diff options
Diffstat (limited to 'fs/internal.h')
| -rw-r--r-- | fs/internal.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/fs/internal.h b/fs/internal.h index bd3b2810a36b..b916b84809f3 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -121,6 +121,47 @@ extern bool mount_capable(struct fs_context *); int sb_init_dio_done_wq(struct super_block *sb); /* + * Prepare superblock for changing its read-only state (i.e., either remount + * read-write superblock read-only or vice versa). After this function returns + * mnt_is_readonly() will return true for any mount of the superblock if its + * caller is able to observe any changes done by the remount. This holds until + * sb_end_ro_state_change() is called. + */ +static inline void sb_start_ro_state_change(struct super_block *sb) +{ + WRITE_ONCE(sb->s_readonly_remount, 1); + /* + * For RO->RW transition, the barrier pairs with the barrier in + * mnt_is_readonly() making sure if mnt_is_readonly() sees SB_RDONLY + * cleared, it will see s_readonly_remount set. + * For RW->RO transition, the barrier pairs with the barrier in + * __mnt_want_write() before the mnt_is_readonly() check. The barrier + * makes sure if __mnt_want_write() sees MNT_WRITE_HOLD already + * cleared, it will see s_readonly_remount set. + */ + smp_wmb(); +} + +/* + * Ends section changing read-only state of the superblock. After this function + * returns if mnt_is_readonly() returns false, the caller will be able to + * observe all the changes remount did to the superblock. + */ +static inline void sb_end_ro_state_change(struct super_block *sb) +{ + /* + * This barrier provides release semantics that pairs with + * the smp_rmb() acquire semantics in mnt_is_readonly(). + * This barrier pair ensure that when mnt_is_readonly() sees + * 0 for sb->s_readonly_remount, it will also see all the + * preceding flag changes that were made during the RO state + * change. + */ + smp_wmb(); + WRITE_ONCE(sb->s_readonly_remount, 0); +} + +/* * open.c */ struct open_flags { |