[PATCH] fs: fix misleading comments in read_write.c

[PATCH] fs: fix misleading comments in read_write.c

[Yingchao Deng]

generic_write_checks() returns the number of bytes that may be written
(possibly truncated by generic_write_check_limits()), not zero.  The
comment was likely copied from generic_copy_file_checks(), which is the
analogous function for copy_file_range() and does return 0 on success.

Also, no_seek_end_llseek() and no_seek_end_llseek_size() are helpers for
files that do not support SEEK_END (they only handle SEEK_SET and
SEEK_CUR), not for "fixed-sized devices"; that description was copied
from fixed_size_llseek().

Signed-off-by: Yingchao Deng <dengyingchao@kylinsec.com.cn>
---
 fs/read_write.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index e8c14e2760b2..4da846a2bf17 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -274,7 +274,7 @@ loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t si
 EXPORT_SYMBOL(fixed_size_llseek);
 
 /**
- * no_seek_end_llseek - llseek implementation for fixed-sized devices
+ * no_seek_end_llseek - llseek implementation for files without SEEK_END
  * @file:	file structure to seek on
  * @offset:	file offset to seek to
  * @whence:	type of seek
@@ -293,7 +293,7 @@ loff_t no_seek_end_llseek(struct file *file, loff_t offset, int whence)
 EXPORT_SYMBOL(no_seek_end_llseek);
 
 /**
- * no_seek_end_llseek_size - llseek implementation for fixed-sized devices
+ * no_seek_end_llseek_size - llseek implementation for files without SEEK_END
  * @file:	file structure to seek on
  * @offset:	file offset to seek to
  * @whence:	type of seek
@@ -1761,8 +1761,8 @@ EXPORT_SYMBOL(generic_write_checks_count);
  * Performs necessary checks before doing a write
  *
  * Can adjust writing position or amount of bytes to write.
- * Returns appropriate error code that caller should return or
- * zero in case that write should be allowed.
+ * Returns the number of bytes that may be written on success (which
+ * may be less than requested if truncated), or a negative error code.
  */
 ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 {
-- 
2.33.0

Re: [PATCH] fs: fix misleading comments in read_write.c

[Jan Kara]

On Mon 14-09-26 15:53:37, Yingchao Deng wrote:
> generic_write_checks() returns the number of bytes that may be written
> (possibly truncated by generic_write_check_limits()), not zero.  The
> comment was likely copied from generic_copy_file_checks(), which is the
> analogous function for copy_file_range() and does return 0 on success.
> 
> Also, no_seek_end_llseek() and no_seek_end_llseek_size() are helpers for
> files that do not support SEEK_END (they only handle SEEK_SET and
> SEEK_CUR), not for "fixed-sized devices"; that description was copied
> from fixed_size_llseek().
> 
> Signed-off-by: Yingchao Deng <dengyingchao@kylinsec.com.cn>

Nice, thanks. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/read_write.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index e8c14e2760b2..4da846a2bf17 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -274,7 +274,7 @@ loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t si
>  EXPORT_SYMBOL(fixed_size_llseek);
>  
>  /**
> - * no_seek_end_llseek - llseek implementation for fixed-sized devices
> + * no_seek_end_llseek - llseek implementation for files without SEEK_END
>   * @file:	file structure to seek on
>   * @offset:	file offset to seek to
>   * @whence:	type of seek
> @@ -293,7 +293,7 @@ loff_t no_seek_end_llseek(struct file *file, loff_t offset, int whence)
>  EXPORT_SYMBOL(no_seek_end_llseek);
>  
>  /**
> - * no_seek_end_llseek_size - llseek implementation for fixed-sized devices
> + * no_seek_end_llseek_size - llseek implementation for files without SEEK_END
>   * @file:	file structure to seek on
>   * @offset:	file offset to seek to
>   * @whence:	type of seek
> @@ -1761,8 +1761,8 @@ EXPORT_SYMBOL(generic_write_checks_count);
>   * Performs necessary checks before doing a write
>   *
>   * Can adjust writing position or amount of bytes to write.
> - * Returns appropriate error code that caller should return or
> - * zero in case that write should be allowed.
> + * Returns the number of bytes that may be written on success (which
> + * may be less than requested if truncated), or a negative error code.
>   */
>  ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
>  {
> -- 
> 2.33.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] fs: fix misleading comments in read_write.c

[Christian Brauner]

On Mon, 14 Sep 2026 15:53:37 +0800, Yingchao Deng wrote:
> generic_write_checks() returns the number of bytes that may be written
> (possibly truncated by generic_write_check_limits()), not zero.  The
> comment was likely copied from generic_copy_file_checks(), which is the
> analogous function for copy_file_range() and does return 0 on success.
> 
> Also, no_seek_end_llseek() and no_seek_end_llseek_size() are helpers for
> files that do not support SEEK_END (they only handle SEEK_SET and
> SEEK_CUR), not for "fixed-sized devices"; that description was copied
> from fixed_size_llseek().
> 
> [...]

Applied to the vfs-7.4.misc branch of the vfs/vfs.git tree.
Patches in the vfs-7.4.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-7.4.misc

[1/1] fs: fix misleading comments in read_write.c
      https://git.kernel.org/vfs/vfs/c/73a1ab6d7e14