[PATCH v2 0/6] iomap: misc buffered write path cleanups and prep

[PATCH v2 0/6] iomap: misc buffered write path cleanups and prep

[Brian Foster]

Hi all,

Here's a bit more fallout and prep. work associated with the folio batch
prototype posted a while back [1]. Work on that is still pending so it
isn't included here, but based on the iter advance cleanups most of
these seemed worthwhile as standalone cleanups. Mainly this just cleans
up some of the helpers and pushes some pos/len trimming further down in
the write begin path.

The fbatch thing is still in prototype stage, but for context the intent
here is that it can mostly now just bolt onto the folio lookup path
because we can advance the range that is skipped and return the next
folio along with the folio subrange for the caller to process.

Thoughts, reviews, flames appreciated.

Brian

[1] https://lore.kernel.org/linux-fsdevel/20241213150528.1003662-1-bfoster@redhat.com/

v2:
- Split up warning in trim folio range helper.
- Use min() and min_not_zero() instead of open coding.
- Drop pos param from __iomap_write_begin() (folded into patch 6).
v1: https://lore.kernel.org/linux-fsdevel/20250430190112.690800-1-bfoster@redhat.com/

Brian Foster (6):
  iomap: resample iter->pos after iomap_write_begin() calls
  iomap: drop unnecessary pos param from iomap_write_[begin|end]
  iomap: drop pos param from __iomap_[get|put]_folio()
  iomap: helper to trim pos/bytes to within folio
  iomap: push non-large folio check into get folio path
  iomap: rework iomap_write_begin() to return folio offset and length

 fs/iomap/buffered-io.c | 100 ++++++++++++++++++++++++-----------------
 1 file changed, 58 insertions(+), 42 deletions(-)

-- 
2.49.0

[PATCH v2 1/6] iomap: resample iter->pos after iomap_write_begin() calls

[Brian Foster]

In preparation for removing the pos parameter, push the local pos
assignment down after calls to iomap_write_begin().

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 5b08bd417b28..a41c8ffc4996 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -920,11 +920,11 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		size_t bytes;		/* Bytes to write to folio */
 		size_t copied;		/* Bytes copied from user */
 		u64 written;		/* Bytes have been written */
-		loff_t pos = iter->pos;
+		loff_t pos;
 
 		bytes = iov_iter_count(i);
 retry:
-		offset = pos & (chunk - 1);
+		offset = iter->pos & (chunk - 1);
 		bytes = min(chunk - offset, bytes);
 		status = balance_dirty_pages_ratelimited_flags(mapping,
 							       bdp_flags);
@@ -949,13 +949,14 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			break;
 		}
 
-		status = iomap_write_begin(iter, pos, bytes, &folio);
+		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
 		if (unlikely(status)) {
-			iomap_write_failed(iter->inode, pos, bytes);
+			iomap_write_failed(iter->inode, iter->pos, bytes);
 			break;
 		}
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
+		pos = iter->pos;
 
 		offset = offset_in_folio(folio, pos);
 		if (bytes > folio_size(folio) - offset)
@@ -1276,15 +1277,16 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 	do {
 		struct folio *folio;
 		size_t offset;
-		loff_t pos = iter->pos;
+		loff_t pos;
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, pos, bytes, &folio);
+		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
 		if (unlikely(status))
 			return status;
 		if (iomap->flags & IOMAP_F_STALE)
 			break;
+		pos = iter->pos;
 
 		offset = offset_in_folio(folio, pos);
 		if (bytes > folio_size(folio) - offset)
@@ -1351,15 +1353,16 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 	do {
 		struct folio *folio;
 		size_t offset;
-		loff_t pos = iter->pos;
+		loff_t pos;
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, pos, bytes, &folio);
+		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
 		if (status)
 			return status;
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
+		pos = iter->pos;
 
 		/* warn about zeroing folios beyond eof that won't write back */
 		WARN_ON_ONCE(folio_pos(folio) > iter->inode->i_size);
-- 
2.49.0

