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

[Chao Yu via Linux-f2fs-devel]

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 <c...@kernel.org>
---
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



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