On Fri 30-08-24 15:04:49, Christian Brauner wrote:
> This is similar to generic_file_llseek() but allows the caller to
> specify a cookie that will be updated to indicate that a seek happened.
> Caller's requiring that information in their readdir implementations can
> use that.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/read_write.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 2 ++
> 2 files changed, 46 insertions(+)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index ad93b72cc378..47f7b4e32a53 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -179,6 +179,50 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
> }
> EXPORT_SYMBOL(generic_file_llseek_size);
>
> +/**
> + * generic_llseek_cookie - versioned llseek implementation
> + * @file: file structure to seek on
> + * @offset: file offset to seek to
> + * @whence: type of seek
> + * @cookie: cookie to update
> + *
> + * See generic_file_llseek for a general description and locking assumptions.
> + *
> + * In contrast to generic_file_llseek, this function also resets a
> + * specified cookie to indicate a seek took place.
> + */
> +loff_t generic_llseek_cookie(struct file *file, loff_t offset, int whence,
> + u64 *cookie)
> +{
> + struct inode *inode = file->f_mapping->host;
> + loff_t maxsize = inode->i_sb->s_maxbytes;
> + loff_t eof = i_size_read(inode);
> + int ret;
> +
> + if (WARN_ON_ONCE(!cookie))
> + return -EINVAL;
> +
> + ret = must_set_pos(file, &offset, whence, eof);
> + if (ret < 0)
> + return ret;
> + if (ret == 0)
> + return offset;
> +
> + if (whence == SEEK_CUR) {
> + /*
> + * f_lock protects against read/modify/write race with
> + * other SEEK_CURs. Note that parallel writes and reads
> + * behave like SEEK_SET.
> + */
> + guard(spinlock)(&file->f_lock);
> + return vfs_setpos_cookie(file, file->f_pos + offset, maxsize,
> + cookie);
> + }
> +
> + return vfs_setpos_cookie(file, offset, maxsize, cookie);
> +}
> +EXPORT_SYMBOL(generic_llseek_cookie);
> +
> /**
> * generic_file_llseek - generic llseek implementation for regular files
> * @file: file structure to seek on
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 58c91a52cad1..3e6b3c1afb31 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3202,6 +3202,8 @@ extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize);
> extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
> extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
> int whence, loff_t maxsize, loff_t eof);
> +loff_t generic_llseek_cookie(struct file *file, loff_t offset, int whence,
> + u64 *cookie);
> extern loff_t fixed_size_llseek(struct file *file, loff_t offset,
> int whence, loff_t size);
> extern loff_t no_seek_end_llseek_size(struct file *, loff_t, int, loff_t);
>
> --
> 2.45.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
