[PATCH RFC 6/8] ext4: Add support for FALLOC_FL_PROVISION

[Sarthak Kukreti]

From: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>

Once ext4 is done mapping blocks for an fallocate() request, send
out an FALLOC_FL_PROVISION request to the underlying layer to
ensure that the space is provisioned for the newly allocated extent
or indirect blocks.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>
---
 fs/ext4/ext4.h         |  2 ++
 fs/ext4/extents.c      | 15 ++++++++++++++-
 fs/ext4/indirect.c     |  9 +++++++++
 include/linux/blkdev.h | 11 +++++++++++
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9bca5565547b..ec0871e687c1 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -675,6 +675,8 @@ enum {
 #define EXT4_GET_BLOCKS_IO_SUBMIT		0x0400
 	/* Caller is in the atomic contex, find extent if it has been cached */
 #define EXT4_GET_BLOCKS_CACHED_NOWAIT		0x0800
+	/* Provision blocks on underlying storage */
+#define EXT4_GET_BLOCKS_PROVISION		0x1000
 
 /*
  * The bit position of these flags must not overlap with any of the
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c148bb97b527..7a096144b7f8 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4356,6 +4356,13 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 		}
 	}
 
+	/* Attempt to provision blocks on underlying storage */
+	if (flags & EXT4_GET_BLOCKS_PROVISION) {
+		err = sb_issue_provision(inode->i_sb, pblk, ar.len, GFP_NOFS);
+		if (err)
+			goto out;
+	}
+
 	/*
 	 * Cache the extent and update transaction to commit on fdatasync only
 	 * when it is _not_ an unwritten extent.
@@ -4690,7 +4697,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	/* Return error if mode is not supported */
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
 		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
-		     FALLOC_FL_INSERT_RANGE))
+		     FALLOC_FL_INSERT_RANGE | FALLOC_FL_PROVISION))
 		return -EOPNOTSUPP;
 
 	inode_lock(inode);
@@ -4750,6 +4757,12 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	if (ret)
 		goto out;
 
+	/* Ensure that preallocation provisions the blocks on the underlying
+	 * storage device.
+	 */
+	if (mode & FALLOC_FL_PROVISION)
+		flags |= EXT4_GET_BLOCKS_PROVISION;
+
 	ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size, flags);
 	if (ret)
 		goto out;
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 860fc5119009..860a2560872b 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -640,6 +640,15 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
 	if (err)
 		goto cleanup;
 
+	/* Attempt to provision blocks on underlying storage */
+	if (flags & EXT4_GET_BLOCKS_PROVISION) {
+		err = sb_issue_provision(inode->i_sb,
+					 le32_to_cpu(chain[depth-1].key),
+					 ar.len, GFP_NOFS);
+		if (err)
+			goto out;
+	}
+
 	map->m_flags |= EXT4_MAP_NEW;
 
 	ext4_update_inode_fsync_trans(handle, inode, 1);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a58496d3f922..26b41a6c12f4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1107,6 +1107,17 @@ static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,
 				    gfp_mask, 0);
 }
 
+static inline int sb_issue_provision(struct super_block *sb, sector_t block,
+		sector_t nr_blocks, gfp_t gfp_mask)
+{
+	return blkdev_issue_provision(sb->s_bdev,
+				      block << (sb->s_blocksize_bits -
+					      SECTOR_SHIFT),
+				      nr_blocks << (sb->s_blocksize_bits -
+						    SECTOR_SHIFT),
+				      gfp_mask);
+}
+
 static inline bool bdev_is_partition(struct block_device *bdev)
 {
 	return bdev->bd_partno;
-- 
2.31.0