[PATCH 0/5] exfat: convert to iomap

[PATCH 0/5] exfat: convert to iomap

[Namjae Jeon]

This patch series converts the exfat filesystem to the iomap framework for
buffered I/O, direct I/O, and llseek (SEEK_HOLE/SEEK_DATA) support.

Namjae Jeon (5):
  exfat: add iomap support
  exfat: add iomap direct I/O support
  exfat: add iomap buffered I/O support
  exfat: add support for multi-cluster allocation
  exfat: add support for SEEK_HOLE and SEEK_DATA in llseek

 fs/exfat/Makefile   |   2 +-
 fs/exfat/dir.c      |   2 +-
 fs/exfat/exfat_fs.h |  17 ++-
 fs/exfat/fatent.c   |  26 ++--
 fs/exfat/file.c     | 243 ++++++++++++++++++++++---------
 fs/exfat/inode.c    | 341 +++++---------------------------------------
 fs/exfat/iomap.c    | 305 +++++++++++++++++++++++++++++++++++++++
 fs/exfat/iomap.h    |  16 +++
 fs/exfat/namei.c    |   2 +-
 fs/exfat/super.c    |   1 +
 10 files changed, 565 insertions(+), 390 deletions(-)
 create mode 100644 fs/exfat/iomap.c
 create mode 100644 fs/exfat/iomap.h

-- 
2.25.1

[PATCH 1/5] exfat: add iomap support

[Namjae Jeon]

Add iomap support to the exfat filesystem. This patch introduces the
necessary iomap infrastructure by adding a new iomap.c file and related
iomap operations. The main change is converting exfat_extend_valid_size()
to use iomap_zero_range() instead of the legacy write_begin/write_end path.
To support this, exfat_map_cluster() is extended to return whether a new
cluster was allocated via a balloc flag, and a new helper function
exfat_cluster_to_phys() is added. Also, data_start_bytes is added to
struct exfat_sb_info for easier conversion from cluster number to physical
byte offset.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/Makefile   |   2 +-
 fs/exfat/exfat_fs.h |  12 ++
 fs/exfat/file.c     |  54 +++-----
 fs/exfat/inode.c    |   9 +-
 fs/exfat/iomap.c    | 305 ++++++++++++++++++++++++++++++++++++++++++++
 fs/exfat/iomap.h    |  16 +++
 fs/exfat/super.c    |   1 +
 7 files changed, 361 insertions(+), 38 deletions(-)
 create mode 100644 fs/exfat/iomap.c
 create mode 100644 fs/exfat/iomap.h

diff --git a/fs/exfat/Makefile b/fs/exfat/Makefile
index ed51926a4971..e06bf85870ae 100644
--- a/fs/exfat/Makefile
+++ b/fs/exfat/Makefile
@@ -5,4 +5,4 @@
 obj-$(CONFIG_EXFAT_FS) += exfat.o
 
 exfat-y	:= inode.o namei.o dir.o super.o fatent.o cache.o nls.o misc.o \
-	   file.o balloc.o
+	   file.o balloc.o iomap.o
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 9fed9fb33cae..860f2e438b63 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -259,6 +259,7 @@ struct exfat_sb_info {
 	unsigned long long FAT1_start_sector; /* FAT1 start sector */
 	unsigned long long FAT2_start_sector; /* FAT2 start sector */
 	unsigned long long data_start_sector; /* data area start sector */
+	unsigned long long data_start_bytes;
 	unsigned int num_FAT_sectors; /* num of FAT sectors */
 	unsigned int root_dir; /* root dir cluster */
 	unsigned int dentries_per_clu; /* num of dentries per cluster */
@@ -432,6 +433,13 @@ static inline loff_t exfat_ondisk_size(const struct inode *inode)
 	return ((loff_t)inode->i_blocks) << 9;
 }
 
+static inline loff_t exfat_cluster_to_phys(struct exfat_sb_info *sbi,
+		unsigned int clus)
+{
+	return ((loff_t)(clus - EXFAT_RESERVED_CLUSTERS) << sbi->cluster_size_bits) +
+		sbi->data_start_bytes;
+}
+
 /* super.c */
 int exfat_set_volume_dirty(struct super_block *sb);
 int exfat_clear_volume_dirty(struct super_block *sb);
@@ -480,6 +488,7 @@ long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
 long exfat_compat_ioctl(struct file *filp, unsigned int cmd,
 				unsigned long arg);
 int exfat_force_shutdown(struct super_block *sb, u32 flags);
+int exfat_extend_valid_size(struct inode *inode, loff_t off, bool bsync);
 
 /* namei.c */
 extern const struct dentry_operations exfat_dentry_ops;
@@ -543,6 +552,9 @@ int __exfat_write_inode(struct inode *inode, int sync);
 int exfat_write_inode(struct inode *inode, struct writeback_control *wbc);
 void exfat_evict_inode(struct inode *inode);
 int exfat_block_truncate_page(struct inode *inode, loff_t from);
+int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
+		unsigned int *clu, unsigned int *count, int create,
+		bool *balloc);
 
 /* exfat/nls.c */
 unsigned short exfat_toupper(struct super_block *sb, unsigned short a);
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 2daf0dbabb24..756846b774c4 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -14,9 +14,11 @@
 #include <linux/writeback.h>
 #include <linux/filelock.h>
 #include <linux/falloc.h>
+#include <linux/iomap.h>
 
 #include "exfat_raw.h"
 #include "exfat_fs.h"
+#include "iomap.h"
 
 static int exfat_cont_expand(struct inode *inode, loff_t size)
 {
@@ -628,44 +630,28 @@ int exfat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	return blkdev_issue_flush(inode->i_sb->s_bdev);
 }
 
-static int exfat_extend_valid_size(struct inode *inode, loff_t new_valid_size)
+int exfat_extend_valid_size(struct inode *inode, loff_t off, bool bsync)
 {
-	int err;
-	loff_t pos;
 	struct exfat_inode_info *ei = EXFAT_I(inode);
-	struct address_space *mapping = inode->i_mapping;
-	const struct address_space_operations *ops = mapping->a_ops;
-
-	pos = ei->valid_size;
-	while (pos < new_valid_size) {
-		u32 len;
-		struct folio *folio;
-		unsigned long off;
-
-		len = PAGE_SIZE - (pos & (PAGE_SIZE - 1));
-		if (pos + len > new_valid_size)
-			len = new_valid_size - pos;
-
-		err = ops->write_begin(NULL, mapping, pos, len, &folio, NULL);
-		if (err)
-			goto out;
-
-		off = offset_in_folio(folio, pos);
-		folio_zero_new_buffers(folio, off, off + len);
+	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
+	loff_t old_valid_size;
+	int ret = 0;
 
-		err = ops->write_end(NULL, mapping, pos, len, len, folio, NULL);
-		if (err < 0)
-			goto out;
-		pos += len;
+	mutex_lock(&sbi->s_lock);
+	old_valid_size = ei->valid_size;
+	mutex_unlock(&sbi->s_lock);
 
