ext4: disambiguate the return value of ext4_dio_write_end_io()

The commit 91562895f803 ("ext4: properly sync file size update after O_SYNC
direct IO") causes confusion about the meaning of the return value of
ext4_dio_write_end_io().

Specifically, when the ext4_handle_inode_extension() operation succeeds,
ext4_dio_write_end_io() directly returns count instead of 0.

This does not cause a bug in the current kernel, but the semantics of the
return value of the ext4_dio_write_end_io() function are wrong, which is
likely to introduce bugs in the future code evolution.

Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20240919082539.381626-1-alexjlzheng@tencent.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 23005f1345a8615405a8892e006d759deb004acd..8e9dfed1c34c1309c905d56a3989d092ba807882 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -392,8 +392,9 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
         */
        if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize) &&
            pos + size <= i_size_read(inode))
-               return size;
-       return ext4_handle_inode_extension(inode, pos, size, size);
+               return 0;
+       error = ext4_handle_inode_extension(inode, pos, size, size);
+       return error < 0 ? error : 0;
 }
 
 static const struct iomap_dio_ops ext4_dio_write_ops = {