Merge patch series "iomap: incremental advance conversion -- phase 2"

Brian Foster <bfoster@redhat.com> says:

Here's phase 2 of the incremental iter advance conversions. This updates
all remaining iomap operations to advance the iter within the operation
and thus removes the need to advance from the core iomap iterator. Once
all operations are switched over, the core advance code is removed and
the processed field is renamed to reflect that it is now a pure status
code.

For context, this was first introduced in a previous series [1] that
focused mainly on the core mechanism and iomap buffered write. This is
because original impetus was to facilitate a folio batch mechanism where
a filesystem can optionally provide a batch of folios to process for a
given mapping (i.e. zero range of an unwritten mapping with dirty folios
in pagecache). That is still WIP, but the broader point is that this was
originally intended as an optional mode until consensus that fell out of
discussion was that it would be preferable to convert over everything.
This presumably facilitates some other future work and simplifies
semantics in the core iteration code.

Patches 1-3 convert over iomap buffered read, direct I/O and various
other remaining ops (swap, etc.). Patches 4-9 convert over the various
DAX iomap operations. Finally, patches 10-12 introduce some cleanups now
that all iomap operations have updated iteration semantics.

* patches from https://lore.kernel.org/r/20250224144757.237706-1-bfoster@redhat.com:
  iomap: introduce a full map advance helper
  iomap: rename iomap_iter processed field to status
  iomap: remove unnecessary advance from iomap_iter()
  dax: advance the iomap_iter on pte and pmd faults
  dax: advance the iomap_iter on dedupe range
  dax: advance the iomap_iter on unshare range
  dax: advance the iomap_iter on zero range
  dax: push advance down into dax_iomap_iter() for read and write
  dax: advance the iomap_iter in the read/write path
  iomap: convert misc simple ops to incremental advance
  iomap: advance the iter on direct I/O
  iomap: advance the iter directly on buffered read

Link: https://lore.kernel.org/r/20250224144757.237706-1-bfoster@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

9 files changed, 164 insertions, 163 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 21b47402b3dc..7fd4cd9a51f2 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1258,7 +1258,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
 }
 #endif /* CONFIG_FS_DAX_PMD */
 
-static s64 dax_unshare_iter(struct iomap_iter *iter)
+static int dax_unshare_iter(struct iomap_iter *iter)
 {
 	struct iomap *iomap = &iter->iomap;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
@@ -1266,11 +1266,11 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
 	u64 copy_len = iomap_length(iter);
 	u32 mod;
 	int id = 0;
-	s64 ret = 0;
+	s64 ret;
 	void *daddr = NULL, *saddr = NULL;
 
 	if (!iomap_want_unshare_iter(iter))
-		return iomap_length(iter);
+		return iomap_iter_advance_full(iter);
 
 	/*
 	 * Extend the file range to be aligned to fsblock/pagesize, because
@@ -1300,14 +1300,14 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
 	if (ret < 0)
 		goto out_unlock;
 
-	if (copy_mc_to_kernel(daddr, saddr, copy_len) == 0)
-		ret = iomap_length(iter);
-	else
+	if (copy_mc_to_kernel(daddr, saddr, copy_len) != 0)
 		ret = -EIO;
 
 out_unlock:
 	dax_read_unlock(id);
-	return dax_mem2blk_err(ret);
+	if (ret < 0)
+		return dax_mem2blk_err(ret);
+	return iomap_iter_advance_full(iter);
 }
 
 int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
@@ -1326,7 +1326,7 @@ int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 
 	iter.len = min(len, size - pos);
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = dax_unshare_iter(&iter);
+		iter.status = dax_unshare_iter(&iter);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dax_file_unshare);
@@ -1354,17 +1354,16 @@ static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
 	return ret;
 }
 
-static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
+static int dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
 {
 	const struct iomap *iomap = &iter->iomap;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
-	loff_t pos = iter->pos;
 	u64 length = iomap_length(iter);
-	s64 written = 0;
+	int ret;
 
 	/* already zeroed?  we're done. */
 	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
-		return length;
+		return iomap_iter_advance(iter, &length);
 
