diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 54847db5b819..5ba1eca6f720 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -309,9 +309,16 @@ static unsigned int mnt_get_writers(struct mount *mnt) static int mnt_is_readonly(struct vfsmount *mnt) { - if (mnt->mnt_sb->s_readonly_remount) + if (READ_ONCE(mnt->mnt_sb->s_readonly_remount)) return 1; - /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ + /* + * The barrier pairs with the barrier in sb_start_ro_state_change() + * making sure if we don't see s_readonly_remount set yet, we also will + * not see any superblock / mount flag changes done by remount. + * It also pairs with the barrier in sb_end_ro_state_change() + * assuring that if we see s_readonly_remount already cleared, we will + * see the values of superblock / mount flags updated by remount. + */ smp_rmb(); return __mnt_is_readonly(mnt); } @@ -364,9 +371,11 @@ int __mnt_want_write(struct vfsmount *m) } } /* - * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will - * be set to match its requirements. So we must not load that until - * MNT_WRITE_HOLD is cleared. + * The barrier pairs with the barrier sb_start_ro_state_change() making + * sure that if we see MNT_WRITE_HOLD cleared, we will also see + * s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in + * mnt_is_readonly() and bail in case we are racing with remount + * read-only. */ smp_rmb(); if (mnt_is_readonly(m)) { @@ -588,10 +597,8 @@ int sb_prepare_remount_readonly(struct super_block *sb) if (!err && atomic_long_read(&sb->s_remove_count)) err = -EBUSY; - if (!err) { - sb->s_readonly_remount = 1; - smp_wmb(); - } + if (!err) + sb_start_ro_state_change(sb); list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |