On Tue, Feb 04, 2025 at 08:30:36AM -0500, Brian Foster wrote:
> In preparation for more granular iomap_iter advancing, break out
> some of the logic associated with higher level iteration from
> iomap_advance_iter(). Specifically, factor the iomap reset code into
> a separate helper and lift the iomap.length check into the calling
> code, similar to how ->iomap_end() calls are handled.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/iomap/iter.c | 49 ++++++++++++++++++++++++++-----------------------
> 1 file changed, 26 insertions(+), 23 deletions(-)
>
> diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
> index 3790918646af..731ea7267f27 100644
> --- a/fs/iomap/iter.c
> +++ b/fs/iomap/iter.c
> @@ -7,6 +7,13 @@
> #include <linux/iomap.h>
> #include "trace.h"
>
> +static inline void iomap_iter_reset_iomap(struct iomap_iter *iter)
> +{
> + iter->processed = 0;
> + memset(&iter->iomap, 0, sizeof(iter->iomap));
> + memset(&iter->srcmap, 0, sizeof(iter->srcmap));
> +}
> +
> /*
> * Advance to the next range we need to map.
> *
> @@ -14,32 +21,24 @@
> * processed - it was aborted because the extent the iomap spanned may have been
> * changed during the operation. In this case, the iteration behaviour is to
> * remap the unprocessed range of the iter, and that means we may need to remap
> - * even when we've made no progress (i.e. iter->processed = 0). Hence the
> - * "finished iterating" case needs to distinguish between
> - * (processed = 0) meaning we are done and (processed = 0 && stale) meaning we
> - * need to remap the entire remaining range.
> + * even when we've made no progress (i.e. count = 0). Hence the "finished
> + * iterating" case needs to distinguish between (count = 0) meaning we are done
> + * and (count = 0 && stale) meaning we need to remap the entire remaining range.
> */
> -static inline int iomap_iter_advance(struct iomap_iter *iter)
> +static inline int iomap_iter_advance(struct iomap_iter *iter, s64 count)
> {
> bool stale = iter->iomap.flags & IOMAP_F_STALE;
> int ret = 1;
>
> - /* handle the previous iteration (if any) */
> - if (iter->iomap.length) {
> - if (iter->processed < 0)
> - return iter->processed;
> - if (WARN_ON_ONCE(iter->processed > iomap_length(iter)))
> - return -EIO;
> - iter->pos += iter->processed;
> - iter->len -= iter->processed;
> - if (!iter->len || (!iter->processed && !stale))
> - ret = 0;
> - }
> + if (count < 0)
> + return count;
> + if (WARN_ON_ONCE(count > iomap_length(iter)))
> + return -EIO;
> + iter->pos += count;
> + iter->len -= count;
> + if (!iter->len || (!count && !stale))
> + ret = 0;
>
> - /* clear the per iteration state */
> - iter->processed = 0;
> - memset(&iter->iomap, 0, sizeof(iter->iomap));
> - memset(&iter->srcmap, 0, sizeof(iter->srcmap));
Are there any consequences to not resetting the iter if
iter->iomap.length is zero? I think the answer is "no" because callers
are supposed to initialize the iter with zeroes and filesystems are
never supposed to return zero-length iomaps from ->begin_iomap, right?
If the answers are "no" and "yes" then
Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
--D
> return ret;
> }
>
> @@ -82,10 +81,14 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
> return ret;
> }
>
> + /* advance and clear state from the previous iteration */
> trace_iomap_iter(iter, ops, _RET_IP_);
> - ret = iomap_iter_advance(iter);
> - if (ret <= 0)
> - return ret;
> + if (iter->iomap.length) {
> + ret = iomap_iter_advance(iter, iter->processed);
> + iomap_iter_reset_iomap(iter);
> + if (ret <= 0)
> + return ret;
> + }
>
> ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags,
> &iter->iomap, &iter->srcmap);
> --
> 2.48.1
>
>
