diff options
| -rw-r--r-- | fs/internal.h | 1 | ||||
| -rw-r--r-- | fs/namespace.c | 40 | ||||
| -rw-r--r-- | fs/super.c | 22 | ||||
| -rw-r--r-- | include/linux/fs.h | 3 |
4 files changed, 61 insertions, 5 deletions
diff --git a/fs/internal.h b/fs/internal.h index 2523a4029452..9962c59ba280 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -52,6 +52,7 @@ extern int finish_automount(struct vfsmount *, struct path *); extern void mnt_make_longterm(struct vfsmount *); extern void mnt_make_shortterm(struct vfsmount *); +extern int sb_prepare_remount_readonly(struct super_block *); extern void __init mnt_init(void); diff --git a/fs/namespace.c b/fs/namespace.c index 145217b088d1..98ebc78b21ab 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -273,6 +273,15 @@ static unsigned int mnt_get_writers(struct mount *mnt) #endif } +static int mnt_is_readonly(struct vfsmount *mnt) +{ + if (mnt->mnt_sb->s_readonly_remount) + return 1; + /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ + smp_rmb(); + return __mnt_is_readonly(mnt); +} + /* * Most r/o checks on a fs are for operations that take * discrete amounts of time, like a write() or unlink(). @@ -312,7 +321,7 @@ int mnt_want_write(struct vfsmount *m) * MNT_WRITE_HOLD is cleared. */ smp_rmb(); - if (__mnt_is_readonly(m)) { + if (mnt_is_readonly(m)) { mnt_dec_writers(mnt); ret = -EROFS; goto out; @@ -435,6 +444,35 @@ static void __mnt_unmake_readonly(struct mount *mnt) br_write_unlock(vfsmount_lock); } +int sb_prepare_remount_readonly(struct super_block *sb) +{ + struct mount *mnt; + int err = 0; + + br_write_lock(vfsmount_lock); + list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { + if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { + mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; + smp_mb(); + if (mnt_get_writers(mnt) > 0) { + err = -EBUSY; + break; + } + } + } + if (!err) { + sb->s_readonly_remount = 1; + smp_wmb(); + } + 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; + } + br_write_unlock(vfsmount_lock); + + return err; +} + static void free_vfsmnt(struct mount *mnt) { kfree(mnt->mnt_devname); diff --git a/fs/super.c b/fs/super.c index 993ca8f128d6..6acc02237e3e 100644 --- a/fs/super.c +++ b/fs/super.c @@ -723,23 +723,33 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force) /* If we are remounting RDONLY and current sb is read/write, make sure there are no rw files opened */ if (remount_ro) { - if (force) + if (force) { mark_files_ro(sb); - else if (!fs_may_remount_ro(sb)) - return -EBUSY; + } else { + retval = sb_prepare_remount_readonly(sb); + if (retval) + return retval; + + retval = -EBUSY; + if (!fs_may_remount_ro(sb)) + goto cancel_readonly; + } } if (sb->s_op->remount_fs) { retval = sb->s_op->remount_fs(sb, &flags, data); if (retval) { if (!force) - return retval; + goto cancel_readonly; /* If forced remount, go ahead despite any errors */ WARN(1, "forced remount of a %s fs returned %i\n", sb->s_type->name, retval); } } sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK); + /* Needs to be ordered wrt mnt_is_readonly() */ + smp_wmb(); + sb->s_readonly_remount = 0; /* * Some filesystems modify their metadata via some other path than the @@ -752,6 +762,10 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force) if (remount_ro && sb->s_bdev) invalidate_bdev(sb->s_bdev); return 0; + +cancel_readonly: + sb->s_readonly_remount = 0; + return retval; } static void do_emergency_remount(struct work_struct *work) diff --git a/include/linux/fs.h b/include/linux/fs.h index 03385acd71e8..7b8a681b1ef4 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1482,6 +1482,9 @@ struct super_block { int cleancache_poolid; struct shrinker s_shrink; /* per-sb shrinker handle */ + + /* Being remounted read-only */ + int s_readonly_remount; }; /* superblock cache pruning functions */ |