-		balance_dirty_pages_ratelimited(mapping);
-		cond_resched();
+	if (old_valid_size < off) {
+		ret = iomap_zero_range(inode, old_valid_size,
+				off - old_valid_size, NULL,
+				&exfat_write_iomap_ops, &exfat_iomap_folio_ops,
+				NULL);
+		if (!ret && bsync)
+			ret = filemap_write_and_wait_range(inode->i_mapping,
+					old_valid_size, off - 1);
 	}
 
-	return 0;
-
-out:
-	return err;
+	return ret;
 }
 
 static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
@@ -702,7 +688,7 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	}
 
 	if (pos > valid_size) {
-		ret = exfat_extend_valid_size(inode, pos);
+		ret = exfat_extend_valid_size(inode, pos, false);
 		if (ret < 0 && ret != -ENOSPC) {
 			exfat_err(inode->i_sb,
 				"write: fail to zero from %llu to %llu(%zd)",
@@ -760,7 +746,7 @@ static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)
 	new_valid_size = min(new_valid_size, i_size_read(inode));
 
 	if (ei->valid_size < new_valid_size) {
-		err = exfat_extend_valid_size(inode, new_valid_size);
+		err = exfat_extend_valid_size(inode, new_valid_size, false);
 		if (err < 0) {
 			inode_unlock(inode);
 			return vmf_fs_error(err);
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index beb9ea7cca9f..cc54cce65a31 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -123,8 +123,9 @@ void exfat_sync_inode(struct inode *inode)
  * Output: errcode, cluster number
  * *clu = (~0), if it's unable to allocate a new cluster
  */
-static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
-		unsigned int *clu, unsigned int *count, int create)
+int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
+		unsigned int *clu, unsigned int *count, int create,
+		bool *balloc)
 {
 	int ret;
 	unsigned int last_clu;
@@ -235,6 +236,7 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 			}
 		}
 		*count = 1;
+		*balloc = true;
 	}
 
 	/* hint information */
@@ -258,6 +260,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 	sector_t phys = 0;
 	sector_t valid_blks;
 	loff_t i_size;
+	bool balloc;
 
