On Fri 30-08-24 15:04:47, Christian Brauner wrote:
> Add a new must_set_pos() helper. We will use it in follow-up patches.
> Temporarily mark it as unused. This is only done to keep the diff small
> and reviewable.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/read_write.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 66ff52860496..acee26989d95 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -85,6 +85,58 @@ loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize)
> }
> EXPORT_SYMBOL(vfs_setpos);
>
> +/**
> + * must_set_pos - check whether f_pos has to be updated
> + * @offset: offset to use
> + * @whence: type of seek operation
> + * @eof: end of file
> + *
> + * Check whether f_pos needs to be updated and update @offset according
> + * to @whence.
> + *
> + * Return: 0 if f_pos doesn't need to be updated, 1 if f_pos has to be
> + * updated, and negative error code on failure.
> + */
> +static __maybe_unused int must_set_pos(struct file *file, loff_t *offset, int whence, loff_t eof)
> +{
> + switch (whence) {
> + case SEEK_END:
> + *offset += eof;
> + break;
> + case SEEK_CUR:
> + /*
> + * Here we special-case the lseek(fd, 0, SEEK_CUR)
> + * position-querying operation. Avoid rewriting the "same"
> + * f_pos value back to the file because a concurrent read(),
> + * write() or lseek() might have altered it
> + */
> + if (*offset == 0) {
> + *offset = file->f_pos;
> + return 0;
> + }
> + break;
> + case SEEK_DATA:
> + /*
> + * In the generic case the entire file is data, so as long as
> + * offset isn't at the end of the file then the offset is data.
> + */
> + if ((unsigned long long)*offset >= eof)
> + return -ENXIO;
> + break;
> + case SEEK_HOLE:
> + /*
> + * There is a virtual hole at the end of the file, so as long as
> + * offset isn't i_size or larger, return i_size.
> + */
> + if ((unsigned long long)*offset >= eof)
> + return -ENXIO;
> + *offset = eof;
> + break;
> + }
> +
> + return 1;
> +}
> +
> /**
> * generic_file_llseek_size - generic llseek implementation for regular files
> * @file: file structure to seek on
>
> --
> 2.45.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
