1 files changed, 238 insertions, 0 deletions
diff --git a/include/linux/fs/super.h b/include/linux/fs/super.h
new file mode 100644
index 000000000000..f21ffbb6dea5
--- /dev/null
+++ b/include/linux/fs/super.h
@@ -0,0 +1,238 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_FS_SUPER_H
+#define _LINUX_FS_SUPER_H
+
+#include <linux/fs/super_types.h>
+#include <linux/unicode.h>
+
+/*
+ * These are internal functions, please use sb_start_{write,pagefault,intwrite}
+ * instead.
+ */
+static inline void __sb_end_write(struct super_block *sb, int level)
+{
+	percpu_up_read(sb->s_writers.rw_sem + level - 1);
+}
+
+static inline void __sb_start_write(struct super_block *sb, int level)
+{
+	percpu_down_read_freezable(sb->s_writers.rw_sem + level - 1, true);
+}
+
+static inline bool __sb_start_write_trylock(struct super_block *sb, int level)
+{
+	return percpu_down_read_trylock(sb->s_writers.rw_sem + level - 1);
+}
+
+#define __sb_writers_acquired(sb, lev) \
+	percpu_rwsem_acquire(&(sb)->s_writers.rw_sem[(lev) - 1], 1, _THIS_IP_)
+#define __sb_writers_release(sb, lev) \
+	percpu_rwsem_release(&(sb)->s_writers.rw_sem[(lev) - 1], _THIS_IP_)
+
+/**
+ * __sb_write_started - check if sb freeze level is held
+ * @sb: the super we write to
+ * @level: the freeze level
+ *
+ * * > 0 - sb freeze level is held
+ * *   0 - sb freeze level is not held
+ * * < 0 - !CONFIG_LOCKDEP/LOCK_STATE_UNKNOWN
+ */
+static inline int __sb_write_started(const struct super_block *sb, int level)
+{
+	return lockdep_is_held_type(sb->s_writers.rw_sem + level - 1, 1);
+}
+
+/**
+ * sb_write_started - check if SB_FREEZE_WRITE is held
+ * @sb: the super we write to
+ *
+ * May be false positive with !CONFIG_LOCKDEP/LOCK_STATE_UNKNOWN.
+ */
+static inline bool sb_write_started(const struct super_block *sb)
+{
+	return __sb_write_started(sb, SB_FREEZE_WRITE);
+}
+
+/**
+ * sb_write_not_started - check if SB_FREEZE_WRITE is not held
+ * @sb: the super we write to
+ *
+ * May be false positive with !CONFIG_LOCKDEP/LOCK_STATE_UNKNOWN.
+ */
+static inline bool sb_write_not_started(const struct super_block *sb)
+{
+	return __sb_write_started(sb, SB_FREEZE_WRITE) <= 0;
+}
+
+/**
+ * sb_end_write - drop write access to a superblock
+ * @sb: the super we wrote to
+ *
+ * Decrement number of writers to the filesystem. Wake up possible waiters
+ * wanting to freeze the filesystem.
+ */
+static inline void sb_end_write(struct super_block *sb)
+{
+	__sb_end_write(sb, SB_FREEZE_WRITE);
+}
+
+/**
+ * sb_end_pagefault - drop write access to a superblock from a page fault
+ * @sb: the super we wrote to
+ *
+ * Decrement number of processes handling write page fault to the filesystem.
+ * Wake up possible waiters wanting to freeze the filesystem.
+ */
+static inline void sb_end_pagefault(struct super_block *sb)
+{
+	__sb_end_write(sb, SB_FREEZE_PAGEFAULT);
+}
+
+/**
+ * sb_end_intwrite - drop write access to a superblock for internal fs purposes
+ * @sb: the super we wrote to
+ *
+ * Decrement fs-internal number of writers to the filesystem.  Wake up possible
+ * waiters wanting to freeze the filesystem.
+ */
+static inline void sb_end_intwrite(struct super_block *sb)
+{
+	__sb_end_write(sb, SB_FREEZE_FS);
+}
+
+/**
+ * sb_start_write - get write access to a superblock
+ * @sb: the super we write to
+ *
+ * When a process wants to write data or metadata to a file system (i.e. dirty
+ * a page or an inode), it should embed the operation in a sb_start_write() -
+ * sb_end_write() pair to get exclusion against file system freezing. This
+ * function increments number of writers preventing freezing. If the file
+ * system is already frozen, the function waits until the file system is
+ * thawed.
