1
linux/fs/super.c
Christian Brauner 2ae4db5647
fs: don't misleadingly warn during thaw operations
The block device may have been frozen before it was claimed by a
filesystem. Concurrently another process might try to mount that
frozen block device and has temporarily claimed the block device for
that purpose causing a concurrent fs_bdev_thaw() to end up here. The
mounter is already about to abort mounting because they still saw an
elevanted bdev->bd_fsfreeze_count so get_bdev_super() will return
NULL in that case.

For example, P1 calls dm_suspend() which calls into bdev_freeze() before
the block device has been claimed by the filesystem. This brings
bdev->bd_fsfreeze_count to 1 and no call into fs_bdev_freeze() is
required.

Now P2 tries to mount that frozen block device. It claims it and checks
bdev->bd_fsfreeze_count. As it's elevated it aborts mounting.

In the meantime P3 called dm_resume(). P3 sees that the block device is
already claimed by a filesystem and calls into fs_bdev_thaw().

P3 takes a passive reference and realizes that the filesystem isn't
ready yet. P3 puts itself to sleep to wait for the filesystem to become
ready.

P2 now puts the last active reference to the filesystem and marks it as
dying. P3 gets woken, sees that the filesystem is dying and
get_bdev_super() fails.

Fixes: 49ef8832fb ("bdev: implement freeze and thaw holder operations")
Cc: <stable@vger.kernel.org>
Reported-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20240611085210.GA1838544@mit.edu
Link: https://lore.kernel.org/r/20240613-lackmantel-einsehen-90f0d727358d@brauner
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-06-18 16:20:47 +02:00

2221 lines
58 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/super.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* super.c contains code to handle: - mount structures
* - super-block tables
* - filesystem drivers list
* - mount system call
* - umount system call
* - ustat system call
*
* GK 2/5/95 - Changed to support mounting the root fs via NFS
*
* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
* Added options to /proc/mounts:
* Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
*/
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/writeback.h> /* for the emergency remount stuff */
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
#include <linux/rculist_bl.h>
#include <linux/fscrypt.h>
#include <linux/fsnotify.h>
#include <linux/lockdep.h>
#include <linux/user_namespace.h>
#include <linux/fs_context.h>
#include <uapi/linux/mount.h>
#include "internal.h"
static int thaw_super_locked(struct super_block *sb, enum freeze_holder who);
static LIST_HEAD(super_blocks);
static DEFINE_SPINLOCK(sb_lock);
static char *sb_writers_name[SB_FREEZE_LEVELS] = {
"sb_writers",
"sb_pagefaults",
"sb_internal",
};
static inline void __super_lock(struct super_block *sb, bool excl)
{
if (excl)
down_write(&sb->s_umount);
else
down_read(&sb->s_umount);
}
static inline void super_unlock(struct super_block *sb, bool excl)
{
if (excl)
up_write(&sb->s_umount);
else
up_read(&sb->s_umount);
}
static inline void __super_lock_excl(struct super_block *sb)
{
__super_lock(sb, true);
}
static inline void super_unlock_excl(struct super_block *sb)
{
super_unlock(sb, true);
}
static inline void super_unlock_shared(struct super_block *sb)
{
super_unlock(sb, false);
}
static bool super_flags(const struct super_block *sb, unsigned int flags)
{
/*
* Pairs with smp_store_release() in super_wake() and ensures
* that we see @flags after we're woken.
*/
return smp_load_acquire(&sb->s_flags) & flags;
}
/**
* super_lock - wait for superblock to become ready and lock it
* @sb: superblock to wait for
* @excl: whether exclusive access is required
*
* If the superblock has neither passed through vfs_get_tree() or
* generic_shutdown_super() yet wait for it to happen. Either superblock
* creation will succeed and SB_BORN is set by vfs_get_tree() or we're
* woken and we'll see SB_DYING.
*
* The caller must have acquired a temporary reference on @sb->s_count.
*
* Return: The function returns true if SB_BORN was set and with
* s_umount held. The function returns false if SB_DYING was
* set and without s_umount held.
