linux-ext4 - [PATCH v3 5/6] ext4: make ext4_map_blocks() distinguish delalloc only extent

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Message-Id: <20240105033018.1665752-6-yi.zhang@huaweicloud.com>
Date: Fri,  5 Jan 2024 11:30:17 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com
Subject: [PATCH v3 5/6] ext4: make ext4_map_blocks() distinguish delalloc only extent

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

Add a new map flag EXT4_MAP_DELAYED to indicate the mapping range is a
delayed allocated only (not unwritten) one, and making
ext4_map_blocks() can distinguish it, no longer mixing it with holes.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/ext4.h    | 4 +++-
 fs/ext4/extents.c | 7 +++++--
 fs/ext4/inode.c   | 2 ++
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a5d784872303..55195909d32f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -252,8 +252,10 @@ struct ext4_allocation_request {
 #define EXT4_MAP_MAPPED		BIT(BH_Mapped)
 #define EXT4_MAP_UNWRITTEN	BIT(BH_Unwritten)
 #define EXT4_MAP_BOUNDARY	BIT(BH_Boundary)
+#define EXT4_MAP_DELAYED	BIT(BH_Delay)
 #define EXT4_MAP_FLAGS		(EXT4_MAP_NEW | EXT4_MAP_MAPPED |\
-				 EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY)
+				 EXT4_MAP_UNWRITTEN | EXT4_MAP_BOUNDARY |\
+				 EXT4_MAP_DELAYED)
 
 struct ext4_map_blocks {
 	ext4_fsblk_t m_pblk;
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e0b7e48c4c67..6b64319a7df8 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4076,8 +4076,11 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 		/*
 		 * The delalloc extent containing lblk, it must have been
 		 * added after ext4_map_blocks() checked the extent status
-		 * tree, adjust the length to the delalloc extent's after
-		 * lblk.
+		 * tree so we are not holding i_rwsem and delalloc info is
+		 * only stabilized by i_data_sem we are going to release
+		 * soon. Don't modify the extent status tree and report
+		 * extent as a hole, just adjust the length to the delalloc
+		 * extent's after lblk.
 		 */
 		len = es.es_lblk + es.es_len - lblk;
 		return len;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1b5e6409f958..c141bf6d8db2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -515,6 +515,8 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 			map->m_len = retval;
 		} else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) {
 			map->m_pblk = 0;
+			map->m_flags |= ext4_es_is_delayed(&es) ?
+					EXT4_MAP_DELAYED : 0;
 			retval = es.es_len - (map->m_lblk - es.es_lblk);
 			if (retval > map->m_len)
 				retval = map->m_len;
-- 
2.39.2