1 files changed, 219 insertions, 1 deletions

diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
index 18894ebba6db..b49fa75eab26 100644
--- a/fs/iomap/ioend.c
+++ b/fs/iomap/ioend.c
@@ -1,10 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2024-2025 Christoph Hellwig.
+ * Copyright (c) 2016-2025 Christoph Hellwig.
  */
 #include <linux/iomap.h>
 #include <linux/list_sort.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
 #include "internal.h"
+#include "trace.h"
 
 struct bio_set iomap_ioend_bioset;
 EXPORT_SYMBOL_GPL(iomap_ioend_bioset);
@@ -28,6 +31,221 @@ struct iomap_ioend *iomap_init_ioend(struct inode *inode,
 }
 EXPORT_SYMBOL_GPL(iomap_init_ioend);
 
+/*
+ * We're now finished for good with this ioend structure.  Update the folio
+ * state, release holds on bios, and finally free up memory.  Do not use the
+ * ioend after this.
+ */
+static u32 iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
+{
+	struct inode *inode = ioend->io_inode;
+	struct bio *bio = &ioend->io_bio;
+	struct folio_iter fi;
+	u32 folio_count = 0;
+
+	if (ioend->io_error) {
+		mapping_set_error(inode->i_mapping, ioend->io_error);
+		if (!bio_flagged(bio, BIO_QUIET)) {
+			pr_err_ratelimited(
+"%s: writeback error on inode %lu, offset %lld, sector %llu",
+				inode->i_sb->s_id, inode->i_ino,
+				ioend->io_offset, ioend->io_sector);
+		}
+	}
+
+	/* walk all folios in bio, ending page IO on them */
+	bio_for_each_folio_all(fi, bio) {
+		iomap_finish_folio_write(inode, fi.folio, fi.length);
+		folio_count++;
+	}
+
+	bio_put(bio);	/* frees the ioend */
+	return folio_count;
+}
+
+static void ioend_writeback_end_bio(struct bio *bio)
+{
+	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
+
+	ioend->io_error = blk_status_to_errno(bio->bi_status);
+	iomap_finish_ioend_buffered(ioend);
+}
+
+/*
+ * We cannot cancel the ioend directly in case of an error, so call the bio end
+ * I/O handler with the error status here to run the normal I/O completion
+ * handler.
+ */
+int iomap_ioend_writeback_submit(struct iomap_writepage_ctx *wpc, int error)
+{
+	struct iomap_ioend *ioend = wpc->wb_ctx;
+
+	if (!ioend->io_bio.bi_end_io)
+		ioend->io_bio.bi_end_io = ioend_writeback_end_bio;
+
+	if (WARN_ON_ONCE(wpc->iomap.flags & IOMAP_F_ANON_WRITE))
+		error = -EIO;
+
+	if (error) {
+		ioend->io_bio.bi_status = errno_to_blk_status(error);
+		bio_endio(&ioend->io_bio);
+		return error;
+	}
+
+	submit_bio(&ioend->io_bio);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iomap_ioend_writeback_submit);
+
+static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
+		loff_t pos, u16 ioend_flags)
+{
+	struct bio *bio;
+
+	bio = bio_alloc_bioset(wpc->iomap.bdev, BIO_MAX_VECS,
+			       REQ_OP_WRITE | wbc_to_write_flags(wpc->wbc),
+			       GFP_NOFS, &iomap_ioend_bioset);
+	bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos);
+	bio->bi_write_hint = wpc->inode->i_write_hint;
+	wbc_init_bio(wpc->wbc, bio);
+	wpc->nr_folios = 0;
+	return iomap_init_ioend(wpc->inode, bio, pos, ioend_flags);
+}
+
+static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
+		u16 ioend_flags)
+{
+	struct iomap_ioend *ioend = wpc->wb_ctx;
+
+	if (ioend_flags & IOMAP_IOEND_BOUNDARY)
+		return false;
+	if ((ioend_flags & IOMAP_IOEND_NOMERGE_FLAGS) !=
+	    (ioend->io_flags & IOMAP_IOEND_NOMERGE_FLAGS))
+		return false;
+	if (pos != ioend->io_offset + ioend->io_size)
+		return false;
+	if (!(wpc->iomap.flags & IOMAP_F_ANON_WRITE) &&
+	    iomap_sector(&wpc->iomap, pos) != bio_end_sector(&ioend->io_bio))
+		return false;
+	/*
+	 * Limit ioend bio chain lengths to minimise IO completion latency. This
+	 * also prevents long tight loops ending page writeback on all the
+	 * folios in the ioend.
+	 */