+ *
+ * Since freeze protection behaves as a lock, users have to preserve
+ * ordering of freeze protection and other filesystem locks. Generally,
+ * freeze protection should be the outermost lock. In particular, we have:
+ *
+ * sb_start_write
+ *   -> i_rwsem			(write path, truncate, directory ops, ...)
+ *   -> s_umount		(freeze_super, thaw_super)
+ */
+static inline void sb_start_write(struct super_block *sb)
+{
+	__sb_start_write(sb, SB_FREEZE_WRITE);
+}
+
+DEFINE_GUARD(super_write,
+	     struct super_block *,
+	     sb_start_write(_T),
+	     sb_end_write(_T))
+
+static inline bool sb_start_write_trylock(struct super_block *sb)
+{
+	return __sb_start_write_trylock(sb, SB_FREEZE_WRITE);
+}
+
+/**
+ * sb_start_pagefault - get write access to a superblock from a page fault
+ * @sb: the super we write to
+ *
+ * When a process starts handling write page fault, it should embed the
+ * operation into sb_start_pagefault() - sb_end_pagefault() pair to get
+ * exclusion against file system freezing. This is needed since the page fault
+ * is going to dirty a page. This function increments number of running page
+ * faults preventing freezing. If the file system is already frozen, the
+ * function waits until the file system is thawed.
+ *
+ * Since page fault freeze protection behaves as a lock, users have to preserve
+ * ordering of freeze protection and other filesystem locks. It is advised to
+ * put sb_start_pagefault() close to mmap_lock in lock ordering. Page fault
+ * handling code implies lock dependency:
+ *
+ * mmap_lock
+ *   -> sb_start_pagefault
+ */
+static inline void sb_start_pagefault(struct super_block *sb)
+{
+	__sb_start_write(sb, SB_FREEZE_PAGEFAULT);
+}
+
+/**
+ * sb_start_intwrite - get write access to a superblock for internal fs purposes
+ * @sb: the super we write to
+ *
+ * This is the third level of protection against filesystem freezing. It is
+ * free for use by a filesystem. The only requirement is that it must rank
+ * below sb_start_pagefault.
+ *
+ * For example filesystem can call sb_start_intwrite() when starting a
+ * transaction which somewhat eases handling of freezing for internal sources
+ * of filesystem changes (internal fs threads, discarding preallocation on file
+ * close, etc.).
+ */
+static inline void sb_start_intwrite(struct super_block *sb)
+{
+	__sb_start_write(sb, SB_FREEZE_FS);
+}
+
+static inline bool sb_start_intwrite_trylock(struct super_block *sb)
+{
+	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
+}
+
+static inline bool sb_rdonly(const struct super_block *sb)
+{
+	return sb->s_flags & SB_RDONLY;
+}
+
+static inline bool sb_is_blkdev_sb(struct super_block *sb)
+{
+	return IS_ENABLED(CONFIG_BLOCK) && sb == blockdev_superblock;
+}
+
+#if IS_ENABLED(CONFIG_UNICODE)
+static inline struct unicode_map *sb_encoding(const struct super_block *sb)
+{
+	return sb->s_encoding;
+}
+
+/* Compare if two super blocks have the same encoding and flags */
+static inline bool sb_same_encoding(const struct super_block *sb1,
+				    const struct super_block *sb2)
+{
+	if (sb1->s_encoding == sb2->s_encoding)
+		return true;
+
+	return (sb1->s_encoding && sb2->s_encoding &&
+		(sb1->s_encoding->version == sb2->s_encoding->version) &&
+		(sb1->s_encoding_flags == sb2->s_encoding_flags));
+}
+#else
+static inline struct unicode_map *sb_encoding(const struct super_block *sb)
+{
+	return NULL;
+}
+
+static inline bool sb_same_encoding(const struct super_block *sb1,
+				    const struct super_block *sb2)
+{
+	return true;
+}
+#endif
+
+static inline bool sb_has_encoding(const struct super_block *sb)
+{
+	return !!sb_encoding(sb);
+}
+
+int sb_set_blocksize(struct super_block *sb, int size);
+int __must_check sb_min_blocksize(struct super_block *sb, int size);
+
+int freeze_super(struct super_block *super, enum freeze_holder who,
+		 const void *freeze_owner);
+int thaw_super(struct super_block *super, enum freeze_holder who,
+	       const void *freeze_owner);
+
+#endif /* _LINUX_FS_SUPER_H */