From: Sarthak Kukreti <sarthakkukr...@chromium.org>

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 <sarthakkukr...@chromium.org>
---
 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

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