 	/*
 	 * invalidate the pages whose sharing state is to be changed
@@ -1372,33 +1371,35 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
 	 */
 	if (iomap->flags & IOMAP_F_SHARED)
 		invalidate_inode_pages2_range(iter->inode->i_mapping,
-					      pos >> PAGE_SHIFT,
-					      (pos + length - 1) >> PAGE_SHIFT);
+				iter->pos >> PAGE_SHIFT,
+				(iter->pos + length - 1) >> PAGE_SHIFT);
 
 	do {
+		loff_t pos = iter->pos;
 		unsigned offset = offset_in_page(pos);
-		unsigned size = min_t(u64, PAGE_SIZE - offset, length);
 		pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
-		long rc;
 		int id;
 
+		length = min_t(u64, PAGE_SIZE - offset, length);
+
 		id = dax_read_lock();
-		if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
-			rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
+		if (IS_ALIGNED(pos, PAGE_SIZE) && length == PAGE_SIZE)
+			ret = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
 		else
-			rc = dax_memzero(iter, pos, size);
+			ret = dax_memzero(iter, pos, length);
 		dax_read_unlock(id);
 
-		if (rc < 0)
-			return rc;
-		pos += size;
-		length -= size;
-		written += size;
+		if (ret < 0)
+			return ret;
+
+		ret = iomap_iter_advance(iter, &length);
+		if (ret)
+			return ret;
 	} while (length > 0);
 
 	if (did_zero)
 		*did_zero = true;
-	return written;
+	return ret;
 }
 
 int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
@@ -1413,7 +1414,7 @@ int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 	int ret;
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = dax_zero_iter(&iter, did_zero);
+		iter.status = dax_zero_iter(&iter, did_zero);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dax_zero_range);
@@ -1431,8 +1432,7 @@ int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
 }
 EXPORT_SYMBOL_GPL(dax_truncate_page);
 
-static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
-		struct iov_iter *iter)
+static int dax_iomap_iter(struct iomap_iter *iomi, struct iov_iter *iter)
 {
 	const struct iomap *iomap = &iomi->iomap;
 	const struct iomap *srcmap = iomap_iter_srcmap(iomi);
@@ -1451,8 +1451,10 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 		if (pos >= end)
 			return 0;
 
-		if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
-			return iov_iter_zero(min(length, end - pos), iter);
+		if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN) {
+			done = iov_iter_zero(min(length, end - pos), iter);
+			return iomap_iter_advance(iomi, &done);
+		}
 	}
 
 	/*
@@ -1485,7 +1487,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 	}
 
 	id = dax_read_lock();
-	while (pos < end) {
+	while ((pos = iomi->pos) < end) {
 		unsigned offset = pos & (PAGE_SIZE - 1);
 		const size_t size = ALIGN(length + offset, PAGE_SIZE);
 		pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
@@ -1535,18 +1537,16 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 			xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr,
 					map_len, iter);
 
-		pos += xfer;
-		length -= xfer;
-		done += xfer;
-
-		if (xfer == 0)
+		length = xfer;
+		ret = iomap_iter_advance(iomi, &length);
+		if (!ret && xfer == 0)
 			ret = -EFAULT;
 		if (xfer < map_len)
 			break;
 	}
 	dax_read_unlock(id);
 
-	return done ? done : ret;
+	return ret;
 }
 
 /**
@@ -1586,7 +1586,7 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		iomi.flags |= IOMAP_NOWAIT;
 
 	while ((ret = iomap_iter(&iomi, ops)) > 0)
-		iomi.processed = dax_iomap_iter(&iomi, iter);
+		iomi.status = dax_iomap_iter(&iomi, iter);
 
 	done = iomi.pos - iocb->ki_pos;
 	iocb->ki_pos = iomi.pos;
@@ -1757,7 +1757,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 
 	while ((error = iomap_iter(&iter, ops)) > 0) {
 		if (WARN_ON_ONCE(iomap_length(&iter) < PAGE_SIZE)) {
-			iter.processed = -EIO;	/* fs corruption? */
+			iter.status = -EIO;	/* fs corruption? */
 			continue;
 		}
 
@@ -1769,8 +1769,10 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			ret |= VM_FAULT_MAJOR;
 		}
 
