On Mon, Mar 10, 2025 at 06:39:46PM +0000, John Garry wrote:
> Dave Chinner thought that names IOMAP_ATOMIC_HW and IOMAP_ATOMIC_SW were
> not appropopiate. Specifically because IOMAP_ATOMIC_HW could actually be
> realised with a SW-based method in the block or md/dm layers.
>
> So rename to IOMAP_ATOMIC_BIO and IOMAP_ATOMIC_FS.
Looking over the entire series and the already merged iomap code:
there should be no reason at all for having IOMAP_ATOMIC_FS.
The only thing it does is to branch out to
xfs_atomic_write_sw_iomap_begin from xfs_atomic_write_iomap_begin.
You can do that in a much simpler and nicer way by just having
different iomap_ops for the bio based vs file system based atomics.
I agree with dave that bio is a better term for the bio based
atomic, but please use the IOMAP_ATOMIC_BIO name above instead
of the IOMAP_BIO_ATOMIC actually used in the code if you change
it.
> */
> static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
> - const struct iomap *iomap, bool use_fua, bool atomic_hw)
> + const struct iomap *iomap, bool use_fua, bool bio_atomic)
Not new here, but these two bools are pretty ugly.
I'd rather have a
blk_opf_t extra_flags;
in the caller that gets REQ_FUA and REQ_ATOMIC assigned as needed,
and then just clear
>
> - if (atomic_hw && length != iter->len)
> + if (bio_atomic && length != iter->len)
> return -EINVAL;
This could really use a comment explaining what the check is for.
> - if (WARN_ON_ONCE(atomic_hw && n != length)) {
> + if (WARN_ON_ONCE(bio_atomic && n != length)) {
Same.
> -#define IOMAP_ATOMIC_HW (1 << 9) /* HW-based torn-write protection */
> -#define IOMAP_DONTCACHE (1 << 10)
> -#define IOMAP_ATOMIC_SW (1 << 11)/* SW-based torn-write protection */
> +#define IOMAP_DONTCACHE (1 << 9)
> +#define IOMAP_BIO_ATOMIC (1 << 10) /* Use REQ_ATOMIC on single bio */
> +#define IOMAP_FS_ATOMIC (1 << 11) /* FS-based torn-write protection */
Please also fix the overly long lines here by moving the comments
above the definitions. That should also give you enough space to
expand the comment into a full sentence describing the flag fully.
