Encapsulate the inode lock needed for serializing the data relocation
writes on a zoned filesystem into a helper.

This streamlines the code reading flow and hides special casing for
zoned filesystems.

Signed-off-by: Johannes Thumshirn <redacted>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/extent_io.c |  8 ++------
 fs/btrfs/zoned.h     | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1a67f4b3986b..cc27e6e6d6ce 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c

@@ -5184,8 +5184,6 @@ int extent_writepages(struct address_space *mapping,
 		      struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
-	const bool data_reloc = btrfs_is_data_reloc_root(BTRFS_I(inode)->root);
-	const bool zoned = btrfs_is_zoned(BTRFS_I(inode)->root->fs_info);
 	int ret = 0;
 	struct extent_page_data epd = {
 		.bio_ctrl = { 0 },

@@ -5197,11 +5195,9 @@ int extent_writepages(struct address_space *mapping,
 	 * Allow only a single thread to do the reloc work in zoned mode to
 	 * protect the write pointer updates.
 	 */
-	if (data_reloc && zoned)
-		btrfs_inode_lock(inode, 0);
+	btrfs_zoned_data_reloc_lock(inode);
 	ret = extent_write_cache_pages(mapping, wbc, &epd);
-	if (data_reloc && zoned)
-		btrfs_inode_unlock(inode, 0);
+	btrfs_zoned_data_reloc_unlock(inode);
 	ASSERT(ret <= 0);
 	if (ret < 0) {
 		end_write_bio(&epd, ret);

diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index 4344f4818389..e3eaf03a3422 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h

@@ -8,6 +8,7 @@
 #include "volumes.h"
 #include "disk-io.h"
 #include "block-group.h"
+#include "btrfs_inode.h"
 
 /*
  * Block groups with more than this value (percents) of unusable space will be

@@ -354,4 +355,20 @@ static inline void btrfs_clear_treelog_bg(struct btrfs_block_group *bg)
 	spin_unlock(&fs_info->treelog_bg_lock);
 }
 
+static inline void btrfs_zoned_data_reloc_lock(struct inode *inode)