*/
static __must_check bool super_lock(struct super_block *sb, bool excl)
{
lockdep_assert_not_held(&sb->s_umount);
/* wait until the superblock is ready or dying */
wait_var_event(&sb->s_flags, super_flags(sb, SB_BORN | SB_DYING));
/* Don't pointlessly acquire s_umount. */
if (super_flags(sb, SB_DYING))
return false;
__super_lock(sb, excl);
/*
* Has gone through generic_shutdown_super() in the meantime.
* @sb->s_root is NULL and @sb->s_active is 0. No one needs to
* grab a reference to this. Tell them so.
*/
if (sb->s_flags & SB_DYING) {
super_unlock(sb, excl);
return false;
}
WARN_ON_ONCE(!(sb->s_flags & SB_BORN));
return true;
}
/* wait and try to acquire read-side of @sb->s_umount */
static inline bool super_lock_shared(struct super_block *sb)
{
return super_lock(sb, false);
}
/* wait and try to acquire write-side of @sb->s_umount */
static inline bool super_lock_excl(struct super_block *sb)
{
return super_lock(sb, true);
}
/* wake waiters */
#define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD)
static void super_wake(struct super_block *sb, unsigned int flag)
{
WARN_ON_ONCE((flag & ~SUPER_WAKE_FLAGS));
WARN_ON_ONCE(hweight32(flag & SUPER_WAKE_FLAGS) > 1);
/*
* Pairs with smp_load_acquire() in super_lock() to make sure
* all initializations in the superblock are seen by the user
* seeing SB_BORN sent.
*/
smp_store_release(&sb->s_flags, sb->s_flags | flag);
/*
* Pairs with the barrier in prepare_to_wait_event() to make sure
* ___wait_var_event() either sees SB_BORN set or
* waitqueue_active() check in wake_up_var() sees the waiter.
*/
smp_mb();
wake_up_var(&sb->s_flags);
}
/*
* One thing we have to be careful of with a per-sb shrinker is that we don't
* drop the last active reference to the superblock from within the shrinker.
* If that happens we could trigger unregistering the shrinker from within the
* shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
* take a passive reference to the superblock to avoid this from occurring.
*/
static unsigned long super_cache_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct super_block *sb;
long fs_objects = 0;
long total_objects;
long freed = 0;
long dentries;
long inodes;
sb = shrink->private_data;
/*
* Deadlock avoidance. We may hold various FS locks, and we don't want
* to recurse into the FS that called us in clear_inode() and friends..
*/
if (!(sc->gfp_mask & __GFP_FS))
return SHRINK_STOP;
if (!super_trylock_shared(sb))
return SHRINK_STOP;
if (sb->s_op->nr_cached_objects)
fs_objects = sb->s_op->nr_cached_objects(sb, sc);
inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects = dentries + inodes + fs_objects + 1;
if (!total_objects)
total_objects = 1;
/* proportion the scan between the caches */
dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
/*
* prune the dcache first as the icache is pinned by it, then
* prune the icache, followed by the filesystem specific caches
*
* Ensure that we always scan at least one object - memcg kmem
* accounting uses this to fully empty the caches.
*/
sc->nr_to_scan = dentries + 1;
freed = prune_dcache_sb(sb, sc);
sc->nr_to_scan = inodes + 1;
freed += prune_icache_sb(sb, sc);
if (fs_objects) {
sc->nr_to_scan = fs_objects + 1;
freed += sb->s_op->free_cached_objects(sb, sc);
}
super_unlock_shared(sb);
return freed;
}
static unsigned long super_cache_count(struct shrinker *shrink,
struct shrink_control *sc)
{
struct super_block *sb;
long total_objects = 0;
sb = shrink->private_data;
/*
* We don't call super_trylock_shared() here as it is a scalability
* bottleneck, so we're exposed to partial setup state. The shrinker
* rwsem does not protect filesystem operations backing
* list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can
* change between super_cache_count and super_cache_scan, so we really
* don't need locks here.
