On 2011-08-22, at 2:49 PM, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>
> Add a generic_file_llseek variant to the VFS that allows passing in
> the current file size, instead of always using inode->i_size.
> This can be used to eliminate some cut'n'paste seek code in ext4.
I think your commit comment is incorrect. It should read:
Add a generic_file_llseek_size() variant to the VFS that allows passing
in the maximum file size, instead of always using inode->i_sb->s_maxbytes.
This can be used to eliminate some cut'n'paste seek code in ext4.
Also, the function prototype in fs.h should take "loff_t maxbytes" instead
of "loff_t size".
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> ---
> fs/read_write.c | 34 +++++++++++++++++++++++++++-------
> include/linux/fs.h | 2 ++
> 2 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 8e8aab3..3d55cc6 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -51,14 +51,14 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, loff_t offse
> }
>
> /**
> - * generic_file_llseek - generic llseek implementation for regular files
> + * generic_file_llseek_size - generic llseek implementation for regular files
> * @file: file structure to seek on
> * @offset: file offset to seek to
> * @origin: type of seek
> + * @size: max size of file system
> *
> - * This is a generic implemenation of ->llseek useable for all normal local
> - * filesystems. It just updates the file offset to the value specified by
> - * @offset and @origin under i_mutex.
> + * Variant of generic_file_llseek that allows passing in a custom
> + * file size.
> *
> * Synchronization:
> * SEEK_SET is unsynchronized (but atomic on 64bit platforms)
> @@ -67,7 +67,8 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, loff_t offse
> * SEEK_END
> */
> loff_t
> -generic_file_llseek(struct file *file, loff_t offset, int origin)
> +generic_file_llseek_size(struct file *file, loff_t offset, int origin,
> + loff_t maxsize)
> {
> struct inode *inode = file->f_mapping->host;
>
> @@ -91,7 +92,7 @@ generic_file_llseek(struct file *file, loff_t offset, int origin)
> */
> spin_lock(&file->f_lock);
> offset = lseek_execute(file, inode, file->f_pos + offset,
> - inode->i_sb->s_maxbytes);
> + maxsize);
> spin_unlock(&file->f_lock);
> return offset;
> case SEEK_DATA:
> @@ -113,7 +114,26 @@ generic_file_llseek(struct file *file, loff_t offset, int origin)
> break;
> }
>
> - return lseek_execute(file, inode, offset, inode->i_sb->s_maxbytes);
> + return lseek_execute(file, inode, offset, maxsize);
> +}
> +EXPORT_SYMBOL(generic_file_llseek_size);
> +
> +/**
> + * generic_file_llseek - generic llseek implementation for regular files
> + * @file: file structure to seek on
> + * @offset: file offset to seek to
> + * @origin: type of seek
> + *
> + * This is a generic implemenation of ->llseek useable for all normal local
> + * filesystems. It just updates the file offset to the value specified by
> + * @offset and @origin under i_mutex.
> + */
> +loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
> +{
> + struct inode *inode = file->f_mapping->host;
> +
> + return generic_file_llseek_size(file, offset, origin,
> + inode->i_sb->s_maxbytes);
> }
> EXPORT_SYMBOL(generic_file_llseek);
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3417259..d64b601 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2395,6 +2395,8 @@ file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
> extern loff_t noop_llseek(struct file *file, loff_t offset, int origin);
> extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
> extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
> +extern loff_t generic_file_llseek_size(struct file *file, loff_t offset, int origin,
> + loff_t size);
> extern int generic_file_open(struct inode * inode, struct file * filp);
> extern int nonseekable_open(struct inode * inode, struct file * filp);
>
> --
> 1.7.4.4
>
> --
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Cheers, Andreas
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