diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/fs.h | 150 |
1 files changed, 143 insertions, 7 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 80c819cbe27..aefed9426b0 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -412,6 +412,7 @@ struct inodes_stat_t { #include <linux/shrinker.h> #include <linux/migrate_mode.h> #include <linux/uidgid.h> +#include <linux/lockdep.h> #include <asm/byteorder.h> @@ -1439,6 +1440,8 @@ extern void f_delown(struct file *filp); extern pid_t f_getown(struct file *filp); extern int send_sigurg(struct fown_struct *fown); +struct mm_struct; + /* * Umount options */ @@ -1452,6 +1455,32 @@ extern int send_sigurg(struct fown_struct *fown); extern struct list_head super_blocks; extern spinlock_t sb_lock; +/* Possible states of 'frozen' field */ +enum { + SB_UNFROZEN = 0, /* FS is unfrozen */ + SB_FREEZE_WRITE = 1, /* Writes, dir ops, ioctls frozen */ + SB_FREEZE_TRANS = 2, + SB_FREEZE_PAGEFAULT = 2, /* Page faults stopped as well */ + SB_FREEZE_FS = 3, /* For internal FS use (e.g. to stop + * internal threads if needed) */ + SB_FREEZE_COMPLETE = 4, /* ->freeze_fs finished successfully */ +}; + +#define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1) + +struct sb_writers { + /* Counters for counting writers at each level */ + struct percpu_counter counter[SB_FREEZE_LEVELS]; + wait_queue_head_t wait; /* queue for waiting for + writers / faults to finish */ + int frozen; /* Is sb frozen? */ + wait_queue_head_t wait_unfrozen; /* queue for waiting for + sb to be thawed */ +#ifdef CONFIG_DEBUG_LOCK_ALLOC + struct lockdep_map lock_map[SB_FREEZE_LEVELS]; +#endif +}; + struct super_block { struct list_head s_list; /* Keep this first */ dev_t s_dev; /* search index; _not_ kdev_t */ @@ -1501,6 +1530,7 @@ struct super_block { int s_frozen; wait_queue_head_t s_wait_unfrozen; + struct sb_writers s_writers; char s_id[32]; /* Informational name */ u8 s_uuid[16]; /* UUID */ @@ -1555,14 +1585,119 @@ extern struct timespec current_fs_time(struct super_block *sb); /* * Snapshotting support. */ -enum { - SB_UNFROZEN = 0, - SB_FREEZE_WRITE = 1, - SB_FREEZE_TRANS = 2, -}; +/* Will go away when all users are converted */ +#define vfs_check_frozen(sb, level) do { } while (0) + +void __sb_end_write(struct super_block *sb, int level); +int __sb_start_write(struct super_block *sb, int level, bool wait); + +/** + * 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_mutex (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, true); +} + +static inline int sb_start_write_trylock(struct super_block *sb) +{ + return __sb_start_write(sb, SB_FREEZE_WRITE, false); +} + +/** + * 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_sem in lock ordering. Page fault + * handling code implies lock dependency: + * + * mmap_sem + * -> sb_start_pagefault + */ +static inline void sb_start_pagefault(struct super_block *sb) +{ + __sb_start_write(sb, SB_FREEZE_PAGEFAULT, true); +} + +/* + * 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, true); +} -#define vfs_check_frozen(sb, level) \ - wait_event((sb)->s_wait_unfrozen, ((sb)->s_frozen < (level))) extern bool inode_owner_or_capable(const struct inode *inode); @@ -1886,6 +2021,7 @@ struct file_system_type { struct lock_class_key s_lock_key; struct lock_class_key s_umount_key; struct lock_class_key s_vfs_rename_key; + struct lock_class_key s_writers_key[SB_FREEZE_LEVELS]; struct lock_class_key i_lock_key; struct lock_class_key i_mutex_key; |