*
* However, if we are currently mounting the superblock, the underlying
* filesystem might be in a state of partial construction and hence it
* is dangerous to access it. super_trylock_shared() uses a SB_BORN check
* to avoid this situation, so do the same here. The memory barrier is
* matched with the one in mount_fs() as we don't hold locks here.
*/
if (!(sb->s_flags & SB_BORN))
return 0;
smp_rmb();
if (sb->s_op && sb->s_op->nr_cached_objects)
total_objects = sb->s_op->nr_cached_objects(sb, sc);
total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
if (!total_objects)
return SHRINK_EMPTY;
total_objects = vfs_pressure_ratio(total_objects);
return total_objects;
}
static void destroy_super_work(struct work_struct *work)
{
struct super_block *s = container_of(work, struct super_block,
destroy_work);
fsnotify_sb_free(s);
security_sb_free(s);
put_user_ns(s->s_user_ns);
kfree(s->s_subtype);
for (int i = 0; i < SB_FREEZE_LEVELS; i++)
percpu_free_rwsem(&s->s_writers.rw_sem[i]);
kfree(s);
}
static void destroy_super_rcu(struct rcu_head *head)
{
struct super_block *s = container_of(head, struct super_block, rcu);
INIT_WORK(&s->destroy_work, destroy_super_work);
schedule_work(&s->destroy_work);
}
/* Free a superblock that has never been seen by anyone */
static void destroy_unused_super(struct super_block *s)
{
if (!s)
return;
super_unlock_excl(s);
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
shrinker_free(s->s_shrink);
/* no delays needed */
destroy_super_work(&s->destroy_work);
}
/**
* alloc_super - create new superblock
* @type: filesystem type superblock should belong to
* @flags: the mount flags
* @user_ns: User namespace for the super_block
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
static struct super_block *alloc_super(struct file_system_type *type, int flags,
struct user_namespace *user_ns)
{
struct super_block *s = kzalloc(sizeof(struct super_block), GFP_KERNEL);
static const struct super_operations default_op;
int i;
if (!s)
return NULL;
INIT_LIST_HEAD(&s->s_mounts);
s->s_user_ns = get_user_ns(user_ns);
init_rwsem(&s->s_umount);
lockdep_set_class(&s->s_umount, &type->s_umount_key);
/*
* sget() can have s_umount recursion.
*
* When it cannot find a suitable sb, it allocates a new
* one (this one), and tries again to find a suitable old
* one.
*
* In case that succeeds, it will acquire the s_umount
* lock of the old one. Since these are clearly distrinct
* locks, and this object isn't exposed yet, there's no
* risk of deadlocks.
*
* Annotate this by putting this lock in a different
* subclass.
*/
down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
if (security_sb_alloc(s))
goto fail;
for (i = 0; i < SB_FREEZE_LEVELS; i++) {
if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
sb_writers_name[i],
&type->s_writers_key[i]))
goto fail;
}
s->s_bdi = &noop_backing_dev_info;
s->s_flags = flags;
if (s->s_user_ns != &init_user_ns)
s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_roots);
mutex_init(&s->s_sync_lock);
INIT_LIST_HEAD(&s->s_inodes);
spin_lock_init(&s->s_inode_list_lock);
INIT_LIST_HEAD(&s->s_inodes_wb);
spin_lock_init(&s->s_inode_wblist_lock);
s->s_count = 1;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
init_rwsem(&s->s_dquot.dqio_sem);
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
s->s_time_min = TIME64_MIN;
s->s_time_max = TIME64_MAX;
s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
"sb-%s", type->name);
if (!s->s_shrink)
goto fail;
s->s_shrink->scan_objects = super_cache_scan;
s->s_shrink->count_objects = super_cache_count;
s->s_shrink->batch = 1024;
s->s_shrink->private_data = s;
if (list_lru_init_memcg(&s->s_dentry_lru, s->s_shrink))
goto fail;
if (list_lru_init_memcg(&s->s_inode_lru, s->s_shrink))
goto fail;
return s;
fail:
destroy_unused_super(s);
return NULL;
}
/* Superblock refcounting */
/*
* Drop a superblock's refcount. The caller must hold sb_lock.