-		if (!(ret & VM_FAULT_ERROR))
-			iter.processed = PAGE_SIZE;
+		if (!(ret & VM_FAULT_ERROR)) {
+			u64 length = PAGE_SIZE;
+			iter.status = iomap_iter_advance(&iter, &length);
+		}
 	}
 
 	if (iomap_errp)
@@ -1883,8 +1885,10 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			continue; /* actually breaks out of the loop */
 
 		ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, true);
-		if (ret != VM_FAULT_FALLBACK)
-			iter.processed = PMD_SIZE;
+		if (ret != VM_FAULT_FALLBACK) {
+			u64 length = PMD_SIZE;
+			iter.status = iomap_iter_advance(&iter, &length);
+		}
 	}
 
 unlock_entry:
@@ -1999,12 +2003,13 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, unsigned int order,
 }
 EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
 
-static loff_t dax_range_compare_iter(struct iomap_iter *it_src,
+static int dax_range_compare_iter(struct iomap_iter *it_src,
 		struct iomap_iter *it_dest, u64 len, bool *same)
 {
 	const struct iomap *smap = &it_src->iomap;
 	const struct iomap *dmap = &it_dest->iomap;
 	loff_t pos1 = it_src->pos, pos2 = it_dest->pos;
+	u64 dest_len;
 	void *saddr, *daddr;
 	int id, ret;
 
@@ -2012,7 +2017,7 @@ static loff_t dax_range_compare_iter(struct iomap_iter *it_src,
 
 	if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE) {
 		*same = true;
-		return len;
+		goto advance;
 	}
 
 	if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
@@ -2035,7 +2040,13 @@ static loff_t dax_range_compare_iter(struct iomap_iter *it_src,
 	if (!*same)
 		len = 0;
 	dax_read_unlock(id);
-	return len;
+
+advance:
+	dest_len = len;
+	ret = iomap_iter_advance(it_src, &len);
+	if (!ret)
+		ret = iomap_iter_advance(it_dest, &dest_len);
+	return ret;
 
 out_unlock:
 	dax_read_unlock(id);
@@ -2058,15 +2069,15 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 		.len		= len,
 		.flags		= IOMAP_DAX,
 	};
-	int ret, compared = 0;
+	int ret, status;
 
 	while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
 	       (ret = iomap_iter(&dst_iter, ops)) > 0) {
-		compared = dax_range_compare_iter(&src_iter, &dst_iter,
+		status = dax_range_compare_iter(&src_iter, &dst_iter,
 				min(src_iter.len, dst_iter.len), same);
-		if (compared < 0)
+		if (status < 0)
 			return ret;
-		src_iter.processed = dst_iter.processed = compared;
+		src_iter.status = dst_iter.status = status;
 	}
 	return ret;
 }
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 8368a4ae716f..ea5e32d810d5 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -362,15 +362,14 @@ static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
 		pos >= i_size_read(iter->inode);
 }
 
-static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
-		struct iomap_readpage_ctx *ctx, loff_t offset)
+static int iomap_readpage_iter(struct iomap_iter *iter,
+		struct iomap_readpage_ctx *ctx)
 {
 	const struct iomap *iomap = &iter->iomap;
-	loff_t pos = iter->pos + offset;
-	loff_t length = iomap_length(iter) - offset;
+	loff_t pos = iter->pos;
+	loff_t length = iomap_length(iter);
 	struct folio *folio = ctx->cur_folio;
 	struct iomap_folio_state *ifs;
-	loff_t orig_pos = pos;
 	size_t poff, plen;
 	sector_t sector;
 
@@ -434,25 +433,22 @@ done:
 	 * we can skip trailing ones as they will be handled in the next
 	 * iteration.
 	 */
-	return pos - orig_pos + plen;
+	length = pos - iter->pos + plen;
+	return iomap_iter_advance(iter, &length);
 }
 
-static loff_t iomap_read_folio_iter(const struct iomap_iter *iter,
+static int iomap_read_folio_iter(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
-	struct folio *folio = ctx->cur_folio;
-	size_t offset = offset_in_folio(folio, iter->pos);
-	loff_t length = min_t(loff_t, folio_size(folio) - offset,
-			      iomap_length(iter));
-	loff_t done, ret;
-
-	for (done = 0; done < length; done += ret) {
-		ret = iomap_readpage_iter(iter, ctx, done);
-		if (ret <= 0)
+	int ret;
+
+	while (iomap_length(iter)) {
+		ret = iomap_readpage_iter(iter, ctx);
+		if (ret)
 			return ret;
 	}
 