 	mutex_lock(&sbi->s_lock);
 	i_size = i_size_read(inode);
@@ -268,7 +271,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 	/* Is this block already allocated? */
 	count = EXFAT_B_TO_CLU_ROUND_UP(bh_result->b_size, sbi);
 	err = exfat_map_cluster(inode, iblock >> sbi->sect_per_clus_bits,
-			&cluster, &count, create);
+			&cluster, &count, create, &balloc);
 	if (err) {
 		if (err != -ENOSPC)
 			exfat_fs_error_ratelimit(sb,
diff --git a/fs/exfat/iomap.c b/fs/exfat/iomap.c
new file mode 100644
index 000000000000..e4135a13454f
--- /dev/null
+++ b/fs/exfat/iomap.c
@@ -0,0 +1,305 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * iomap callack functions
+ *
+ * Copyright (C) 2026 Namjae Jeon <linkinjeon@kernel.org>
+ */
+
+#include <linux/iomap.h>
+#include <linux/pagemap.h>
+
+#include "exfat_raw.h"
+#include "exfat_fs.h"
+#include "iomap.h"
+
+/*
+ * exfat_iomap_put_folio - Put folio after iomap operation
+ *
+ * Called when iomap is finished with a folio zero-fills portions of
+ * the folio beyond ->valid_size to prevent exposing uninitialized data.
+ */
+static void exfat_iomap_put_folio(struct inode *inode, loff_t pos,
+		unsigned int len, struct folio *folio)
+{
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
+	unsigned long sector_size = 1UL << inode->i_blkbits;
+	loff_t start_down, end_up, init;
+
+	mutex_lock(&sbi->s_lock);
+	start_down = round_down(pos, sector_size);
+	end_up = (pos + len - 1) | (sector_size - 1);
+	init = ei->valid_size;
+
+	if (init >= start_down && init <= end_up) {
+		if (init < pos) {
+			loff_t offset = offset_in_folio(folio, pos + len);
+
+			if (offset == 0)
+				offset = folio_size(folio);
+			folio_zero_segments(folio,
+					offset_in_folio(folio, init),
+					offset_in_folio(folio, pos),
+					offset,
+					folio_size(folio));
+
+		} else  {
+			loff_t offset = max_t(loff_t, pos + len, init);
+
+			offset = offset_in_folio(folio, offset);
+			if (offset == 0)
+				offset = folio_size(folio);
+			folio_zero_segment(folio,
+					offset,
+					folio_size(folio));
+		}
+	} else if (init <= pos) {
+		loff_t offset = 0, offset2 = offset_in_folio(folio, pos + len);
+
+		if ((init >> folio_shift(folio)) == (pos >> folio_shift(folio)))
+			offset = offset_in_folio(folio, init);
+		if (offset2 == 0)
+			offset2 = folio_size(folio);
+		folio_zero_segments(folio,
+				offset,
+				offset_in_folio(folio, pos),
+				offset2,
+				folio_size(folio));
+	}
+
+	folio_unlock(folio);
+	folio_put(folio);
+	mutex_unlock(&sbi->s_lock);
+}
+
+const struct iomap_write_ops exfat_iomap_folio_ops = {
+	.put_folio = exfat_iomap_put_folio,
+};
+
+/*
+ * exfat_file_write_dio_end_io - Direct I/O write completion handler
+ *
+ * Updates i_size if the write extended the file. Called from the dio layer
+ * after I/O completion.
+ */
+static int exfat_file_write_dio_end_io(struct kiocb *iocb, ssize_t size,
+		int error, unsigned int flags)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	if (error)
+		return error;
+
+	if (size && i_size_read(inode) < iocb->ki_pos + size) {
+		i_size_write(inode, iocb->ki_pos + size);
+		mark_inode_dirty(inode);
+	}
+
+	return 0;
+}
+
+const struct iomap_dio_ops exfat_write_dio_ops = {
+	.end_io		= exfat_file_write_dio_end_io,
+};
+
+/*
+ * exfat_read_iomap_begin - Begin mapping for reads
+ *
+ * Maps file range to disk location for read operations (read folio,
+ * readahead, direct I/O read, etc.).
+ *
+ * Returns IOMAP_MAPPED for areas within ->valid_size, and IOMAP_UNWRITTEN
+ * for allocated but uninitialized regions beyond ->valid_size.
+ */
+static int exfat_read_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
+		unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
+{
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	unsigned int cluster, num_clusters = EXFAT_B_TO_CLU_ROUND_UP(length, sbi);
+	loff_t cluster_offset, cluster_length;
+	int err = 0;
+	bool balloc = false;
+
+	mutex_lock(&sbi->s_lock);
+	iomap->bdev = inode->i_sb->s_bdev;
+	iomap->offset = offset;
+
+	err = exfat_map_cluster(inode, EXFAT_B_TO_CLU(offset, sbi),
+			&cluster, &num_clusters, false, &balloc);
+	if (err)
+		goto out;
+
+	cluster_offset = EXFAT_CLU_OFFSET(offset, sbi);
+	cluster_length = EXFAT_CLU_TO_B(num_clusters, sbi);
+	if (length > cluster_length - cluster_offset)
+		iomap->length = cluster_length - cluster_offset;
+	else
+		iomap->length = length;
+
+	iomap->addr = exfat_cluster_to_phys(sbi, cluster) + cluster_offset;
+	if (offset >= ei->valid_size)
+		iomap->type = IOMAP_UNWRITTEN;
+	else
+		iomap->type = IOMAP_MAPPED;
+
+	if (!(flags & IOMAP_ZERO) && iomap->type == IOMAP_MAPPED &&
+	    iomap->offset < ei->valid_size &&
+	    iomap->offset + iomap->length > ei->valid_size) {
+		iomap->length = round_up(ei->valid_size, 1 << inode->i_blkbits) -
+			iomap->offset;
+	}
+
+	iomap->flags |= IOMAP_F_MERGED;
+out:
+	mutex_unlock(&sbi->s_lock);
+	return err;
+}
+
+const struct iomap_ops exfat_read_iomap_ops = {
+	.iomap_begin = exfat_read_iomap_begin,
+};
+
+/*
+ * __exfat_write_iomap_begin - mapping logic for writes
+ *
+ * Maps the requested range and allocates clusters if needed.
+ */
+static int __exfat_write_iomap_begin(struct inode *inode, loff_t offset,
+		loff_t length, struct iomap *iomap)
+{
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	unsigned int cluster, num_clusters;
+	loff_t cluster_offset, cluster_length;
+	int err;
+	bool balloc = false;
+
+	num_clusters = max(EXFAT_B_TO_CLU_ROUND_UP(offset + length, sbi) -
+		EXFAT_B_TO_CLU_ROUND_UP(offset, sbi), 1);
+	mutex_lock(&sbi->s_lock);
+	err = exfat_map_cluster(inode, EXFAT_B_TO_CLU(offset, sbi),
+			&cluster, &num_clusters, true, &balloc);
+	if (err)
+		goto out;
+
+	iomap->bdev = inode->i_sb->s_bdev;
+	iomap->offset = offset;
+
+	cluster_offset = EXFAT_CLU_OFFSET(offset, sbi);
+	cluster_length = EXFAT_CLU_TO_B(num_clusters, sbi);
+	if (length > cluster_length - cluster_offset)
+		iomap->length = cluster_length - cluster_offset;
+	else
+		iomap->length = length;
+	iomap->addr = exfat_cluster_to_phys(sbi, cluster) + cluster_offset;
+	iomap->type = IOMAP_MAPPED;
+	if (balloc)
+		iomap->flags = IOMAP_F_NEW;
+out:
+	mutex_unlock(&sbi->s_lock);
+	return err;
+}
+
+/*
+ * exfat_write_iomap_begin - Mapping for write operations
+ *
+ * Extends ->valid_size if the write starts beyond current initialized size.
+ * Then performs actual block mapping (possibly allocating clusters).
+ */
+static int exfat_write_iomap_begin(struct inode *inode, loff_t offset,
+		loff_t length, unsigned int flags, struct iomap *iomap,
+		struct iomap *srcmap)
+{
+	int ret;
+
+	if (EXFAT_I(inode)->valid_size < offset) {
+		ret = exfat_extend_valid_size(inode, offset,
+				flags & IOMAP_DIRECT ? true : false);
+		if (ret)
+			return ret;
+	}
+
+	ret = __exfat_write_iomap_begin(inode, offset, length, iomap);
+
+	if (!(flags & IOMAP_DIRECT) && !ret &&
+	    i_size_read(inode) < iomap->offset + iomap->length) {
+		i_size_write(inode, iomap->offset + iomap->length);
+		mark_inode_dirty(inode);
+	}
+
+	return ret;
+}
+
+/*
+ * exfat_write_iomap_end - Update the state after write
+ *
+ * Extends ->valid_size to cover the newly written range.
+ * Marks the inode dirty if metadata was changed.
+ */
+static int exfat_write_iomap_end(struct inode *inode, loff_t pos, loff_t length,
+		ssize_t written, unsigned int flags, struct iomap *iomap)
+{
+	if (written) {
+		struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
+		struct exfat_inode_info *ei = EXFAT_I(inode);
+		bool dirtied = false;
+		loff_t end = pos + written;
+
+		mutex_lock(&sbi->s_lock);
+		if (ei->valid_size < end) {
+			ei->valid_size = end;
+			dirtied = true;
+		}
+		mutex_unlock(&sbi->s_lock);
+		if (dirtied)
+			mark_inode_dirty(inode);
+	}
+
+	return written;
+}
+
+const struct iomap_ops exfat_write_iomap_ops = {
+	.iomap_begin	= exfat_write_iomap_begin,
+	.iomap_end	= exfat_write_iomap_end,
+};
+
+static int exfat_mkwrite_iomap_begin(struct inode *inode, loff_t offset,
+		loff_t length, unsigned int flags, struct iomap *iomap,
+		struct iomap *srcmap)
+{
+	return __exfat_write_iomap_begin(inode, offset, length, iomap);
+}
+
+const struct iomap_ops exfat_mkwrite_iomap_ops = {
+	.iomap_begin	= exfat_mkwrite_iomap_begin,
+	.iomap_end	= exfat_write_iomap_end,
+};
+
+/*
+ * exfat_writeback_range - Map folio during writeback
+ *
+ * Called for each folio during writeback. If the folio falls outside the
+ * current iomap, remaps by calling read_iomap_begin.
+ */
+static ssize_t exfat_writeback_range(struct iomap_writepage_ctx *wpc,
+		struct folio *folio, u64 offset, unsigned int len, u64 end_pos)
+{
+	if (offset < wpc->iomap.offset ||
+	    offset >= wpc->iomap.offset + wpc->iomap.length) {
+		int error;
+
+		error = exfat_read_iomap_begin(wpc->inode, offset, len,
+				0, &wpc->iomap, NULL);
+		if (error)
+			return error;
+	}
+
+	return iomap_add_to_ioend(wpc, folio, offset, end_pos, len);
+}
+
+const struct iomap_writeback_ops exfat_writeback_ops = {
+	.writeback_range	= exfat_writeback_range,
+	.writeback_submit	= iomap_ioend_writeback_submit,
+};
diff --git a/fs/exfat/iomap.h b/fs/exfat/iomap.h
new file mode 100644
index 000000000000..4abe0dc452ee
--- /dev/null
+++ b/fs/exfat/iomap.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2026 Namjae Jeon <linkinjeon@kernel.org>
+ */
+
+#ifndef _LINUX_EXFAT_IOMAP_H
+#define _LINUX_EXFAT_IOMAP_H
+
+extern const struct iomap_write_ops exfat_iomap_folio_ops;
+extern const struct iomap_ops exfat_read_iomap_ops;
+extern const struct iomap_ops exfat_write_iomap_ops;
+extern const struct iomap_dio_ops exfat_write_dio_ops;
+extern const struct iomap_writeback_ops exfat_writeback_ops;
+extern const struct iomap_ops exfat_mkwrite_iomap_ops;
+
+#endif /* _LINUX_EXFAT_IOMAP_H */
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index 83396fd265cd..b69c4b0a926b 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -499,6 +499,7 @@ static int exfat_read_boot_sector(struct super_block *sb)
 	if (p_boot->num_fats == 2)
 		sbi->FAT2_start_sector += sbi->num_FAT_sectors;
 	sbi->data_start_sector = le32_to_cpu(p_boot->clu_offset);
+	sbi->data_start_bytes = sbi->data_start_sector << p_boot->sect_size_bits;
 	sbi->num_sectors = le64_to_cpu(p_boot->vol_length);
 	/* because the cluster index starts with 2 */
 	sbi->num_clusters = le32_to_cpu(p_boot->clu_count) +
-- 
2.25.1