*/
static void __put_super(struct super_block *s)
{
if (!--s->s_count) {
list_del_init(&s->s_list);
WARN_ON(s->s_dentry_lru.node);
WARN_ON(s->s_inode_lru.node);
WARN_ON(!list_empty(&s->s_mounts));
call_rcu(&s->rcu, destroy_super_rcu);
}
}
/**
* put_super - drop a temporary reference to superblock
* @sb: superblock in question
*
* Drops a temporary reference, frees superblock if there's no
* references left.
*/
void put_super(struct super_block *sb)
{
spin_lock(&sb_lock);
__put_super(sb);
spin_unlock(&sb_lock);
}
static void kill_super_notify(struct super_block *sb)
{
lockdep_assert_not_held(&sb->s_umount);
/* already notified earlier */
if (sb->s_flags & SB_DEAD)
return;
/*
* Remove it from @fs_supers so it isn't found by new
* sget{_fc}() walkers anymore. Any concurrent mounter still
* managing to grab a temporary reference is guaranteed to
* already see SB_DYING and will wait until we notify them about
* SB_DEAD.
*/
spin_lock(&sb_lock);
hlist_del_init(&sb->s_instances);
spin_unlock(&sb_lock);
/*
* Let concurrent mounts know that this thing is really dead.
* We don't need @sb->s_umount here as every concurrent caller
* will see SB_DYING and either discard the superblock or wait
* for SB_DEAD.
*/
super_wake(sb, SB_DEAD);
}
/**
* deactivate_locked_super - drop an active reference to superblock
* @s: superblock to deactivate
*
* Drops an active reference to superblock, converting it into a temporary
* one if there is no other active references left. In that case we
* tell fs driver to shut it down and drop the temporary reference we
* had just acquired.
*
* Caller holds exclusive lock on superblock; that lock is released.
*/
void deactivate_locked_super(struct super_block *s)
{
struct file_system_type *fs = s->s_type;
if (atomic_dec_and_test(&s->s_active)) {
shrinker_free(s->s_shrink);
fs->kill_sb(s);
kill_super_notify(s);
/*
* Since list_lru_destroy() may sleep, we cannot call it from
* put_super(), where we hold the sb_lock. Therefore we destroy
* the lru lists right now.
*/
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
put_filesystem(fs);
put_super(s);
} else {
super_unlock_excl(s);
}
}
EXPORT_SYMBOL(deactivate_locked_super);
/**
* deactivate_super - drop an active reference to superblock
* @s: superblock to deactivate
*
* Variant of deactivate_locked_super(), except that superblock is *not*
* locked by caller. If we are going to drop the final active reference,
* lock will be acquired prior to that.
*/
void deactivate_super(struct super_block *s)
{
if (!atomic_add_unless(&s->s_active, -1, 1)) {
__super_lock_excl(s);
deactivate_locked_super(s);
}
}
EXPORT_SYMBOL(deactivate_super);
/**
* grab_super - acquire an active reference to a superblock
* @sb: superblock to acquire
*
* Acquire a temporary reference on a superblock and try to trade it for
* an active reference. This is used in sget{_fc}() to wait for a
* superblock to either become SB_BORN or for it to pass through
* sb->kill() and be marked as SB_DEAD.
*
* Return: This returns true if an active reference could be acquired,
* false if not.
*/
static bool grab_super(struct super_block *sb)
{
bool locked;
sb->s_count++;
spin_unlock(&sb_lock);
locked = super_lock_excl(sb);
if (locked) {
if (atomic_inc_not_zero(&sb->s_active)) {
put_super(sb);
return true;
}
super_unlock_excl(sb);
}
wait_var_event(&sb->s_flags, super_flags(sb, SB_DEAD));
put_super(sb);
return false;
}
/*
* super_trylock_shared - try to grab ->s_umount shared
* @sb: reference we are trying to grab
*
* Try to prevent fs shutdown. This is used in places where we
* cannot take an active reference but we need to ensure that the
* filesystem is not shut down while we are working on it. It returns
* false if we cannot acquire s_umount or if we lose the race and
* filesystem already got into shutdown, and returns true with the s_umount
* lock held in read mode in case of success. On successful return,
* the caller must drop the s_umount lock when done.
