[PATCH v2] f2fs: add a fast path in finish_preallocate_blocks()

From: Chao Yu
Date: Tue Mar 25 2025 - 04:13:38 EST


This patch uses i_sem to protect access/update on f2fs_inode_info.flag
in finish_preallocate_blocks(), it avoids grabbing inode_lock() in
each open().

Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
v2:
- get rid of read lock during querying FI_OPENED_FILE once we held
inode lock.
fs/f2fs/file.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index abbcbb5865a3..a71946976761 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -554,19 +554,21 @@ static int f2fs_file_mmap(struct file *file, struct vm_area_struct *vma)

static int finish_preallocate_blocks(struct inode *inode)
{
- int ret;
+ int ret = 0;
+ bool opened;

- inode_lock(inode);
- if (is_inode_flag_set(inode, FI_OPENED_FILE)) {
- inode_unlock(inode);
+ f2fs_down_read(&F2FS_I(inode)->i_sem);
+ opened = is_inode_flag_set(inode, FI_OPENED_FILE);
+ f2fs_up_read(&F2FS_I(inode)->i_sem);
+ if (opened)
return 0;
- }

- if (!file_should_truncate(inode)) {
- set_inode_flag(inode, FI_OPENED_FILE);
- inode_unlock(inode);
- return 0;
- }
+ inode_lock(inode);
+ if (is_inode_flag_set(inode, FI_OPENED_FILE))
+ goto out_unlock;
+
+ if (!file_should_truncate(inode))
+ goto out_update;

f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
filemap_invalidate_lock(inode->i_mapping);
@@ -576,16 +578,17 @@ static int finish_preallocate_blocks(struct inode *inode)

filemap_invalidate_unlock(inode->i_mapping);
f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
-
- if (!ret)
- set_inode_flag(inode, FI_OPENED_FILE);
-
- inode_unlock(inode);
if (ret)
- return ret;
+ goto out_unlock;

file_dont_truncate(inode);
- return 0;
+out_update:
+ f2fs_down_write(&F2FS_I(inode)->i_sem);
+ set_inode_flag(inode, FI_OPENED_FILE);
+ f2fs_up_write(&F2FS_I(inode)->i_sem);
+out_unlock:
+ inode_unlock(inode);
+ return ret;
}

static int f2fs_file_open(struct inode *inode, struct file *filp)
--
2.48.1