[PATCH 2/5] exfat: add iomap direct I/O support

[Namjae Jeon]

Add iomap-based direct I/O support to the exfat filesystem. This replaces
the previous exfat_direct_IO() implementation that used
blockdev_direct_IO() with the modern iomap_dio_rw() interface.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/file.c  | 30 ++++++++++++++++++++++++++++--
 fs/exfat/inode.c | 45 +--------------------------------------------
 2 files changed, 29 insertions(+), 46 deletions(-)

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 756846b774c4..2a9263b4433b 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -698,7 +698,13 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 			goto unlock;
 	}
 
-	ret = __generic_file_write_iter(iocb, iter);
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		ret = iomap_dio_rw(iocb, iter, &exfat_write_iomap_ops,
+				&exfat_write_dio_ops, 0, NULL, 0);
+		if (ret == -ENOTBLK)
+			ret = 0;
+	} else
+		ret = __generic_file_write_iter(iocb, iter);
 	if (ret < 0)
 		goto unlock;
 
@@ -725,11 +731,31 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
 
 	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
 		return -EIO;
 
-	return generic_file_read_iter(iocb, iter);
+	inode_lock_shared(inode);
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		size_t count = iov_iter_count(iter);
+
+		if ((iocb->ki_pos | count) & (inode->i_sb->s_blocksize - 1)) {
+			ret = -EINVAL;
+			goto inode_unlock;
+		}
+
+		file_accessed(iocb->ki_filp);
+		ret = iomap_dio_rw(iocb, iter, &exfat_read_iomap_ops, NULL, 0,
+				NULL, 0);
+	} else {
+		ret = generic_file_read_iter(iocb, iter);
+	}
+
+inode_unlock:
+	inode_unlock_shared(inode);
+
+	return ret;
 }
 
 static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index cc54cce65a31..2985b5d736f6 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -478,49 +478,6 @@ static int exfat_write_end(const struct kiocb *iocb,
 	return err;
 }
 
-static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
-{
-	struct address_space *mapping = iocb->ki_filp->f_mapping;
-	struct inode *inode = mapping->host;
-	struct exfat_inode_info *ei = EXFAT_I(inode);
-	loff_t pos = iocb->ki_pos;
-	loff_t size = pos + iov_iter_count(iter);
-	int rw = iov_iter_rw(iter);
-	ssize_t ret;
-
-	/*
-	 * Need to use the DIO_LOCKING for avoiding the race
-	 * condition of exfat_get_block() and ->truncate().
-	 */
-	ret = blockdev_direct_IO(iocb, inode, iter, exfat_get_block);
-	if (ret < 0) {
-		if (rw == WRITE && ret != -EIOCBQUEUED)
-			exfat_write_failed(mapping, size);
-
-		return ret;
-	}
-
-	size = pos + ret;
-
-	if (rw == WRITE) {
-		/*
-		 * If the block had been partially written before this write,
-		 * ->valid_size will not be updated in exfat_get_block(),
-		 * update it here.
-		 */
-		if (ei->valid_size < size) {
-			ei->valid_size = size;
-			mark_inode_dirty(inode);
-		}
-	} else if (pos < ei->valid_size && ei->valid_size < size) {
-		/* zero the unwritten part in the partially written block */
-		iov_iter_revert(iter, size - ei->valid_size);
-		iov_iter_zero(size - ei->valid_size, iter);
-	}
-
-	return ret;
-}
-
 static sector_t exfat_aop_bmap(struct address_space *mapping, sector_t block)
 {
 	sector_t blocknr;
@@ -552,7 +509,7 @@ static const struct address_space_operations exfat_aops = {
 	.writepages	= exfat_writepages,
 	.write_begin	= exfat_write_begin,
 	.write_end	= exfat_write_end,
-	.direct_IO	= exfat_direct_IO,
+	.direct_IO	= noop_direct_IO,
 	.bmap		= exfat_aop_bmap,
 	.migrate_folio	= buffer_migrate_folio,
 };
-- 
2.25.1

[PATCH 3/5] exfat: add iomap buffered I/O support

[Namjae Jeon]

Add full buffered I/O support using the iomap framework to the exfat
filesystem. This replaces the old exfat_get_block(), exfat_write_begin(),
exfat_write_end(), and exfat_block_truncate_page() functions with their
iomap equivalents. Buffered writes now use iomap_file_buffered_write(),
read uses iomap_bio_read_folio() and iomap_bio_readahead(), and writeback
is handled through iomap_writepages().

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/exfat_fs.h |   3 +-
 fs/exfat/file.c     | 160 +++++++++++++++++++--------
 fs/exfat/inode.c    | 261 ++++----------------------------------------
 3 files changed, 142 insertions(+), 282 deletions(-)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 860f2e438b63..54da001a8f55 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -87,7 +87,7 @@ enum {
 /*
  * helpers for cluster size to byte conversion.
  */
-#define EXFAT_CLU_TO_B(b, sbi)		((b) << (sbi)->cluster_size_bits)
+#define EXFAT_CLU_TO_B(b, sbi)		((loff_t)(b) << (sbi)->cluster_size_bits)
 #define EXFAT_B_TO_CLU(b, sbi)		((b) >> (sbi)->cluster_size_bits)
 #define EXFAT_B_TO_CLU_ROUND_UP(b, sbi)	\
 	(((b - 1) >> (sbi)->cluster_size_bits) + 1)
@@ -551,7 +551,6 @@ struct inode *exfat_iget(struct super_block *sb, loff_t i_pos);
 int __exfat_write_inode(struct inode *inode, int sync);
 int exfat_write_inode(struct inode *inode, struct writeback_control *wbc);
 void exfat_evict_inode(struct inode *inode);
-int exfat_block_truncate_page(struct inode *inode, loff_t from);
 int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 		unsigned int *clu, unsigned int *count, int create,
 		bool *balloc);
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 2a9263b4433b..5f85e2e0a71e 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -337,7 +337,18 @@ int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 
 	if ((attr->ia_valid & ATTR_SIZE) &&
 	    attr->ia_size > i_size_read(inode)) {
+		loff_t old_size = i_size_read(inode);
+
 		error = exfat_cont_expand(inode, attr->ia_size);
+		if (!error && attr->ia_size > old_size &&
+		    old_size % PAGE_SIZE != 0) {
+			loff_t len = min_t(loff_t,
+					round_up(old_size, PAGE_SIZE) - old_size,
+					attr->ia_size - old_size);
+			error = iomap_zero_range(inode, old_size, len,
+					NULL, &exfat_read_iomap_ops,
+					&exfat_iomap_folio_ops, NULL);
+		}
 		if (error || attr->ia_valid == ATTR_SIZE)
 			return error;
 		attr->ia_valid &= ~ATTR_SIZE;
@@ -384,7 +395,10 @@ int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	exfat_truncate_inode_atime(inode);
 
 	if (attr->ia_valid & ATTR_SIZE) {
-		error = exfat_block_truncate_page(inode, attr->ia_size);
+		inode_dio_wait(inode);
+		error = iomap_truncate_page(inode, attr->ia_size, NULL,
+				&exfat_read_iomap_ops,
+				&exfat_iomap_folio_ops, NULL);
 		if (error)
 			goto out;
 
