[PATCH] f2fs: skip node_change lock for inline data writes

[Seongjae Jeong <jsjlee1020@gmail.com>]

The node_change lock serializes block reservation in the PRE_AIO path
against checkpoint preparation, since block reservation can create
dirty node pages and update checkpoint accounting.

However, writes that remain within the inline data area return before
the block reservation path. Thus, they do not call
inc_valid_block_count(), change a node mapping from NULL_ADDR to
NEW_ADDR, or create a dirty node page as a result of block reservation.
They also do not update total_valid_block_count or
alloc_valid_block_count.

The inline path only copies the existing inline data to the data folio,
sets FI_DATA_EXIST, and marks the inode folio for deferred inline data
flushing. FI_DATA_EXIST can dirty inode metadata, but it does not
reserve a block or update the node mapping and checkpoint accounting
that node_change is intended to serialize.

Skip f2fs_map_lock() for writes that fit within MAX_INLINE_DATA. Keep
the existing locking for inline conversion, which can update filesystem
metadata and requires checkpoint serialization.

Signed-off-by: Seongjae Jeong <jsjlee1020@gmail.com>
---
 fs/f2fs/data.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 21f396ebe22c..f2fb5ef3cb7a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3690,10 +3690,11 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
 
 	/* f2fs_lock_op avoids race between write CP and convert_inline_page */
 	if (f2fs_has_inline_data(inode)) {
-		if (pos + len > MAX_INLINE_DATA(inode))
+		if (pos + len > MAX_INLINE_DATA(inode)) {
 			flag = F2FS_GET_BLOCK_DEFAULT;
-		f2fs_map_lock(sbi, &lc, flag);
-		locked = true;
+			f2fs_map_lock(sbi, &lc, flag);
+			locked = true;
+		}
 	} else if ((pos & PAGE_MASK) >= i_size_read(inode)) {
 		f2fs_map_lock(sbi, &lc, flag);
 		locked = true;
-- 
2.53.0