linux-kernel - [PATCH 7/9] ext4: introduce ext4_check_map_extents

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Message-ID: <20250423085257.122685-8-yi.zhang@huaweicloud.com>
Date: Wed, 23 Apr 2025 16:52:55 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	libaokun1@...wei.com,
	yukuai3@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH 7/9] ext4: introduce ext4_check_map_extents_env() debug helper

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

Loading and modifying the extents tree and extent status tree without
holding the inode's i_rwsem or the mapping's invalidate_lock is not
permitted, except during the I/O writeback. Add a new debug helper
ext4_check_map_extents_env(), it will verify whether the extent
loading/modifying context is safe.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/ext4.h  |  1 +
 fs/ext4/inode.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ccc1de1e23a9..3b1bf52737e3 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2977,6 +2977,7 @@ static inline bool ext4_mb_cr_expensive(enum criteria cr)
 void ext4_inode_csum_set(struct inode *inode, struct ext4_inode *raw,
 			 struct ext4_inode_info *ei);
 int ext4_inode_is_fast_symlink(struct inode *inode);
+void ext4_check_map_extents_env(struct inode *inode);
 struct buffer_head *ext4_getblk(handle_t *, struct inode *, ext4_lblk_t, int);
 struct buffer_head *ext4_bread(handle_t *, struct inode *, ext4_lblk_t, int);
 int ext4_bread_batch(struct inode *inode, ext4_lblk_t block, int bh_count,
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 51801f6d23ef..74c7a902a41d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -416,6 +416,32 @@ int ext4_issue_zeroout(struct inode *inode, ext4_lblk_t lblk, ext4_fsblk_t pblk,
 	return ret;
 }
 
+/*
+ * For generic regular files, when updating the extent tree, Ext4 should
+ * hold the i_rwsem and invalidate_lock exclusively. This ensures
+ * exclusion against concurrent page faults, as well as reads and writes.
+ */
+#ifdef CONFIG_EXT4_DEBUG
+void ext4_check_map_extents_env(struct inode *inode)
+{
+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return;
+
+	if (!S_ISREG(inode->i_mode) ||
+	    IS_NOQUOTA(inode) || IS_VERITY(inode) ||
+	    is_special_ino(inode->i_sb, inode->i_ino) ||
+	    (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) ||
+	    ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE) ||
+	    ext4_verity_in_progress(inode))
+		return;
+
+	WARN_ON_ONCE(!inode_is_locked(inode) &&
+		     !rwsem_is_locked(&inode->i_mapping->invalidate_lock));
+}
+#else
+void ext4_check_map_extents_env(struct inode *inode) {}
+#endif
+
 #define check_block_validity(inode, map)	\
 	__check_block_validity((inode), __func__, __LINE__, (map))
 
-- 
2.46.1