*
* Note that unlike get_super() et.al. this one does *not* bump ->s_count.
* The reason why it's safe is that we are OK with doing trylock instead
* of down_read(). There's a couple of places that are OK with that, but
* it's very much not a general-purpose interface.
*/
bool super_trylock_shared(struct super_block *sb)
{
if (down_read_trylock(&sb->s_umount)) {
if (!(sb->s_flags & SB_DYING) && sb->s_root &&
(sb->s_flags & SB_BORN))
return true;
super_unlock_shared(sb);
}
return false;
}
/**
* retire_super - prevents superblock from being reused
* @sb: superblock to retire
*
* The function marks superblock to be ignored in superblock test, which
* prevents it from being reused for any new mounts. If the superblock has
* a private bdi, it also unregisters it, but doesn't reduce the refcount
* of the superblock to prevent potential races. The refcount is reduced
* by generic_shutdown_super(). The function can not be called
* concurrently with generic_shutdown_super(). It is safe to call the
* function multiple times, subsequent calls have no effect.
*
* The marker will affect the re-use only for block-device-based
* superblocks. Other superblocks will still get marked if this function
* is used, but that will not affect their reusability.
*/
void retire_super(struct super_block *sb)
{
WARN_ON(!sb->s_bdev);
__super_lock_excl(sb);
if (sb->s_iflags & SB_I_PERSB_BDI) {
bdi_unregister(sb->s_bdi);
sb->s_iflags &= ~SB_I_PERSB_BDI;
}
sb->s_iflags |= SB_I_RETIRED;
super_unlock_excl(sb);
}
EXPORT_SYMBOL(retire_super);
/**
* generic_shutdown_super - common helper for ->kill_sb()
* @sb: superblock to kill
*
* generic_shutdown_super() does all fs-independent work on superblock
* shutdown. Typical ->kill_sb() should pick all fs-specific objects
* that need destruction out of superblock, call generic_shutdown_super()
* and release aforementioned objects. Note: dentries and inodes _are_
* taken care of and do not need specific handling.
*
* Upon calling this function, the filesystem may no longer alter or
* rearrange the set of dentries belonging to this super_block, nor may it
* change the attachments of dentries to inodes.
*/
void generic_shutdown_super(struct super_block *sb)
{
const struct super_operations *sop = sb->s_op;
if (sb->s_root) {
shrink_dcache_for_umount(sb);
sync_filesystem(sb);
sb->s_flags &= ~SB_ACTIVE;
cgroup_writeback_umount();
/* Evict all inodes with zero refcount. */
evict_inodes(sb);
/*
* Clean up and evict any inodes that still have references due
* to fsnotify or the security policy.
*/
fsnotify_sb_delete(sb);
security_sb_delete(sb);
if (sb->s_dio_done_wq) {
destroy_workqueue(sb->s_dio_done_wq);
sb->s_dio_done_wq = NULL;
}
if (sop->put_super)
sop->put_super(sb);
/*
* Now that all potentially-encrypted inodes have been evicted,
* the fscrypt keyring can be destroyed.
*/
fscrypt_destroy_keyring(sb);
if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
"VFS: Busy inodes after unmount of %s (%s)",
sb->s_id, sb->s_type->name)) {
/*
* Adding a proper bailout path here would be hard, but
* we can at least make it more likely that a later
* iput_final() or such crashes cleanly.
*/
struct inode *inode;
spin_lock(&sb->s_inode_list_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
inode->i_op = VFS_PTR_POISON;
inode->i_sb = VFS_PTR_POISON;
inode->i_mapping = VFS_PTR_POISON;
}
spin_unlock(&sb->s_inode_list_lock);
}
}
/*
* Broadcast to everyone that grabbed a temporary reference to this
* superblock before we removed it from @fs_supers that the superblock
* is dying. Every walker of @fs_supers outside of sget{_fc}() will now
* discard this superblock and treat it as dead.
