[PATCH 3/4] fs: add check functions for sb_start_{write,pagefault,intwrite}

[Naohiro Aota <naohiro.aota@xxxxxxx>]

Add a function sb_write_started() to return if sb_start_write() is
properly called. It is used in the next commit.

Also, add the similar functions for sb_start_pagefault() and
sb_start_intwrite().

Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
---
 include/linux/fs.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 27746a3da8fd..0c8714d64169 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1732,6 +1732,11 @@ static inline bool __sb_start_write_trylock(struct super_block *sb, int level)
 #define __sb_writers_release(sb, lev)	\
 	percpu_rwsem_release(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_)
 
+static inline bool __sb_write_started(struct super_block *sb, int level)
+{
+	return lockdep_is_held_type(sb->s_writers.rw_sem + level - 1, 1);
+}
+
 /**
  * sb_end_write - drop write access to a superblock
  * @sb: the super we wrote to
@@ -1797,6 +1802,11 @@ static inline bool sb_start_write_trylock(struct super_block *sb)
 	return __sb_start_write_trylock(sb, SB_FREEZE_WRITE);
 }
 
+static inline bool sb_write_started(struct super_block *sb)
+{
+	return __sb_write_started(sb, SB_FREEZE_WRITE);
+}
+
 /**
  * sb_start_pagefault - get write access to a superblock from a page fault
  * @sb: the super we write to
@@ -1821,6 +1831,11 @@ static inline void sb_start_pagefault(struct super_block *sb)
 	__sb_start_write(sb, SB_FREEZE_PAGEFAULT);
 }
 
+static inline bool sb_pagefault_started(struct super_block *sb)
+{
+	return __sb_write_started(sb, SB_FREEZE_PAGEFAULT);
+}
+
 /**
  * sb_start_intwrite - get write access to a superblock for internal fs purposes
  * @sb: the super we write to
@@ -1844,6 +1859,11 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb)
 	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
 }
 
+static inline bool sb_intwrite_started(struct super_block *sb)
+{
+	return __sb_write_started(sb, SB_FREEZE_FS);
+}
+
 bool inode_owner_or_capable(struct user_namespace *mnt_userns,
 			    const struct inode *inode);
 
-- 
2.35.1