[RFC PATCH 7/5] xfs: add block device provisioning for fallocate

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

Provision space in the block device for preallocated file space when
userspace asks for it. Make sure to do this outside of transaction
context so it can fail without causing a filesystem shutdown.

XXX: async provisioning submission/completion interface would be
really useful here....

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_bmap_util.c | 42 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index fcefab687285..5dddd1e7bc47 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -772,6 +772,37 @@ xfs_free_eofblocks(
 	return error;
 }
 
+static int
+xfs_bmap_provision_blocks(
+	struct xfs_inode	*ip,
+	struct xfs_bmbt_irec	*imap,
+	int			nimaps)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_buftarg	*target;
+	int			i;
+
+	if (!xfs_is_provisioning_blocks(mp))
+		return 0;
+
+	target = xfs_inode_buftarg(ip);
+	if (!target->bt_needs_provisioning)
+		return 0;
+
+	for (i = 0; i < nimaps; i++) {
+		int	error;
+
+		error = blkdev_issue_provision(target->bt_bdev,
+				XFS_FSB_TO_DADDR(mp, imap->br_startblock),
+				XFS_FSB_TO_BB(mp, imap->br_blockcount),
+				GFP_KERNEL, 0);
+		ASSERT(error != -EOPNOTSUPP);
+		if (error)
+			return error;
+	}
+	return 0;
+}
+
 int
 xfs_alloc_file_space(
 	struct xfs_inode	*ip,
@@ -780,7 +811,6 @@ xfs_alloc_file_space(
 {
 	xfs_mount_t		*mp = ip->i_mount;
 	xfs_off_t		count;
-	xfs_filblks_t		allocated_fsb;
 	xfs_filblks_t		allocatesize_fsb;
 	xfs_extlen_t		extsz, temp;
 	xfs_fileoff_t		startoffset_fsb;
@@ -884,15 +914,17 @@ xfs_alloc_file_space(
 		if (error)
 			break;
 
-		allocated_fsb = imapp->br_blockcount;
-
 		if (nimaps == 0) {
 			error = -ENOSPC;
 			break;
 		}
 
-		startoffset_fsb += allocated_fsb;
-		allocatesize_fsb -= allocated_fsb;
+		error = xfs_bmap_provision_blocks(ip, imapp, nimaps);
+		if (error)
+			break;
+
+		startoffset_fsb += imapp->br_blockcount;
+		allocatesize_fsb -= imapp->br_blockcount;
 	}
 
 	return error;