-	return done;
+	return 0;
 }
 
 int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
@@ -470,7 +466,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 	trace_iomap_readpage(iter.inode, 1);
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_read_folio_iter(&iter, &ctx);
+		iter.status = iomap_read_folio_iter(&iter, &ctx);
 
 	if (ctx.bio) {
 		submit_bio(ctx.bio);
@@ -489,15 +485,14 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 }
 EXPORT_SYMBOL_GPL(iomap_read_folio);
 
-static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
+static int iomap_readahead_iter(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
-	loff_t length = iomap_length(iter);
-	loff_t done, ret;
+	int ret;
 
-	for (done = 0; done < length; done += ret) {
+	while (iomap_length(iter)) {
 		if (ctx->cur_folio &&
-		    offset_in_folio(ctx->cur_folio, iter->pos + done) == 0) {
+		    offset_in_folio(ctx->cur_folio, iter->pos) == 0) {
 			if (!ctx->cur_folio_in_bio)
 				folio_unlock(ctx->cur_folio);
 			ctx->cur_folio = NULL;
@@ -506,12 +501,12 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
 			ctx->cur_folio = readahead_folio(ctx->rac);
 			ctx->cur_folio_in_bio = false;
 		}
-		ret = iomap_readpage_iter(iter, ctx, done);
-		if (ret <= 0)
+		ret = iomap_readpage_iter(iter, ctx);
+		if (ret)
 			return ret;
 	}
 
-	return done;
+	return 0;
 }
 
 /**
@@ -543,7 +538,7 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
 	trace_iomap_readahead(rac->mapping->host, readahead_count(rac));
 
 	while (iomap_iter(&iter, ops) > 0)
-		iter.processed = iomap_readahead_iter(&iter, &ctx);
+		iter.status = iomap_readahead_iter(&iter, &ctx);
 
 	if (ctx.bio)
 		submit_bio(ctx.bio);
@@ -903,10 +898,10 @@ static bool iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 	return __iomap_write_end(iter->inode, pos, len, copied, folio);
 }
 
-static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
+static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 {
 	ssize_t total_written = 0;
-	long status = 0;
+	int status = 0;
 	struct address_space *mapping = iter->inode->i_mapping;
 	size_t chunk = mapping_max_folio_size(mapping);
 	unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
@@ -1026,7 +1021,7 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
 		iter.flags |= IOMAP_NOWAIT;
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_write_iter(&iter, i);
+		iter.status = iomap_write_iter(&iter, i);
 
 	if (unlikely(iter.pos == iocb->ki_pos))
 		return ret;
@@ -1260,7 +1255,7 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte,
 }
 EXPORT_SYMBOL_GPL(iomap_write_delalloc_release);
 
-static loff_t iomap_unshare_iter(struct iomap_iter *iter)
+static int iomap_unshare_iter(struct iomap_iter *iter)
 {
 	struct iomap *iomap = &iter->iomap;
 	u64 bytes = iomap_length(iter);
@@ -1320,7 +1315,7 @@ iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 
 	iter.len = min(len, size - pos);
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_unshare_iter(&iter);
+		iter.status = iomap_unshare_iter(&iter);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(iomap_file_unshare);
@@ -1339,7 +1334,7 @@ static inline int iomap_zero_iter_flush_and_stale(struct iomap_iter *i)
 	return filemap_write_and_wait_range(mapping, i->pos, end);
 }
 