*
* We leave the superblock on @fs_supers so it can be found by
* sget{_fc}() until we passed sb->kill_sb().
*/
super_wake(sb, SB_DYING);
super_unlock_excl(sb);
if (sb->s_bdi != &noop_backing_dev_info) {
if (sb->s_iflags & SB_I_PERSB_BDI)
bdi_unregister(sb->s_bdi);
bdi_put(sb->s_bdi);
sb->s_bdi = &noop_backing_dev_info;
}
}
EXPORT_SYMBOL(generic_shutdown_super);
bool mount_capable(struct fs_context *fc)
{
if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
return capable(CAP_SYS_ADMIN);
else
return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
}
/**
* sget_fc - Find or create a superblock
* @fc: Filesystem context.
* @test: Comparison callback
* @set: Setup callback
*
* Create a new superblock or find an existing one.
*
* The @test callback is used to find a matching existing superblock.
* Whether or not the requested parameters in @fc are taken into account
* is specific to the @test callback that is used. They may even be
* completely ignored.
*
* If an extant superblock is matched, it will be returned unless:
*
* (1) the namespace the filesystem context @fc and the extant
* superblock's namespace differ
*
* (2) the filesystem context @fc has requested that reusing an extant
* superblock is not allowed
*
* In both cases EBUSY will be returned.
*
* If no match is made, a new superblock will be allocated and basic
* initialisation will be performed (s_type, s_fs_info and s_id will be
* set and the @set callback will be invoked), the superblock will be
* published and it will be returned in a partially constructed state
* with SB_BORN and SB_ACTIVE as yet unset.
*
* Return: On success, an extant or newly created superblock is
* returned. On failure an error pointer is returned.
*/
struct super_block *sget_fc(struct fs_context *fc,
int (*test)(struct super_block *, struct fs_context *),
int (*set)(struct super_block *, struct fs_context *))
{
struct super_block *s = NULL;
struct super_block *old;
struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
int err;
retry:
spin_lock(&sb_lock);
if (test) {
hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
if (test(old, fc))
goto share_extant_sb;
}
}
if (!s) {
spin_unlock(&sb_lock);
s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
}
s->s_fs_info = fc->s_fs_info;
err = set(s, fc);
if (err) {
s->s_fs_info = NULL;
spin_unlock(&sb_lock);
destroy_unused_super(s);
return ERR_PTR(err);
}
fc->s_fs_info = NULL;
s->s_type = fc->fs_type;
s->s_iflags |= fc->s_iflags;
strscpy(s->s_id, s->s_type->name, sizeof(s->s_id));
/*
* Make the superblock visible on @super_blocks and @fs_supers.
* It's in a nascent state and users should wait on SB_BORN or
* SB_DYING to be set.
*/
list_add_tail(&s->s_list, &super_blocks);
hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
spin_unlock(&sb_lock);
get_filesystem(s->s_type);
shrinker_register(s->s_shrink);
return s;
share_extant_sb:
if (user_ns != old->s_user_ns || fc->exclusive) {
spin_unlock(&sb_lock);
destroy_unused_super(s);
if (fc->exclusive)
warnfc(fc, "reusing existing filesystem not allowed");
else
warnfc(fc, "reusing existing filesystem in another namespace not allowed");
return ERR_PTR(-EBUSY);
}
if (!grab_super(old))
goto retry;
destroy_unused_super(s);
return old;
}
EXPORT_SYMBOL(sget_fc);
/**
* sget - find or create a superblock
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
* @flags: mount flags
* @data: argument to each of them
*/
struct super_block *sget(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
int flags,
void *data)
{
struct user_namespace *user_ns = current_user_ns();
struct super_block *s = NULL;
struct super_block *old;
int err;
/* We don't yet pass the user namespace of the parent
* mount through to here so always use &init_user_ns
* until that changes.