+	if (wpc->nr_folios >= IOEND_BATCH_SIZE)
+		return false;
+	return true;
+}
+
+/*
+ * Test to see if we have an existing ioend structure that we could append to
+ * first; otherwise finish off the current ioend and start another.
+ *
+ * If a new ioend is created and cached, the old ioend is submitted to the block
+ * layer instantly.  Batching optimisations are provided by higher level block
+ * plugging.
+ *
+ * At the end of a writeback pass, there will be a cached ioend remaining on the
+ * writepage context that the caller will need to submit.
+ */
+ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, struct folio *folio,
+		loff_t pos, loff_t end_pos, unsigned int dirty_len)
+{
+	struct iomap_ioend *ioend = wpc->wb_ctx;
+	size_t poff = offset_in_folio(folio, pos);
+	unsigned int ioend_flags = 0;
+	unsigned int map_len = min_t(u64, dirty_len,
+		wpc->iomap.offset + wpc->iomap.length - pos);
+	int error;
+
+	trace_iomap_add_to_ioend(wpc->inode, pos, dirty_len, &wpc->iomap);
+
+	WARN_ON_ONCE(!folio->private && map_len < dirty_len);
+
+	switch (wpc->iomap.type) {
+	case IOMAP_INLINE:
+		WARN_ON_ONCE(1);
+		return -EIO;
+	case IOMAP_HOLE:
+		return map_len;
+	default:
+		break;
+	}
+
+	if (wpc->iomap.type == IOMAP_UNWRITTEN)
+		ioend_flags |= IOMAP_IOEND_UNWRITTEN;
+	if (wpc->iomap.flags & IOMAP_F_SHARED)
+		ioend_flags |= IOMAP_IOEND_SHARED;
+	if (folio_test_dropbehind(folio))
+		ioend_flags |= IOMAP_IOEND_DONTCACHE;
+	if (pos == wpc->iomap.offset && (wpc->iomap.flags & IOMAP_F_BOUNDARY))
+		ioend_flags |= IOMAP_IOEND_BOUNDARY;
+
+	if (!ioend || !iomap_can_add_to_ioend(wpc, pos, ioend_flags)) {
+new_ioend:
+		if (ioend) {
+			error = wpc->ops->writeback_submit(wpc, 0);
+			if (error)
+				return error;
+		}
+		wpc->wb_ctx = ioend = iomap_alloc_ioend(wpc, pos, ioend_flags);
+	}
+
+	if (!bio_add_folio(&ioend->io_bio, folio, map_len, poff))
+		goto new_ioend;
+
+	iomap_start_folio_write(wpc->inode, folio, map_len);
+
+	/*
+	 * Clamp io_offset and io_size to the incore EOF so that ondisk
+	 * file size updates in the ioend completion are byte-accurate.
+	 * This avoids recovering files with zeroed tail regions when
+	 * writeback races with appending writes:
+	 *
+	 *    Thread 1:                  Thread 2:
+	 *    ------------               -----------
+	 *    write [A, A+B]
+	 *    update inode size to A+B
+	 *    submit I/O [A, A+BS]
+	 *                               write [A+B, A+B+C]
+	 *                               update inode size to A+B+C
+	 *    <I/O completes, updates disk size to min(A+B+C, A+BS)>
+	 *    <power failure>
+	 *
+	 *  After reboot:
+	 *    1) with A+B+C < A+BS, the file has zero padding in range
+	 *       [A+B, A+B+C]
+	 *
+	 *    |<     Block Size (BS)   >|
+	 *    |DDDDDDDDDDDD0000000000000|
+	 *    ^           ^        ^
+	 *    A          A+B     A+B+C
+	 *                       (EOF)
+	 *
+	 *    2) with A+B+C > A+BS, the file has zero padding in range
+	 *       [A+B, A+BS]
+	 *
+	 *    |<     Block Size (BS)   >|<     Block Size (BS)    >|
+	 *    |DDDDDDDDDDDD0000000000000|00000000000000000000000000|
+	 *    ^           ^             ^           ^
+	 *    A          A+B           A+BS       A+B+C
+	 *                             (EOF)
+	 *
+	 *    D = Valid Data
+	 *    0 = Zero Padding
+	 *
+	 * Note that this defeats the ability to chain the ioends of
+	 * appending writes.
+	 */
+	ioend->io_size += map_len;
+	if (ioend->io_offset + ioend->io_size > end_pos)
+		ioend->io_size = end_pos - ioend->io_offset;
+
+	wbc_account_cgroup_owner(wpc->wbc, folio, map_len);
+	return map_len;
+}
+EXPORT_SYMBOL_GPL(iomap_add_to_ioend);
+
 static u32 iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 {
 	if (ioend->io_parent) {