-static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
+static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 {
 	u64 bytes = iomap_length(iter);
 	int status;
@@ -1413,7 +1408,7 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 	    filemap_range_needs_writeback(mapping, pos, pos + plen - 1)) {
 		iter.len = plen;
 		while ((ret = iomap_iter(&iter, ops)) > 0)
-			iter.processed = iomap_zero_iter(&iter, did_zero);
+			iter.status = iomap_zero_iter(&iter, did_zero);
 
 		iter.len = len - (iter.pos - pos);
 		if (ret || !iter.len)
@@ -1432,20 +1427,19 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 
 		if (srcmap->type == IOMAP_HOLE ||
 		    srcmap->type == IOMAP_UNWRITTEN) {
-			s64 proc;
+			s64 status;
 
 			if (range_dirty) {
 				range_dirty = false;
-				proc = iomap_zero_iter_flush_and_stale(&iter);
+				status = iomap_zero_iter_flush_and_stale(&iter);
 			} else {
-				u64 length = iomap_length(&iter);
-				proc = iomap_iter_advance(&iter, &length);
+				status = iomap_iter_advance_full(&iter);
 			}
-			iter.processed = proc;
+			iter.status = status;
 			continue;
 		}
 
-		iter.processed = iomap_zero_iter(&iter, did_zero);
+		iter.status = iomap_zero_iter(&iter, did_zero);
 	}
 	return ret;
 }
@@ -1466,7 +1460,7 @@ iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
 }
 EXPORT_SYMBOL_GPL(iomap_truncate_page);
 
-static loff_t iomap_folio_mkwrite_iter(struct iomap_iter *iter,
+static int iomap_folio_mkwrite_iter(struct iomap_iter *iter,
 		struct folio *folio)
 {
 	loff_t length = iomap_length(iter);
@@ -1483,7 +1477,7 @@ static loff_t iomap_folio_mkwrite_iter(struct iomap_iter *iter,
 		folio_mark_dirty(folio);
 	}
 
-	return length;
+	return iomap_iter_advance(iter, &length);
 }
 
 vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops,
@@ -1504,7 +1498,7 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops,
 	iter.pos = folio_pos(folio);
 	iter.len = ret;
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_folio_mkwrite_iter(&iter, folio);
+		iter.status = iomap_folio_mkwrite_iter(&iter, folio);
 
 	if (ret < 0)
 		goto out_unlock;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 138d246ec29d..e1e32e2bb0bf 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -335,8 +335,7 @@ static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
 	return opflags;
 }
 
-static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
-		struct iomap_dio *dio)
+static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
 {
 	const struct iomap *iomap = &iter->iomap;
 	struct inode *inode = iter->inode;
@@ -349,7 +348,7 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
 	bool need_zeroout = false;
 	bool use_fua = false;
 	int nr_pages, ret = 0;
-	size_t copied = 0;
+	u64 copied = 0;
 	size_t orig_count;
 
 	if (atomic && length != fs_block_size)
@@ -513,30 +512,28 @@ out:
 	/* Undo iter limitation to current extent */
 	iov_iter_reexpand(dio->submit.iter, orig_count - copied);
 	if (copied)
-		return copied;
+		return iomap_iter_advance(iter, &copied);
 	return ret;
 }
 
-static loff_t iomap_dio_hole_iter(const struct iomap_iter *iter,
-		struct iomap_dio *dio)
+static int iomap_dio_hole_iter(struct iomap_iter *iter, struct iomap_dio *dio)
 {
 	loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter);
 
 	dio->size += length;
 	if (!length)
 		return -EFAULT;
-	return length;
+	return iomap_iter_advance(iter, &length);
 }
 
-static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi,
-		struct iomap_dio *dio)
+static int iomap_dio_inline_iter(struct iomap_iter *iomi, struct iomap_dio *dio)
 {
 	const struct iomap *iomap = &iomi->iomap;
 	struct iov_iter *iter = dio->submit.iter;
 	void *inline_data = iomap_inline_data(iomap, iomi->pos);
 	loff_t length = iomap_length(iomi);
 	loff_t pos = iomi->pos;
-	size_t copied;
+	u64 copied;
 
 	if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
 		return -EIO;
@@ -558,11 +555,10 @@ static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi,
 	dio->size += copied;
 	if (!copied)
 		return -EFAULT;
-	return copied;
+	return iomap_iter_advance(iomi, &copied);
 }
 