@@ -619,10 +633,14 @@ int exfat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
 		return -EIO;
 
-	err = __generic_file_fsync(filp, start, end, datasync);
+	err = file_write_and_wait_range(filp, start, end);
 	if (err)
 		return err;
 
+	if (!datasync)
+		err = __exfat_write_inode(inode, 1);
+	write_inode_now(inode, !datasync);
+
 	err = sync_blockdev(inode->i_sb->s_bdev);
 	if (err)
 		return err;
@@ -648,12 +666,56 @@ int exfat_extend_valid_size(struct inode *inode, loff_t off, bool bsync)
 				NULL);
 		if (!ret && bsync)
 			ret = filemap_write_and_wait_range(inode->i_mapping,
-					old_valid_size, off - 1);
+							   old_valid_size,
+							   off - 1);
 	}
 
 	return ret;
 }
 
+static ssize_t exfat_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	ssize_t ret;
+
+	ret = iomap_dio_rw(iocb, from, &exfat_write_iomap_ops,
+			&exfat_write_dio_ops, 0, NULL, 0);
+	if (ret == -ENOTBLK)
+		ret = 0;
+	else if (ret < 0)
+		goto out;
+
+	if (iov_iter_count(from)) {
+		loff_t offset, end;
+		ssize_t written;
+		int ret2;
+
+		offset = iocb->ki_pos;
+		iocb->ki_flags &= ~IOCB_DIRECT;
+		written = iomap_file_buffered_write(iocb, from,
+				&exfat_write_iomap_ops, &exfat_iomap_folio_ops,
+				NULL);
+		if (written < 0) {
+			ret = written;
+			goto out;
+		}
+
+		ret += written;
+		end = iocb->ki_pos + written - 1;
+		ret2 = filemap_write_and_wait_range(iocb->ki_filp->f_mapping,
+				offset, end);
+		if (ret2) {
+			ret = -EIO;
+			goto out;
+		}
+		if (!ret2)
+			invalidate_mapping_pages(iocb->ki_filp->f_mapping,
+					offset >> PAGE_SHIFT,
+					end >> PAGE_SHIFT);
+	}
+out:
+	return ret;
+}
+
 static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	ssize_t ret;
@@ -662,6 +724,7 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	struct exfat_inode_info *ei = EXFAT_I(inode);
 	loff_t pos = iocb->ki_pos;
 	loff_t valid_size;
+	int err;
 
 	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
 		return -EIO;
@@ -677,34 +740,18 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	if (ret <= 0)
 		goto unlock;
 
-	if (iocb->ki_flags & IOCB_DIRECT) {
-		unsigned long align = pos | iov_iter_alignment(iter);
-
-		if (!IS_ALIGNED(align, i_blocksize(inode)) &&
-		    !IS_ALIGNED(align, bdev_logical_block_size(inode->i_sb->s_bdev))) {
-			ret = -EINVAL;
-			goto unlock;
-		}
-	}
-
-	if (pos > valid_size) {
-		ret = exfat_extend_valid_size(inode, pos, false);
-		if (ret < 0 && ret != -ENOSPC) {
-			exfat_err(inode->i_sb,
-				"write: fail to zero from %llu to %llu(%zd)",
-				valid_size, pos, ret);
-		}
-		if (ret < 0)
-			goto unlock;
+	err = file_modified(iocb->ki_filp);
+	if (err) {
+		ret = err;
+		goto unlock;
 	}
 
-	if (iocb->ki_flags & IOCB_DIRECT) {
-		ret = iomap_dio_rw(iocb, iter, &exfat_write_iomap_ops,
-				&exfat_write_dio_ops, 0, NULL, 0);
-		if (ret == -ENOTBLK)
-			ret = 0;
-	} else
-		ret = __generic_file_write_iter(iocb, iter);
+	if (iocb->ki_flags & IOCB_DIRECT)
+		ret = exfat_dio_write_iter(iocb, iter);
+	else
+		ret = iomap_file_buffered_write(iocb, iter,
+				&exfat_write_iomap_ops, &exfat_iomap_folio_ops,
+				NULL);
 	if (ret < 0)
 		goto unlock;
 
@@ -737,6 +784,7 @@ static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		return -EIO;
 
 	inode_lock_shared(inode);
+
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		size_t count = iov_iter_count(iter);
 
@@ -760,28 +808,22 @@ static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 
 static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)
 {
-	int err;
 	struct inode *inode = file_inode(vmf->vma->vm_file);
-	struct exfat_inode_info *ei = EXFAT_I(inode);
-	loff_t new_valid_size;
+	vm_fault_t ret;
 
 	if (!inode_trylock(inode))
 		return VM_FAULT_RETRY;
 
-	new_valid_size = ((loff_t)vmf->pgoff + 1) << PAGE_SHIFT;
-	new_valid_size = min(new_valid_size, i_size_read(inode));
-
-	if (ei->valid_size < new_valid_size) {
-		err = exfat_extend_valid_size(inode, new_valid_size, false);
-		if (err < 0) {
-			inode_unlock(inode);
-			return vmf_fs_error(err);
-		}
-	}
+	sb_start_pagefault(inode->i_sb);
+	file_update_time(vmf->vma->vm_file);
 
+	filemap_invalidate_lock_shared(inode->i_mapping);
+	ret = iomap_page_mkwrite(vmf, &exfat_mkwrite_iomap_ops, NULL);
+	filemap_invalidate_unlock_shared(inode->i_mapping);
+	sb_end_pagefault(inode->i_sb);
 	inode_unlock(inode);
 
-	return filemap_page_mkwrite(vmf);
+	return ret;
 }
 
 static const struct vm_operations_struct exfat_file_vm_ops = {
@@ -797,6 +839,21 @@ static int exfat_file_mmap_prepare(struct vm_area_desc *desc)
 	if (unlikely(exfat_forced_shutdown(file_inode(desc->file)->i_sb)))
 		return -EIO;
 
+	if (vma_desc_test_flags(desc, VMA_WRITE_BIT)) {
+		struct inode *inode = file_inode(file);
+		loff_t from, to;
+		int err;
+
+		from = ((loff_t)desc->pgoff << PAGE_SHIFT);
+		to = min_t(loff_t, i_size_read(inode),
+				from + vma_desc_size(desc));
+		if (EXFAT_I(inode)->valid_size < to) {
+			err = exfat_extend_valid_size(inode, to, false);
+			if (err)
+				return err;
+		}
+	}
+
 	file_accessed(file);
 	desc->vm_ops = &exfat_file_vm_ops;
 	return 0;
@@ -811,7 +868,24 @@ static ssize_t exfat_splice_read(struct file *in, loff_t *ppos,
 	return filemap_splice_read(in, ppos, pipe, len, flags);
 }
 
