iomap: split out iomap check and reset logic from iter advance

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@redhat.com>
Link: https://lore.kernel.org/r/20250207143253.314068-3-bfoster@redhat.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
index 3790918646af76395ae7239eb0575d7e63d58658..731ea7267f270735f6790aaca795eaa66efe6377 100644 (file)
--- 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));
        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);