[PATCH v8 27/41] btrfs: introduce dedicated data write path for ZONED mode

From: Naohiro Aota <naohiro.aota@wdc.com>
To: linux-btrfs@vger.kernel.org, dsterba@suse.com
Cc: hare@suse.com, linux-fsdevel@vger.kernel.org,
	Naohiro Aota <naohiro.aota@wdc.com>
Subject: [PATCH v8 27/41] btrfs: introduce dedicated data write path for ZONED mode
Date: Fri,  2 Oct 2020 03:36:34 +0900	[thread overview]
Message-ID: <2a95e45089e9f9b1425e8fbe0acac966ee93d07b.1601574234.git.naohiro.aota@wdc.com> (raw)
In-Reply-To: <dece91bca322ce44bed19f2b0f460fa5ded2e512.1601574234.git.naohiro.aota@wdc.com>

If more than one IO is issued for one file extent, these IO can be written
in a separate region 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.

Normal (buffered, uncompressed, not pre-allocated) write path (=
cow_file_range()) sometime does not follow the rule. It can write a part of
an ordered extent when specified a region to write e.g., called from
fdatasync().

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

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/inode.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 37d85c062f3a..46eba6c7792b 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_fs_incompat(inode->root->fs_info, ZONED);
 
 	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,
-- 
2.27.0