*/
if (flags & SB_SUBMOUNT)
user_ns = &init_user_ns;
retry:
spin_lock(&sb_lock);
if (test) {
hlist_for_each_entry(old, &type->fs_supers, s_instances) {
if (!test(old, data))
continue;
if (user_ns != old->s_user_ns) {
spin_unlock(&sb_lock);
destroy_unused_super(s);
return ERR_PTR(-EBUSY);
}
if (!grab_super(old))
goto retry;
destroy_unused_super(s);
return old;
}
}
if (!s) {
spin_unlock(&sb_lock);
s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
}
err = set(s, data);
if (err) {
spin_unlock(&sb_lock);
destroy_unused_super(s);
return ERR_PTR(err);
}
s->s_type = type;
strscpy(s->s_id, type->name, sizeof(s->s_id));
list_add_tail(&s->s_list, &super_blocks);
hlist_add_head(&s->s_instances, &type->fs_supers);
spin_unlock(&sb_lock);
get_filesystem(type);
shrinker_register(s->s_shrink);
return s;
}
EXPORT_SYMBOL(sget);
void drop_super(struct super_block *sb)
{
super_unlock_shared(sb);
put_super(sb);
}
EXPORT_SYMBOL(drop_super);
void drop_super_exclusive(struct super_block *sb)
{
super_unlock_excl(sb);
put_super(sb);
}
EXPORT_SYMBOL(drop_super_exclusive);
static void __iterate_supers(void (*f)(struct super_block *))
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (super_flags(sb, SB_DYING))
continue;
sb->s_count++;
spin_unlock(&sb_lock);
f(sb);
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
/**
* iterate_supers - call function for all active superblocks
* @f: function to call
* @arg: argument to pass to it
*
* Scans the superblock list and calls given function, passing it
* locked superblock and given argument.
*/
void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
bool locked;
sb->s_count++;
spin_unlock(&sb_lock);
locked = super_lock_shared(sb);
if (locked) {
if (sb->s_root)
f(sb, arg);
super_unlock_shared(sb);
}
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
/**
* iterate_supers_type - call function for superblocks of given type
* @type: fs type
* @f: function to call
* @arg: argument to pass to it
*
* Scans the superblock list and calls given function, passing it
* locked superblock and given argument.
*/
void iterate_supers_type(struct file_system_type *type,
void (*f)(struct super_block *, void *), void *arg)
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
bool locked;
sb->s_count++;
spin_unlock(&sb_lock);
locked = super_lock_shared(sb);
if (locked) {
if (sb->s_root)
f(sb, arg);
super_unlock_shared(sb);
}
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
EXPORT_SYMBOL(iterate_supers_type);
struct super_block *user_get_super(dev_t dev, bool excl)
{
struct super_block *sb;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (sb->s_dev == dev) {
bool locked;
sb->s_count++;
spin_unlock(&sb_lock);
/* still alive? */
locked = super_lock(sb, excl);
if (locked) {
if (sb->s_root)
return sb;
super_unlock(sb, excl);
}
/* nope, got unmounted */
spin_lock(&sb_lock);
__put_super(sb);
break;
}
}
spin_unlock(&sb_lock);
return NULL;
}
/**
* reconfigure_super - asks filesystem to change superblock parameters
* @fc: The superblock and configuration
*
* Alters the configuration parameters of a live superblock.
*/
int reconfigure_super(struct fs_context *fc)
{
struct super_block *sb = fc->root->d_sb;
int retval;
bool remount_ro = false;
bool remount_rw = false;
bool force = fc->sb_flags & SB_FORCE;
if (fc->sb_flags_mask & ~MS_RMT_MASK)
return -EINVAL;
if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
retval = security_sb_remount(sb, fc->security);
if (retval)
return retval;
if (fc->sb_flags_mask & SB_RDONLY) {
#ifdef CONFIG_BLOCK
if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
bdev_read_only(sb->s_bdev))
return -EACCES;
#endif
remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb);
remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
}
if (remount_ro) {
if (!hlist_empty(&sb->s_pins)) {
super_unlock_excl(sb);
group_pin_kill(&sb->s_pins);
__super_lock_excl(sb);
if (!sb->s_root)
return 0;
if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
remount_ro = !sb_rdonly(sb);
}
}
shrink_dcache_sb(sb);
/* If we are reconfiguring to RDONLY and current sb is read/write,
* make sure there are no files open for writing.