-static loff_t iomap_dio_iter(const struct iomap_iter *iter,
-		struct iomap_dio *dio)
+static int iomap_dio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
 {
 	switch (iter->iomap.type) {
 	case IOMAP_HOLE:
@@ -746,7 +742,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 
 	blk_start_plug(&plug);
 	while ((ret = iomap_iter(&iomi, ops)) > 0) {
-		iomi.processed = iomap_dio_iter(&iomi, dio);
+		iomi.status = iomap_dio_iter(&iomi, dio);
 
 		/*
 		 * We can only poll for single bio I/Os.
diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
index 610ca6f1ec9b..80675c42e94e 100644
--- a/fs/iomap/fiemap.c
+++ b/fs/iomap/fiemap.c
@@ -39,24 +39,23 @@ static int iomap_to_fiemap(struct fiemap_extent_info *fi,
 			iomap->length, flags);
 }
 
-static loff_t iomap_fiemap_iter(const struct iomap_iter *iter,
+static int iomap_fiemap_iter(struct iomap_iter *iter,
 		struct fiemap_extent_info *fi, struct iomap *prev)
 {
 	int ret;
 
 	if (iter->iomap.type == IOMAP_HOLE)
-		return iomap_length(iter);
+		goto advance;
 
 	ret = iomap_to_fiemap(fi, prev, 0);
 	*prev = iter->iomap;
-	switch (ret) {
-	case 0:		/* success */
-		return iomap_length(iter);
-	case 1:		/* extent array full */
-		return 0;
-	default:	/* error */
+	if (ret < 0)
 		return ret;
-	}
+	if (ret == 1)	/* extent array full */
+		return 0;
+
+advance:
+	return iomap_iter_advance_full(iter);
 }
 
 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
@@ -78,7 +77,7 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
 		return ret;
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_fiemap_iter(&iter, fi, &prev);
+		iter.status = iomap_fiemap_iter(&iter, fi, &prev);
 
 	if (prev.type != IOMAP_HOLE) {
 		ret = iomap_to_fiemap(fi, &prev, FIEMAP_EXTENT_LAST);
@@ -114,7 +113,7 @@ iomap_bmap(struct address_space *mapping, sector_t bno,
 	while ((ret = iomap_iter(&iter, ops)) > 0) {
 		if (iter.iomap.type == IOMAP_MAPPED)
 			bno = iomap_sector(&iter.iomap, iter.pos) >> blkshift;
-		/* leave iter.processed unset to abort loop */
+		/* leave iter.status unset to abort loop */
 	}
 	if (ret)
 		return 0;
diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
index 0ebcabc7df52..6ffc6a7b9ba5 100644
--- a/fs/iomap/iter.c
+++ b/fs/iomap/iter.c
@@ -9,7 +9,7 @@
 
 static inline void iomap_iter_reset_iomap(struct iomap_iter *iter)
 {
-	iter->processed = 0;
+	iter->status = 0;
 	memset(&iter->iomap, 0, sizeof(iter->iomap));
 	memset(&iter->srcmap, 0, sizeof(iter->srcmap));
 }
@@ -54,15 +54,14 @@ static inline void iomap_iter_done(struct iomap_iter *iter)
  * function must be called in a loop that continues as long it returns a
  * positive value.  If 0 or a negative value is returned, the caller must not
  * return to the loop body.  Within a loop body, there are two ways to break out
- * of the loop body:  leave @iter.processed unchanged, or set it to a negative
+ * of the loop body:  leave @iter.status unchanged, or set it to a negative
  * errno.
  */
 int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
 {
 	bool stale = iter->iomap.flags & IOMAP_F_STALE;
-	ssize_t advanced = iter->processed > 0 ? iter->processed : 0;
-	u64 olen = iter->len;
-	s64 processed;
+	ssize_t advanced;
+	u64 olen;
 	int ret;
 
 	trace_iomap_iter(iter, ops, _RET_IP_);
@@ -71,14 +70,11 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
 		goto begin;
 
 	/*
-	 * If iter.processed is zero, the op may still have advanced the iter
-	 * itself. Calculate the advanced and original length bytes based on how
-	 * far pos has advanced for ->iomap_end().
+	 * Calculate how far the iter was advanced and the original length bytes
+	 * for ->iomap_end().
 	 */
-	if (!advanced) {
-		advanced = iter->pos - iter->iter_start_pos;
-		olen += advanced;
-	}
+	advanced = iter->pos - iter->iter_start_pos;
+	olen = iter->len + advanced;
 
 	if (ops->iomap_end) {
 		ret = ops->iomap_end(iter->inode, iter->iter_start_pos,
@@ -89,27 +85,22 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
 			return ret;
 	}
 
