On Wed 01-06-16 16:44:45, Christoph Hellwig wrote:
> Add infrastructure for multipage buffered writes. This is implemented
> using an main iterator that applies an actor function to a range that
> can be written.
>
> This infrastucture is used to implement a buffered write helper, one
> to zero file ranges and one to implement the ->page_mkwrite VM
> operations. All of them borrow a fair amount of code from fs/buffers.
> for now by using an internal version of __block_write_begin that
> gets passed an iomap and builds the corresponding buffer head.
>
> The file system is gets a set of paired ->iomap_begin and ->iomap_end
> calls which allow it to map/reserve a range and get a notification
> once the write code is finished with it.
>
> Based on earlier code from Dave Chinner.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Bob Peterson <rpeterso@xxxxxxxxxx>
When reading through the patch I've noticed two minor errors in the
comments:
...
> +static loff_t
> +iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> + struct iomap_ops *ops, void *data, iomap_actor_t actor)
> +{
> + struct iomap iomap = { 0 };
> + loff_t written = 0, ret;
> +
> + /*
> + * Need to map a range from start position for count bytes. This can
^^^^ length
...
> struct iomap {
> - sector_t blkno; /* first sector of mapping */
> - loff_t offset; /* file offset of mapping, bytes */
> - u64 length; /* length of mapping, bytes */
> - int type; /* type of mapping */
> + sector_t blkno; /* first sector of mapping, fs blocks */
This is actually in 512-byte units, not in fs blocks as the comment
suggests, right?
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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