[PATCH v2 2/6] iomap: drop unnecessary pos param from iomap_write_[begin|end]

[Brian Foster]

iomap_write_begin() and iomap_write_end() both take the iter and
iter->pos as parameters. Drop the unnecessary pos parameter and
sample iter->pos within each function.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index a41c8ffc4996..d1a50300a5dc 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -774,11 +774,12 @@ static int iomap_write_begin_inline(const struct iomap_iter *iter,
 	return iomap_read_inline_data(iter, folio);
 }
 
-static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
-		size_t len, struct folio **foliop)
+static int iomap_write_begin(struct iomap_iter *iter, size_t len,
+		struct folio **foliop)
 {
 	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
+	loff_t pos = iter->pos;
 	struct folio *folio;
 	int status = 0;
 
@@ -883,10 +884,11 @@ static void iomap_write_end_inline(const struct iomap_iter *iter,
  * Returns true if all copied bytes have been written to the pagecache,
  * otherwise return false.
  */
-static bool iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
-		size_t copied, struct folio *folio)
+static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
+		struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
+	loff_t pos = iter->pos;
 
 	if (srcmap->type == IOMAP_INLINE) {
 		iomap_write_end_inline(iter, folio, pos, copied);
@@ -949,7 +951,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			break;
 		}
 
-		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
+		status = iomap_write_begin(iter, bytes, &folio);
 		if (unlikely(status)) {
 			iomap_write_failed(iter->inode, iter->pos, bytes);
 			break;
@@ -966,7 +968,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			flush_dcache_folio(folio);
 
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
-		written = iomap_write_end(iter, pos, bytes, copied, folio) ?
+		written = iomap_write_end(iter, bytes, copied, folio) ?
 			  copied : 0;
 
 		/*
@@ -1281,7 +1283,7 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
+		status = iomap_write_begin(iter, bytes, &folio);
 		if (unlikely(status))
 			return status;
 		if (iomap->flags & IOMAP_F_STALE)
@@ -1292,7 +1294,7 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 		if (bytes > folio_size(folio) - offset)
 			bytes = folio_size(folio) - offset;
 
-		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(!ret))
 			return -EIO;
@@ -1357,7 +1359,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, iter->pos, bytes, &folio);
+		status = iomap_write_begin(iter, bytes, &folio);
 		if (status)
 			return status;
 		if (iter->iomap.flags & IOMAP_F_STALE)
@@ -1373,7 +1375,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_zero_range(folio, offset, bytes);
 		folio_mark_accessed(folio);
 
-		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(!ret))
 			return -EIO;
-- 
2.49.0

[PATCH v2 3/6] iomap: drop pos param from __iomap_[get|put]_folio()

[Brian Foster]

Both helpers take the iter and pos as parameters. All callers
effectively pass iter->pos, so drop the unnecessary pos parameter.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d1a50300a5dc..5c08b2916bc7 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -741,10 +741,10 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 	return 0;
 }
 
-static struct folio *__iomap_get_folio(struct iomap_iter *iter, loff_t pos,
-		size_t len)
+static struct folio *__iomap_get_folio(struct iomap_iter *iter, size_t len)
 {
 	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
+	loff_t pos = iter->pos;
 
 	if (folio_ops && folio_ops->get_folio)
 		return folio_ops->get_folio(iter, pos, len);
@@ -752,10 +752,11 @@ static struct folio *__iomap_get_folio(struct iomap_iter *iter, loff_t pos,
 		return iomap_get_folio(iter, pos, len);
 }
 
-static void __iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret,
+static void __iomap_put_folio(struct iomap_iter *iter, size_t ret,
 		struct folio *folio)
 {
 	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
+	loff_t pos = iter->pos;
 
 	if (folio_ops && folio_ops->put_folio) {
 		folio_ops->put_folio(iter->inode, pos, ret, folio);
@@ -793,7 +794,7 @@ static int iomap_write_begin(struct iomap_iter *iter, size_t len,
 	if (!mapping_large_folio_support(iter->inode->i_mapping))
 		len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
 