-	processed = iter->processed;
-	if (processed < 0) {
-		iomap_iter_reset_iomap(iter);
-		return processed;
-	}
+	/* detect old return semantics where this would advance */
+	if (WARN_ON_ONCE(iter->status > 0))
+		iter->status = -EIO;
 
 	/*
-	 * Advance the iter and clear state from the previous iteration. This
-	 * passes iter->processed because that reflects the bytes processed but
-	 * not yet advanced by the iter handler.
-	 *
 	 * Use iter->len to determine whether to continue onto the next mapping.
-	 * Explicitly terminate in the case where the current iter has not
+	 * Explicitly terminate on error status or if the current iter has not
 	 * advanced at all (i.e. no work was done for some reason) unless the
 	 * mapping has been marked stale and needs to be reprocessed.
 	 */
-	ret = iomap_iter_advance(iter, &processed);
-	if (!ret && iter->len > 0)
-		ret = 1;
-	if (ret > 0 && !advanced && !stale)
+	if (iter->status < 0)
+		ret = iter->status;
+	else if (iter->len == 0 || (!advanced && !stale))
 		ret = 0;
+	else
+		ret = 1;
 	iomap_iter_reset_iomap(iter);
 	if (ret <= 0)
 		return ret;
diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
index a845c012b50c..04d7919636c1 100644
--- a/fs/iomap/seek.c
+++ b/fs/iomap/seek.c
@@ -10,7 +10,7 @@
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 
-static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter,
+static int iomap_seek_hole_iter(struct iomap_iter *iter,
 		loff_t *hole_pos)
 {
 	loff_t length = iomap_length(iter);
@@ -20,13 +20,13 @@ static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter,
 		*hole_pos = mapping_seek_hole_data(iter->inode->i_mapping,
 				iter->pos, iter->pos + length, SEEK_HOLE);
 		if (*hole_pos == iter->pos + length)
-			return length;
+			return iomap_iter_advance(iter, &length);
 		return 0;
 	case IOMAP_HOLE:
 		*hole_pos = iter->pos;
 		return 0;
 	default:
-		return length;
+		return iomap_iter_advance(iter, &length);
 	}
 }
 
@@ -47,7 +47,7 @@ iomap_seek_hole(struct inode *inode, loff_t pos, const struct iomap_ops *ops)
 
 	iter.len = size - pos;
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_seek_hole_iter(&iter, &pos);
+		iter.status = iomap_seek_hole_iter(&iter, &pos);
 	if (ret < 0)
 		return ret;
 	if (iter.len) /* found hole before EOF */
@@ -56,19 +56,19 @@ iomap_seek_hole(struct inode *inode, loff_t pos, const struct iomap_ops *ops)
 }
 EXPORT_SYMBOL_GPL(iomap_seek_hole);
 
-static loff_t iomap_seek_data_iter(const struct iomap_iter *iter,
+static int iomap_seek_data_iter(struct iomap_iter *iter,
 		loff_t *hole_pos)
 {
 	loff_t length = iomap_length(iter);
 
 	switch (iter->iomap.type) {
 	case IOMAP_HOLE:
-		return length;
+		return iomap_iter_advance(iter, &length);
 	case IOMAP_UNWRITTEN:
 		*hole_pos = mapping_seek_hole_data(iter->inode->i_mapping,
 				iter->pos, iter->pos + length, SEEK_DATA);
 		if (*hole_pos < 0)
-			return length;
+			return iomap_iter_advance(iter, &length);
 		return 0;
 	default:
 		*hole_pos = iter->pos;
@@ -93,7 +93,7 @@ iomap_seek_data(struct inode *inode, loff_t pos, const struct iomap_ops *ops)
 
