linux-kernel - [PATCH v3 6/9] iomap: don't increase i

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Message-Id: <20240319011102.2929635-7-yi.zhang@huaweicloud.com>
Date: Tue, 19 Mar 2024 09:10:59 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	djwong@...nel.org,
	hch@...radead.org,
	brauner@...nel.org,
	david@...morbit.com,
	tytso@....edu,
	jack@...e.cz,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com
Subject: [PATCH v3 6/9] iomap: don't increase i_size if it's not a write operation

From: Zhang Yi <yi.zhang@...wei.com>

Increase i_size in iomap_zero_range() and iomap_unshare_iter() is not
needed, the caller should handle it. Especially, when truncate partial
block, we should not increase i_size beyond the new EOF here. It doesn't
affect xfs and gfs2 now because they set the new file size after zero
out, it doesn't matter that a transient increase in i_size, but it will
affect ext4 because it set file size before truncate. So move the i_size
updating logic to iomap_write_iter().

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 fs/iomap/buffered-io.c | 50 +++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 7e32a204650b..e9112dc78d15 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -837,32 +837,13 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
-	loff_t old_size = iter->inode->i_size;
-	size_t ret;
-
-	if (srcmap->type == IOMAP_INLINE) {
-		ret = iomap_write_end_inline(iter, folio, pos, copied);
-	} else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
-		ret = block_write_end(NULL, iter->inode->i_mapping, pos, len,
-				copied, &folio->page, NULL);
-	} else {
-		ret = __iomap_write_end(iter->inode, pos, len, copied, folio);
-	}
-
-	/*
-	 * Update the in-memory inode size after copying the data into the page
-	 * cache.  It's up to the file system to write the updated size to disk,
-	 * preferably after I/O completion so that no stale data is exposed.
-	 */
-	if (pos + ret > old_size) {
-		i_size_write(iter->inode, pos + ret);
-		iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
-	}
-	__iomap_put_folio(iter, pos, ret, folio);
 
-	if (old_size < pos)
-		pagecache_isize_extended(iter->inode, old_size, pos);
-	return ret;
+	if (srcmap->type == IOMAP_INLINE)
+		return iomap_write_end_inline(iter, folio, pos, copied);
+	if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
+		return block_write_end(NULL, iter->inode->i_mapping, pos, len,
+				       copied, &folio->page, NULL);
+	return __iomap_write_end(iter->inode, pos, len, copied, folio);
 }
 
 static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
@@ -877,6 +858,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 
 	do {
 		struct folio *folio;
+		loff_t old_size;
 		size_t offset;		/* Offset into folio */
 		size_t bytes;		/* Bytes to write to folio */
 		size_t copied;		/* Bytes copied from user */
@@ -926,6 +908,22 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
 		status = iomap_write_end(iter, pos, bytes, copied, folio);
 
+		/*
+		 * Update the in-memory inode size after copying the data into
+		 * the page cache.  It's up to the file system to write the
+		 * updated size to disk, preferably after I/O completion so that
+		 * no stale data is exposed.  Only once that's done can we
+		 * unlock and release the folio.
+		 */
+		old_size = iter->inode->i_size;
+		if (pos + status > old_size) {
+			i_size_write(iter->inode, pos + status);
+			iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
+		}
+		__iomap_put_folio(iter, pos, status, folio);
+
+		if (old_size < pos)
+			pagecache_isize_extended(iter->inode, old_size, pos);
 		if (status < bytes)
 			iomap_write_failed(iter->inode, pos + status,
 					   bytes - status);
@@ -1298,6 +1296,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 			bytes = folio_size(folio) - offset;
 
 		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(bytes == 0))
 			return -EIO;
 
@@ -1362,6 +1361,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_mark_accessed(folio);
 
 		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		__iomap_put_folio(iter, pos, bytes, folio);
 		if (WARN_ON_ONCE(bytes == 0))
 			return -EIO;
 
-- 
2.39.2