[v9,27/41] btrfs: introduce dedicated data write path for ZONED mode

Commit Message

Naohiro Aota Oct. 30, 2020, 1:51 p.m. UTC

If more than one IO is issued for one file extent, these IO can be written
to separate regions on a device. Since we cannot map one file extent to
such a separate area, we need to follow the "one IO == one ordered extent"
rule.

The Normal buffered, uncompressed, not pre-allocated write path (used by
cow_file_range()) sometimes does not follow this rule. It can write a part
of an ordered extent when specified a region to write e.g., when its
called from fdatasync().

Introduces a dedicated (uncompressed buffered) data write path for ZONED
mode. This write path will CoW the region and write it at once.

Signed-off-by: Naohiro Aota <[e-mail]>
---
 fs/btrfs/inode.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

Comments

Josef Bacik Nov. 3, 2020, 3:57 p.m. UTC | #1

On 10/30/20 9:51 AM, Naohiro Aota wrote:
> If more than one IO is issued for one file extent, these IO can be written
> to separate regions on a device. Since we cannot map one file extent to
> such a separate area, we need to follow the "one IO == one ordered extent"
> rule.
> 
> The Normal buffered, uncompressed, not pre-allocated write path (used by
> cow_file_range()) sometimes does not follow this rule. It can write a part
> of an ordered extent when specified a region to write e.g., when its
> called from fdatasync().
> 
> Introduces a dedicated (uncompressed buffered) data write path for ZONED
> mode. This write path will CoW the region and write it at once.
> 
> Signed-off-by: Naohiro Aota <[e-mail]>

This can be modified to work in the way I described in the 'split ordered 
extent' patch, just flesh this out to do all the work together and that way you 
bypass all the ugly splitting stuff.  Thanks,

Josef

Patch

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index bc853a4f22cc..fdc367a39194 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1350,6 +1350,29 @@  static int cow_file_range_async(struct btrfs_inode *inode,
 	return 0;
 }
 
+static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
+				       struct page *locked_page, u64 start,
+				       u64 end, int *page_started,
+				       unsigned long *nr_written)
+{
+	int ret;
+
+	ret = cow_file_range(inode, locked_page, start, end,
+			     page_started, nr_written, 0);
+	if (ret)
+		return ret;
+
+	if (*page_started)
+		return 0;
+
+	__set_page_dirty_nobuffers(locked_page);
+	account_page_redirty(locked_page);
+	extent_write_locked_range(&inode->vfs_inode, start, end, WB_SYNC_ALL);
+	*page_started = 1;
+
+	return 0;
+}
+
 static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
 					u64 bytenr, u64 num_bytes)
 {
@@ -1820,17 +1843,24 @@  int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page
 {
 	int ret;
 	int force_cow = need_force_cow(inode, start, end);
+	int do_compress = inode_can_compress(inode) &&
+		inode_need_compress(inode, start, end);
+	bool zoned = btrfs_is_zoned(inode->root->fs_info);
 
 	if (inode->flags & BTRFS_INODE_NODATACOW && !force_cow) {
+		ASSERT(!zoned);
 		ret = run_delalloc_nocow(inode, locked_page, start, end,
 					 page_started, 1, nr_written);
 	} else if (inode->flags & BTRFS_INODE_PREALLOC && !force_cow) {
+		ASSERT(!zoned);
 		ret = run_delalloc_nocow(inode, locked_page, start, end,
 					 page_started, 0, nr_written);
-	} else if (!inode_can_compress(inode) ||
-		   !inode_need_compress(inode, start, end)) {
+	} else if (!do_compress && !zoned) {
 		ret = cow_file_range(inode, locked_page, start, end,
 				     page_started, nr_written, 1);
+	} else if (!do_compress && zoned) {
+		ret = run_delalloc_zoned(inode, locked_page, start, end,
+					 page_started, nr_written);
 	} else {
 		set_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, &inode->runtime_flags);
 		ret = cow_file_range_async(inode, wbc, locked_page, start, end,