 	iter.len = size - pos;
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_seek_data_iter(&iter, &pos);
+		iter.status = iomap_seek_data_iter(&iter, &pos);
 	if (ret < 0)
 		return ret;
 	if (iter.len) /* found data before EOF */
diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
index b90d0eda9e51..c1a762c10ce4 100644
--- a/fs/iomap/swapfile.c
+++ b/fs/iomap/swapfile.c
@@ -94,7 +94,7 @@ static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
  * swap only cares about contiguous page-aligned physical extents and makes no
  * distinction between written and unwritten extents.
  */
-static loff_t iomap_swapfile_iter(const struct iomap_iter *iter,
+static int iomap_swapfile_iter(struct iomap_iter *iter,
 		struct iomap *iomap, struct iomap_swapfile_info *isi)
 {
 	switch (iomap->type) {
@@ -132,7 +132,8 @@ static loff_t iomap_swapfile_iter(const struct iomap_iter *iter,
 			return error;
 		memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 	}
-	return iomap_length(iter);
+
+	return iomap_iter_advance_full(iter);
 }
 
 /*
@@ -166,7 +167,7 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
 		return ret;
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.processed = iomap_swapfile_iter(&iter, &iter.iomap, &isi);
+		iter.status = iomap_swapfile_iter(&iter, &iter.iomap, &isi);
 	if (ret < 0)
 		return ret;
 
diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h
index 4118a42cdab0..9eab2c8ac3c5 100644
--- a/fs/iomap/trace.h
+++ b/fs/iomap/trace.h
@@ -207,7 +207,7 @@ TRACE_EVENT(iomap_iter,
 		__field(u64, ino)
 		__field(loff_t, pos)
 		__field(u64, length)
-		__field(s64, processed)
+		__field(int, status)
 		__field(unsigned int, flags)
 		__field(const void *, ops)
 		__field(unsigned long, caller)
@@ -217,17 +217,17 @@ TRACE_EVENT(iomap_iter,
 		__entry->ino = iter->inode->i_ino;
 		__entry->pos = iter->pos;
 		__entry->length = iomap_length(iter);
-		__entry->processed = iter->processed;
+		__entry->status = iter->status;
 		__entry->flags = iter->flags;
 		__entry->ops = ops;
 		__entry->caller = caller;
 	),
-	TP_printk("dev %d:%d ino 0x%llx pos 0x%llx length 0x%llx processed %lld flags %s (0x%x) ops %ps caller %pS",
+	TP_printk("dev %d:%d ino 0x%llx pos 0x%llx length 0x%llx status %d flags %s (0x%x) ops %ps caller %pS",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		   __entry->ino,
 		   __entry->pos,
 		   __entry->length,
-		   __entry->processed,
+		   __entry->status,
 		   __print_flags(__entry->flags, "|", IOMAP_FLAGS_STRINGS),
 		   __entry->flags,
 		   __entry->ops,
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index e180dacf434c..1fd66bc29cc1 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -220,9 +220,8 @@ struct iomap_ops {
  *	It is updated at the same time as @pos.
  * @iter_start_pos: The original start pos for the current iomap. Used for
  *	incremental iter advance.
- * @processed: The number of bytes the most recent iteration needs iomap_iter()
- *	to advance the iter, zero if the iter was already advanced, or a
- *	negative errno for an error during the operation.
+ * @status: Status of the most recent iteration. Zero on success or a negative
+ *	errno on error.
  * @flags: Zero or more of the iomap_begin flags above.
  * @iomap: Map describing the I/O iteration
  * @srcmap: Source map for COW operations
@@ -232,7 +231,7 @@ struct iomap_iter {
 	loff_t pos;
 	u64 len;
 	loff_t iter_start_pos;
-	s64 processed;
+	int status;
 	unsigned flags;
 	struct iomap iomap;
 	struct iomap srcmap;
@@ -273,6 +272,16 @@ static inline u64 iomap_length(const struct iomap_iter *iter)
 }
 
 /**
+ * iomap_iter_advance_full - advance by the full length of current map
+ */
+static inline int iomap_iter_advance_full(struct iomap_iter *iter)
+{
+	u64 length = iomap_length(iter);
+
+	return iomap_iter_advance(iter, &length);
+}
+
+/**
  * iomap_iter_srcmap - return the source map for the current iomap iteration
  * @i: iteration structure
  *