linux-kernel - [PATCH] fs: Remove FIXME comment in generic_write

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Date:   Fri, 31 Dec 2021 02:57:50 -0500
From:   Tal Zussman <tz2294@...umbia.edu>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        "open list:FILESYSTEMS (VFS and infrastructure)" 
        <linux-fsdevel@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, tz2294@...umbia.edu,
        Xijiao Li <xl2950@...umbia.edu>,
        Hans Montero <hjm2133@...umbia.edu>,
        "Theodore Ts'o" <tytso@....edu>,
        OS-TA <cucs4118-tas@...glegroups.com>
Subject: [PATCH] fs: Remove FIXME comment in generic_write_checks()

This patch removes an unnecessary comment that had to do with block special
files from `generic_write_checks()`.

The comment, originally added in Linux v2.4.14.9, was to clarify that we only
set `pos` to the file size when the file was opened with `O_APPEND` if the file
wasn't a block special file. Prior to Linux v2.4, block special files had a
different `write()` function which was unified into a generic `write()` function
in Linux v2.4. This generic `write()` function called `generic_write_checks()`.
For more details, see this earlier conversation:
https://lore.kernel.org/linux-fsdevel/Yc4Czk5A+p5p2Y4W@mit.edu/

Currently, block special devices have their own `write_iter()` function and no
longer share the same `generic_write_checks()`, therefore rendering the comment
irrelevant.

Signed-off-by: Tal Zussman <tz2294@...umbia.edu>
Co-authored-by: Xijiao Li <xl2950@...umbia.edu>
Co-authored-by: Hans Montero <hjm2133@...umbia.edu>
Suggested-by: Theodore Ts'o <tytso@....edu>
---
 fs/read_write.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 0074afa7ecb3..0173dc7183c9 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1637,7 +1637,6 @@ ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	if (!iov_iter_count(from))
 		return 0;

-	/* FIXME: this is for backwards compatibility with 2.4 */
 	if (iocb->ki_flags & IOCB_APPEND)
 		iocb->ki_pos = i_size_read(inode);

-- 
2.20.1