-	folio = __iomap_get_folio(iter, pos, len);
+	folio = __iomap_get_folio(iter, len);
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
 
@@ -834,7 +835,7 @@ static int iomap_write_begin(struct iomap_iter *iter, size_t len,
 	return 0;
 
 out_unlock:
-	__iomap_put_folio(iter, pos, 0, folio);
+	__iomap_put_folio(iter, 0, folio);
 
 	return status;
 }
@@ -983,7 +984,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			i_size_write(iter->inode, pos + written);
 			iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
 		}
-		__iomap_put_folio(iter, pos, written, folio);
+		__iomap_put_folio(iter, written, folio);
 
 		if (old_size < pos)
 			pagecache_isize_extended(iter->inode, old_size, pos);
@@ -1295,7 +1296,7 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 			bytes = folio_size(folio) - offset;
 
 		ret = iomap_write_end(iter, bytes, bytes, folio);
-		__iomap_put_folio(iter, pos, bytes, folio);
+		__iomap_put_folio(iter, bytes, folio);
 		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
@@ -1376,7 +1377,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_mark_accessed(folio);
 
 		ret = iomap_write_end(iter, bytes, bytes, folio);
-		__iomap_put_folio(iter, pos, bytes, folio);
+		__iomap_put_folio(iter, bytes, folio);
 		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
-- 
2.49.0

[PATCH v2 4/6] iomap: helper to trim pos/bytes to within folio

[Brian Foster]

Several buffered write based iteration callbacks duplicate logic to
trim the current pos and length to within the current folio. Factor
this into a helper to make it easier to relocate closer to folio
lookup.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 5c08b2916bc7..11046a3c60fe 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -766,6 +766,22 @@ static void __iomap_put_folio(struct iomap_iter *iter, size_t ret,
 	}
 }
 
+/* trim pos and bytes to within a given folio */
+static loff_t iomap_trim_folio_range(struct iomap_iter *iter,
+		struct folio *folio, size_t *offset, u64 *bytes)
+{
+	loff_t pos = iter->pos;
+	size_t fsize = folio_size(folio);
+
+	WARN_ON_ONCE(pos < folio_pos(folio));
+	WARN_ON_ONCE(pos >= folio_pos(folio) + fsize);
+
+	*offset = offset_in_folio(folio, pos);
+	*bytes = min(*bytes, fsize - *offset);
+
+	return pos;
+}
+
 static int iomap_write_begin_inline(const struct iomap_iter *iter,
 		struct folio *folio)
 {
@@ -920,7 +936,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		struct folio *folio;
 		loff_t old_size;
 		size_t offset;		/* Offset into folio */
-		size_t bytes;		/* Bytes to write to folio */
+		u64 bytes;		/* Bytes to write to folio */
 		size_t copied;		/* Bytes copied from user */
 		u64 written;		/* Bytes have been written */
 		loff_t pos;
@@ -959,11 +975,8 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		}
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
-		pos = iter->pos;
 
-		offset = offset_in_folio(folio, pos);
-		if (bytes > folio_size(folio) - offset)
-			bytes = folio_size(folio) - offset;
+		pos = iomap_trim_folio_range(iter, folio, &offset, &bytes);
 
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_folio(folio);
@@ -1280,7 +1293,6 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 	do {
 		struct folio *folio;
 		size_t offset;
-		loff_t pos;
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
@@ -1289,11 +1301,8 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 			return status;
 		if (iomap->flags & IOMAP_F_STALE)
 			break;
-		pos = iter->pos;
 
-		offset = offset_in_folio(folio, pos);
-		if (bytes > folio_size(folio) - offset)
-			bytes = folio_size(folio) - offset;
+		iomap_trim_folio_range(iter, folio, &offset, &bytes);
 
 		ret = iomap_write_end(iter, bytes, bytes, folio);
 		__iomap_put_folio(iter, bytes, folio);
@@ -1356,7 +1365,6 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 	do {
 		struct folio *folio;
 		size_t offset;
-		loff_t pos;
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
@@ -1365,14 +1373,11 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 			return status;
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
-		pos = iter->pos;
 