+static int exfat_file_open(struct inode *inode, struct file *filp)
+{
+	int err;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	err = generic_file_open(inode, filp);
+	if (err)
+		return err;
+
+	filp->f_mode |= FMODE_CAN_ODIRECT;
+
+	return 0;
+}
+
 const struct file_operations exfat_file_operations = {
+	.open		= exfat_file_open,
 	.llseek		= generic_file_llseek,
 	.read_iter	= exfat_file_read_iter,
 	.write_iter	= exfat_file_write_iter,
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index 2985b5d736f6..c53ae9293cfe 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -13,9 +13,11 @@
 #include <linux/uio.h>
 #include <linux/random.h>
 #include <linux/iversion.h>
+#include <linux/iomap.h>
 
 #include "exfat_raw.h"
 #include "exfat_fs.h"
+#include "iomap.h"
 
 int __exfat_write_inode(struct inode *inode, int sync)
 {
@@ -76,15 +78,7 @@ int __exfat_write_inode(struct inode *inode, int sync)
 		on_disk_size = 0;
 
 	ep2->dentry.stream.size = cpu_to_le64(on_disk_size);
-	/*
-	 * mmap write does not use exfat_write_end(), valid_size may be
-	 * extended to the sector-aligned length in exfat_get_block().
-	 * So we need to fixup valid_size to the writren length.
-	 */
-	if (on_disk_size < ei->valid_size)
-		ep2->dentry.stream.valid_size = ep2->dentry.stream.size;
-	else
-		ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);
+	ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);
 
 	if (on_disk_size) {
 		ep2->dentry.stream.flags = ei->flags;
@@ -246,155 +240,10 @@ int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 	return 0;
 }
 
-static int exfat_get_block(struct inode *inode, sector_t iblock,
-		struct buffer_head *bh_result, int create)
-{
-	struct exfat_inode_info *ei = EXFAT_I(inode);
-	struct super_block *sb = inode->i_sb;
-	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
-	int err = 0;
-	unsigned long mapped_blocks = 0;
-	unsigned int cluster, sec_offset, count;
-	sector_t last_block;
-	sector_t phys = 0;
-	sector_t valid_blks;
-	loff_t i_size;
-	bool balloc;
-
-	mutex_lock(&sbi->s_lock);
-	i_size = i_size_read(inode);
-	last_block = EXFAT_B_TO_BLK_ROUND_UP(i_size, sb);
-	if (iblock >= last_block && !create)
-		goto done;
-
-	/* Is this block already allocated? */
-	count = EXFAT_B_TO_CLU_ROUND_UP(bh_result->b_size, sbi);
-	err = exfat_map_cluster(inode, iblock >> sbi->sect_per_clus_bits,
-			&cluster, &count, create, &balloc);
-	if (err) {
-		if (err != -ENOSPC)
-			exfat_fs_error_ratelimit(sb,
-				"failed to bmap (inode : %p iblock : %llu, err : %d)",
-				inode, (unsigned long long)iblock, err);
-		goto unlock_ret;
-	}
-
-	if (cluster == EXFAT_EOF_CLUSTER)
-		goto done;
-
-	/* sector offset in cluster */
-	sec_offset = iblock & (sbi->sect_per_clus - 1);
-
-	phys = exfat_cluster_to_sector(sbi, cluster) + sec_offset;
-	mapped_blocks = ((unsigned long)count << sbi->sect_per_clus_bits) - sec_offset;
-	max_blocks = min(mapped_blocks, max_blocks);
-
-	map_bh(bh_result, sb, phys);
-	if (buffer_delay(bh_result))
-		clear_buffer_delay(bh_result);
-
-	/*
-	 * In most cases, we just need to set bh_result to mapped, unmapped
-	 * or new status as follows:
-	 *  1. i_size == valid_size
-	 *  2. write case (create == 1)
-	 *  3. direct_read (!bh_result->b_folio)
-	 *     -> the unwritten part will be zeroed in exfat_direct_IO()
-	 *
-	 * Otherwise, in the case of buffered read, it is necessary to take
-	 * care the last nested block if valid_size is not equal to i_size.
-	 */
-	if (i_size == ei->valid_size || create || !bh_result->b_folio)
-		valid_blks = EXFAT_B_TO_BLK_ROUND_UP(ei->valid_size, sb);
-	else
-		valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);
-
-	/* The range has been fully written, map it */
-	if (iblock + max_blocks < valid_blks)
-		goto done;
-
-	/* The range has been partially written, map the written part */
-	if (iblock < valid_blks) {
-		max_blocks = valid_blks - iblock;
-		goto done;
-	}
-
-	/* The area has not been written, map and mark as new for create case */
-	if (create) {
-		set_buffer_new(bh_result);
-		ei->valid_size = EXFAT_BLK_TO_B(iblock + max_blocks, sb);
-		mark_inode_dirty(inode);
-		goto done;
-	}
-
-	/*
-	 * The area has just one block partially written.
-	 * In that case, we should read and fill the unwritten part of
-	 * a block with zero.
-	 */
-	if (bh_result->b_folio && iblock == valid_blks &&
-	    (ei->valid_size & (sb->s_blocksize - 1))) {
-		loff_t size, pos;
-		void *addr;
-
-		max_blocks = 1;
-
-		/*
-		 * No buffer_head is allocated.
-		 * (1) bmap: It's enough to set blocknr without I/O.
-		 * (2) read: The unwritten part should be filled with zero.
-		 *           If a folio does not have any buffers,
-		 *           let's returns -EAGAIN to fallback to
-		 *           block_read_full_folio() for per-bh IO.
-		 */
-		if (!folio_buffers(bh_result->b_folio)) {
-			err = -EAGAIN;
-			goto done;
-		}
-
-		pos = EXFAT_BLK_TO_B(iblock, sb);
-		size = ei->valid_size - pos;
-		addr = folio_address(bh_result->b_folio) +
-			offset_in_folio(bh_result->b_folio, pos);
-
-		/* Check if bh->b_data points to proper addr in folio */
-		if (bh_result->b_data != addr) {
-			exfat_fs_error_ratelimit(sb,
-					"b_data(%p) != folio_addr(%p)",
-					bh_result->b_data, addr);
-			err = -EINVAL;
-			goto done;
-		}
-
-		/* Read a block */
-		err = bh_read(bh_result, 0);
-		if (err < 0)
-			goto done;
-
-		/* Zero unwritten part of a block */
-		memset(bh_result->b_data + size, 0, bh_result->b_size - size);
-		err = 0;
-		goto done;
-	}
-
-	/*
-	 * The area has not been written, clear mapped for read/bmap cases.
-	 * If so, it will be filled with zero without reading from disk.
-	 */
-	clear_buffer_mapped(bh_result);
-done:
-	bh_result->b_size = EXFAT_BLK_TO_B(max_blocks, sb);
-	if (err < 0)
-		clear_buffer_mapped(bh_result);
-unlock_ret:
-	mutex_unlock(&sbi->s_lock);
-	return err;
-}
-
 static int exfat_read_folio(struct file *file, struct folio *folio)
 {
-	return mpage_read_folio(folio, exfat_get_block);
+	iomap_bio_read_folio(folio, &exfat_read_iomap_ops);
+	return 0;
 }
 
 static void exfat_readahead(struct readahead_control *rac)
@@ -410,108 +259,46 @@ static void exfat_readahead(struct readahead_control *rac)
 	    ei->valid_size < pos + readahead_length(rac))
 		return;
 
