize to %u on device %pg",
-			sectorsize, btp->bt_bdev);
+			"Cannot use blocksize %u on device %pg, err %d",
+			sectorsize, btp->bt_bdev, error);
 		return -EINVAL;
 	}