 		/* warn about zeroing folios beyond eof that won't write back */
 		WARN_ON_ONCE(folio_pos(folio) > iter->inode->i_size);
-		offset = offset_in_folio(folio, pos);
-		if (bytes > folio_size(folio) - offset)
-			bytes = folio_size(folio) - offset;
 
+		iomap_trim_folio_range(iter, folio, &offset, &bytes);
 		folio_zero_range(folio, offset, bytes);
 		folio_mark_accessed(folio);
 
-- 
2.49.0

[PATCH v2 5/6] iomap: push non-large folio check into get folio path

[Brian Foster]

The len param to __iomap_get_folio() is primarily a folio allocation
hint. iomap_write_begin() already trims its local len variable based
on the provided folio, so move the large folio support check closer
to folio lookup.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 11046a3c60fe..92d7b659db33 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -746,6 +746,9 @@ static struct folio *__iomap_get_folio(struct iomap_iter *iter, size_t len)
 	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
 	loff_t pos = iter->pos;
 
+	if (!mapping_large_folio_support(iter->inode->i_mapping))
+		len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
+
 	if (folio_ops && folio_ops->get_folio)
 		return folio_ops->get_folio(iter, pos, len);
 	else
@@ -807,9 +810,6 @@ static int iomap_write_begin(struct iomap_iter *iter, size_t len,
 	if (fatal_signal_pending(current))
 		return -EINTR;
 
-	if (!mapping_large_folio_support(iter->inode->i_mapping))
-		len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
-
 	folio = __iomap_get_folio(iter, len);
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
-- 
2.49.0

[PATCH v2 6/6] iomap: rework iomap_write_begin() to return folio offset and length

[Brian Foster]

iomap_write_begin() returns a folio based on current pos and
remaining length in the iter, and each caller then trims the
pos/length to the given folio. Clean this up a bit and let
iomap_write_begin() return the trimmed range along with the folio.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/buffered-io.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 92d7b659db33..233abf598f65 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -679,11 +679,12 @@ static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
 	return submit_bio_wait(&bio);
 }
 
-static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
-		size_t len, struct folio *folio)
+static int __iomap_write_begin(const struct iomap_iter *iter, size_t len,
+		struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	struct iomap_folio_state *ifs;
+	loff_t pos = iter->pos;
 	loff_t block_size = i_blocksize(iter->inode);
 	loff_t block_start = round_down(pos, block_size);
 	loff_t block_end = round_up(pos + len, block_size);
@@ -794,15 +795,22 @@ static int iomap_write_begin_inline(const struct iomap_iter *iter,
 	return iomap_read_inline_data(iter, folio);
 }
 
-static int iomap_write_begin(struct iomap_iter *iter, size_t len,
-		struct folio **foliop)
+/*
+ * Grab and prepare a folio for write based on iter state. Returns the folio,
+ * offset, and length. Callers can optionally pass a max length *plen,
+ * otherwise init to zero.
+ */
+static int iomap_write_begin(struct iomap_iter *iter, struct folio **foliop,
+		size_t *poffset, u64 *plen)
 {
 	const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t pos = iter->pos;
+	u64 len = min_t(u64, SIZE_MAX, iomap_length(iter));
 	struct folio *folio;
 	int status = 0;
 
+	len = min_not_zero(len, *plen);
 	BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
 	if (srcmap != &iter->iomap)
 		BUG_ON(pos + len > srcmap->offset + srcmap->length);
@@ -834,20 +842,20 @@ static int iomap_write_begin(struct iomap_iter *iter, size_t len,
 		}
 	}
 