-	mpage_readahead(rac, exfat_get_block);
+	iomap_bio_readahead(rac, &exfat_read_iomap_ops);
 }
 
 static int exfat_writepages(struct address_space *mapping,
 		struct writeback_control *wbc)
 {
-	if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
-		return -EIO;
-
-	return mpage_writepages(mapping, wbc, exfat_get_block);
-}
-
-static void exfat_write_failed(struct address_space *mapping, loff_t to)
-{
-	struct inode *inode = mapping->host;
-
-	if (to > i_size_read(inode)) {
-		truncate_pagecache(inode, i_size_read(inode));
-		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
-		exfat_truncate(inode);
-	}
-}
-
-static int exfat_write_begin(const struct kiocb *iocb,
-			     struct address_space *mapping,
-			     loff_t pos, unsigned int len,
-			     struct folio **foliop, void **fsdata)
-{
-	int ret;
+	struct iomap_writepage_ctx wpc = {
+		.inode		= mapping->host,
+		.wbc		= wbc,
+		.ops		= &exfat_writeback_ops,
+	};
 
 	if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
 		return -EIO;
 
-	ret = block_write_begin(mapping, pos, len, foliop, exfat_get_block);
-
-	if (ret < 0)
-		exfat_write_failed(mapping, pos+len);
-
-	return ret;
-}
-
-static int exfat_write_end(const struct kiocb *iocb,
-			   struct address_space *mapping,
-			   loff_t pos, unsigned int len, unsigned int copied,
-			   struct folio *folio, void *fsdata)
-{
-	struct inode *inode = mapping->host;
-	struct exfat_inode_info *ei = EXFAT_I(inode);
-	int err;
-
-	err = generic_write_end(iocb, mapping, pos, len, copied, folio, fsdata);
-	if (err < len)
-		exfat_write_failed(mapping, pos+len);
-
-	if (!(err < 0) && pos + err > ei->valid_size) {
-		ei->valid_size = pos + err;
-		mark_inode_dirty(inode);
-	}
-
-	if (!(err < 0) && !(ei->attr & EXFAT_ATTR_ARCHIVE)) {
-		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
-		ei->attr |= EXFAT_ATTR_ARCHIVE;
-		mark_inode_dirty(inode);
-	}
-
-	return err;
+	return iomap_writepages(&wpc);
 }
 
 static sector_t exfat_aop_bmap(struct address_space *mapping, sector_t block)
 {
 	sector_t blocknr;
 
-	/* exfat_get_cluster() assumes the requested blocknr isn't truncated. */
 	down_read(&EXFAT_I(mapping->host)->truncate_lock);
-	blocknr = generic_block_bmap(mapping, block, exfat_get_block);
+	blocknr = iomap_bmap(mapping, block, &exfat_read_iomap_ops);
 	up_read(&EXFAT_I(mapping->host)->truncate_lock);
 	return blocknr;
 }
 
-/*
- * exfat_block_truncate_page() zeroes out a mapping from file offset `from'
- * up to the end of the block which corresponds to `from'.
- * This is required during truncate to physically zeroout the tail end
- * of that block so it doesn't yield old data if the file is later grown.
- * Also, avoid causing failure from fsx for cases of "data past EOF"
- */
-int exfat_block_truncate_page(struct inode *inode, loff_t from)
-{
-	return block_truncate_page(inode->i_mapping, from, exfat_get_block);
-}
-
 static const struct address_space_operations exfat_aops = {
-	.dirty_folio	= block_dirty_folio,
-	.invalidate_folio = block_invalidate_folio,
-	.read_folio	= exfat_read_folio,
-	.readahead	= exfat_readahead,
-	.writepages	= exfat_writepages,
-	.write_begin	= exfat_write_begin,
-	.write_end	= exfat_write_end,
-	.direct_IO	= noop_direct_IO,
-	.bmap		= exfat_aop_bmap,
-	.migrate_folio	= buffer_migrate_folio,
+	.read_folio		= exfat_read_folio,
+	.readahead		= exfat_readahead,
+	.writepages		= exfat_writepages,
+	.direct_IO		= noop_direct_IO,
+	.dirty_folio		= iomap_dirty_folio,
+	.bmap			= exfat_aop_bmap,
+	.migrate_folio		= filemap_migrate_folio,
+	.is_partially_uptodate	= iomap_is_partially_uptodate,
+	.error_remove_folio	= generic_error_remove_folio,
+	.release_folio		= iomap_release_folio,
+	.invalidate_folio	= iomap_invalidate_folio,
 };
 
 static inline unsigned long exfat_hash(loff_t i_pos)
-- 
2.25.1

[PATCH 4/5] exfat: add support for multi-cluster allocation

[Namjae Jeon]

Currently exfat_map_cluster() allocates and returns only one cluster
at a time even when more clusters are needed. This causes multiple
FAT walks and repeated allocation calls during large sequential writes
or when using iomap for writes. This change exfat_map_cluster() and
exfat_alloc_cluster() to be able to allocate multiple contiguous
clusters.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/dir.c      |  2 +-
 fs/exfat/exfat_fs.h |  2 +-
 fs/exfat/fatent.c   | 26 ++++++++++++++++----------
 fs/exfat/file.c     |  2 +-
 fs/exfat/inode.c    | 32 +++++---------------------------
 fs/exfat/namei.c    |  2 +-
 6 files changed, 25 insertions(+), 41 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index a2c2b998808c..857b22e431cd 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -308,7 +308,7 @@ int exfat_alloc_new_dir(struct inode *inode, struct exfat_chain *clu)
 
 	exfat_chain_set(clu, EXFAT_EOF_CLUSTER, 0, ALLOC_NO_FAT_CHAIN);
 
-	ret = exfat_alloc_cluster(inode, 1, clu, IS_DIRSYNC(inode));
+	ret = exfat_alloc_cluster(inode, 1, clu, IS_DIRSYNC(inode), false);
 	if (ret)
 		return ret;
 
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 54da001a8f55..5992755b5ab3 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -448,7 +448,7 @@ int exfat_clear_volume_dirty(struct super_block *sb);
 #define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu, NULL)
 
 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
-		struct exfat_chain *p_chain, bool sync_bmap);
+		struct exfat_chain *p_chain, bool sync_bmap, bool contig);
 int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain);
 int exfat_ent_get(struct super_block *sb, unsigned int loc,
 		unsigned int *content, struct buffer_head **last);
diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index f2e5d5dde393..758c2d971e73 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -424,7 +424,7 @@ int exfat_zeroed_cluster(struct inode *dir, unsigned int clu)
 }
 
 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
-		struct exfat_chain *p_chain, bool sync_bmap)
+		struct exfat_chain *p_chain, bool sync_bmap, bool contig)
 {
 	int ret = -ENOSPC;
 	unsigned int total_cnt;
@@ -475,14 +475,20 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 
 	while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) !=
 	       EXFAT_EOF_CLUSTER) {
-		if (new_clu != hint_clu &&
-		    p_chain->flags == ALLOC_NO_FAT_CHAIN) {
-			if (exfat_chain_cont_cluster(sb, p_chain->dir,
-					p_chain->size)) {
-				ret = -EIO;
-				goto free_cluster;
+		if (new_clu != hint_clu) {
+			if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
+				if (exfat_chain_cont_cluster(sb, p_chain->dir,
+							     p_chain->size)) {
+					ret = -EIO;
+					goto free_cluster;
+				}
+				p_chain->flags = ALLOC_FAT_CHAIN;
+			}
+
+			if (contig && p_chain->size > 0) {
+				hint_clu--;
+				goto done;
 			}
-			p_chain->flags = ALLOC_FAT_CHAIN;
 		}
 
 		/* update allocation bitmap */
@@ -512,9 +518,9 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 		last_clu = new_clu;
 
 		if (p_chain->size == num_alloc) {
+done:
 			sbi->clu_srch_ptr = hint_clu;
-			sbi->used_clusters += num_alloc;
-
+			sbi->used_clusters += p_chain->size;
 			mutex_unlock(&sbi->bitmap_lock);
 			return 0;
 		}
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 5f85e2e0a71e..d7857aec072b 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -57,7 +57,7 @@ static int exfat_cont_expand(struct inode *inode, loff_t size)
 	clu.flags = ei->flags;
 
 	ret = exfat_alloc_cluster(inode, new_num_clusters - num_clusters,
-			&clu, inode_needs_sync(inode));
+			&clu, inode_needs_sync(inode), false);
 	if (ret)
 		return ret;
 
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index c53ae9293cfe..46dc98ef1afb 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -128,14 +128,10 @@ int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct exfat_inode_info *ei = EXFAT_I(inode);
 	unsigned int local_clu_offset = clu_offset;
-	unsigned int num_to_be_allocated = 0, num_clusters;
+	unsigned int num_to_be_allocated = *count, num_clusters;
 
 	num_clusters = EXFAT_B_TO_CLU(exfat_ondisk_size(inode), sbi);
-
-	if (clu_offset >= num_clusters)
-		num_to_be_allocated = clu_offset - num_clusters + 1;
-
-	if (!create && (num_to_be_allocated > 0)) {
+	if (!create && clu_offset >= num_clusters) {
 		*clu = EXFAT_EOF_CLUSTER;
 		return 0;
 	}
@@ -176,7 +172,7 @@ int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 		}
 
 		ret = exfat_alloc_cluster(inode, num_to_be_allocated, &new_clu,
-				inode_needs_sync(inode));
+				inode_needs_sync(inode), true);
 		if (ret)
 			return ret;
 
@@ -210,26 +206,8 @@ int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 		}
 
 		*clu = new_clu.dir;
-
-		inode->i_blocks += EXFAT_CLU_TO_B(num_to_be_allocated, sbi) >> 9;
-
-		/*
-		 * Move *clu pointer along FAT chains (hole care) because the
-		 * caller of this function expect *clu to be the last cluster.
-		 * This only works when num_to_be_allocated >= 2,
-		 * *clu = (the first cluster of the allocated chain) =>
-		 * (the last cluster of ...)
-		 */
-		if (ei->flags == ALLOC_NO_FAT_CHAIN) {
-			*clu += num_to_be_allocated - 1;
-		} else {
-			while (num_to_be_allocated > 1) {
-				if (exfat_get_next_cluster(sb, clu))
-					return -EIO;
-				num_to_be_allocated--;
-			}
-		}
-		*count = 1;
+		*count = new_clu.size;
+		inode->i_blocks += EXFAT_CLU_TO_B(new_clu.size, sbi) >> 9;
 		*balloc = true;
 	}
 
diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index d0ea1ff81c09..6261cd994d1d 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -347,7 +347,7 @@ int exfat_find_empty_entry(struct inode *inode,
 		}
 
 		/* allocate a cluster */
-		ret = exfat_alloc_cluster(inode, 1, &clu, IS_DIRSYNC(inode));
+		ret = exfat_alloc_cluster(inode, 1, &clu, IS_DIRSYNC(inode), false);
 		if (ret)
 			return ret;
 
-- 
2.25.1

[PATCH 5/5] exfat: add support for SEEK_HOLE and SEEK_DATA in llseek

[Namjae Jeon]

Adds exfat_file_llseek() that implements these whence values via
the iomap layer (iomap_seek_hole() and iomap_seek_data()) using the
existing exfat_read_iomap_ops.
Unlike many other modern filesystems, exFAT does not support sparse files
with unallocated clusters (holes). In exFAT, clusters are always fully
allocated once they are written or preallocated. In addition, exFAT
maintains a separate "Valid Data Length" (valid_size) that is distinct
from the logical file size. This affects how holes are reported during
seeking. In exfat_read_iomap_begin(), ranges where the offset is greater
than or equal to ei->valid_size are mapped as IOMAP_UNWRITTEN, while ranges
below valid_size are mapped as IOMAP_MAPPED. This mapping behavior is used
by the iomap seek functions to correctly report SEEK_HOLE and SEEK_DATA
positions.

  - Ranges with offset >= ei->valid_size are mapped as IOMAP_UNWRITTEN.
  - Ranges with offset < ei->valid_size are mapped as IOMAP_MAPPED.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/file.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index d7857aec072b..9a30c32b3a05 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -884,9 +884,34 @@ static int exfat_file_open(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+static loff_t exfat_file_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file->f_mapping->host;
+
+	switch (whence) {
+	case SEEK_HOLE:
+		inode_lock_shared(inode);
+		offset = iomap_seek_hole(inode, offset, &exfat_read_iomap_ops);
+		inode_unlock_shared(inode);
+		break;
+	case SEEK_DATA:
+		inode_lock_shared(inode);
+		offset = iomap_seek_data(inode, offset, &exfat_read_iomap_ops);
+		inode_unlock_shared(inode);
+		break;
+	default:
+		return generic_file_llseek_size(file, offset, whence,
+						inode->i_sb->s_maxbytes,
+						i_size_read(inode));
+	}
+	if (offset < 0)
+		return offset;
+	return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
+}
+
 const struct file_operations exfat_file_operations = {
 	.open		= exfat_file_open,
-	.llseek		= generic_file_llseek,
+	.llseek		= exfat_file_llseek,
 	.read_iter	= exfat_file_read_iter,
 	.write_iter	= exfat_file_write_iter,
 	.unlocked_ioctl = exfat_ioctl,
-- 
2.25.1