-	if (pos + len > folio_pos(folio) + folio_size(folio))
-		len = folio_pos(folio) + folio_size(folio) - pos;
+	pos = iomap_trim_folio_range(iter, folio, poffset, &len);
 
 	if (srcmap->type == IOMAP_INLINE)
 		status = iomap_write_begin_inline(iter, folio);
 	else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
 		status = __block_write_begin_int(folio, pos, len, NULL, srcmap);
 	else
-		status = __iomap_write_begin(iter, pos, len, folio);
+		status = __iomap_write_begin(iter, len, folio);
 
 	if (unlikely(status))
 		goto out_unlock;
 
 	*foliop = folio;
+	*plen = len;
 	return 0;
 
 out_unlock:
@@ -968,7 +976,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			break;
 		}
 
-		status = iomap_write_begin(iter, bytes, &folio);
+		status = iomap_write_begin(iter, &folio, &offset, &bytes);
 		if (unlikely(status)) {
 			iomap_write_failed(iter->inode, iter->pos, bytes);
 			break;
@@ -976,7 +984,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		if (iter->iomap.flags & IOMAP_F_STALE)
 			break;
 
-		pos = iomap_trim_folio_range(iter, folio, &offset, &bytes);
+		pos = iter->pos;
 
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_folio(folio);
@@ -1296,14 +1304,12 @@ static int iomap_unshare_iter(struct iomap_iter *iter)
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, bytes, &folio);
+		status = iomap_write_begin(iter, &folio, &offset, &bytes);
 		if (unlikely(status))
 			return status;
 		if (iomap->flags & IOMAP_F_STALE)
 			break;
 
-		iomap_trim_folio_range(iter, folio, &offset, &bytes);
-
 		ret = iomap_write_end(iter, bytes, bytes, folio);
 		__iomap_put_folio(iter, bytes, folio);
 		if (WARN_ON_ONCE(!ret))
@@ -1368,7 +1374,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		bool ret;
 
 		bytes = min_t(u64, SIZE_MAX, bytes);
-		status = iomap_write_begin(iter, bytes, &folio);
+		status = iomap_write_begin(iter, &folio, &offset, &bytes);
 		if (status)
 			return status;
 		if (iter->iomap.flags & IOMAP_F_STALE)
@@ -1377,7 +1383,6 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		/* warn about zeroing folios beyond eof that won't write back */
 		WARN_ON_ONCE(folio_pos(folio) > iter->inode->i_size);
 
-		iomap_trim_folio_range(iter, folio, &offset, &bytes);
 		folio_zero_range(folio, offset, bytes);
 		folio_mark_accessed(folio);
 
-- 
2.49.0

Re: [PATCH v2 0/6] iomap: misc buffered write path cleanups and prep

[Christian Brauner]

On Tue, 06 May 2025 09:41:12 -0400, Brian Foster wrote:
> Here's a bit more fallout and prep. work associated with the folio batch
> prototype posted a while back [1]. Work on that is still pending so it
> isn't included here, but based on the iter advance cleanups most of
> these seemed worthwhile as standalone cleanups. Mainly this just cleans
> up some of the helpers and pushes some pos/len trimming further down in
> the write begin path.
> 
> [...]

Applied to the vfs-6.16.iomap branch of the vfs/vfs.git tree.
Patches in the vfs-6.16.iomap branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.16.iomap

[1/6] iomap: resample iter->pos after iomap_write_begin() calls
      https://git.kernel.org/vfs/vfs/c/e356c5d5b10e
[2/6] iomap: drop unnecessary pos param from iomap_write_[begin|end]
      https://git.kernel.org/vfs/vfs/c/99fe6e61fd3c
[3/6] iomap: drop pos param from __iomap_[get|put]_folio()
      https://git.kernel.org/vfs/vfs/c/3ceb65b17676
[4/6] iomap: helper to trim pos/bytes to within folio
      https://git.kernel.org/vfs/vfs/c/c4f9a1ba747d
[5/6] iomap: push non-large folio check into get folio path
      https://git.kernel.org/vfs/vfs/c/c0f8658a9dbc
[6/6] iomap: rework iomap_write_begin() to return folio offset and length
      https://git.kernel.org/vfs/vfs/c/66c0d8551428