*/
if (remount_ro) {
if (force) {
sb_start_ro_state_change(sb);
} else {
retval = sb_prepare_remount_readonly(sb);
if (retval)
return retval;
}
} else if (remount_rw) {
/*
* Protect filesystem's reconfigure code from writes from
* userspace until reconfigure finishes.
*/
sb_start_ro_state_change(sb);
}
if (fc->ops->reconfigure) {
retval = fc->ops->reconfigure(fc);
if (retval) {
if (!force)
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);
}
}
WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
(fc->sb_flags & fc->sb_flags_mask)));
sb_end_ro_state_change(sb);
/*
* Some filesystems modify their metadata via some other path than the
* bdev buffer cache (eg. use a private mapping, or directories in
* pagecache, etc). Also file data modifications go via their own
* mappings. So If we try to mount readonly then copy the filesystem
* from bdev, we could get stale data, so invalidate it to give a best
* effort at coherency.
*/
if (remount_ro && sb->s_bdev)
invalidate_bdev(sb->s_bdev);
return 0;
cancel_readonly:
sb_end_ro_state_change(sb);
return retval;
}
static void do_emergency_remount_callback(struct super_block *sb)
{
bool locked = super_lock_excl(sb);
if (locked && sb->s_root && sb->s_bdev && !sb_rdonly(sb)) {
struct fs_context *fc;
fc = fs_context_for_reconfigure(sb->s_root,
SB_RDONLY | SB_FORCE, SB_RDONLY);
if (!IS_ERR(fc)) {
if (parse_monolithic_mount_data(fc, NULL) == 0)
(void)reconfigure_super(fc);
put_fs_context(fc);
}
}
if (locked)
super_unlock_excl(sb);
}
static void do_emergency_remount(struct work_struct *work)
{
__iterate_supers(do_emergency_remount_callback);
kfree(work);
printk("Emergency Remount complete\n");
}
void emergency_remount(void)
{
struct work_struct *work;
work = kmalloc(sizeof(*work), GFP_ATOMIC);
if (work) {
INIT_WORK(work, do_emergency_remount);
schedule_work(work);
}
}
static void do_thaw_all_callback(struct super_block *sb)
{
bool locked = super_lock_excl(sb);
if (locked && sb->s_root) {
if (IS_ENABLED(CONFIG_BLOCK))
while (sb->s_bdev && !bdev_thaw(sb->s_bdev))
pr_warn("Emergency Thaw on %pg\n", sb->s_bdev);
thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE);
return;
}
if (locked)
super_unlock_excl(sb);
}
static void do_thaw_all(struct work_struct *work)
{
__iterate_supers(do_thaw_all_callback);
kfree(work);
printk(KERN_WARNING "Emergency Thaw complete\n");
}
/**
* emergency_thaw_all -- forcibly thaw every frozen filesystem
*
* Used for emergency unfreeze of all filesystems via SysRq
*/
void emergency_thaw_all(void)
{
struct work_struct *work;
work = kmalloc(sizeof(*work), GFP_ATOMIC);
if (work) {
INIT_WORK(work, do_thaw_all);
schedule_work(work);
}
}
static DEFINE_IDA(unnamed_dev_ida);
/**
* get_anon_bdev - Allocate a block device for filesystems which don't have one.
* @p: Pointer to a dev_t.
*
* Filesystems which don't use real block devices can call this function
* to allocate a virtual block device.
*
* Context: Any context. Frequently called while holding sb_lock.
* Return: 0 on success, -EMFILE if there are no anonymous bdevs left
* or -ENOMEM if memory allocation failed.
*/
int get_anon_bdev(dev_t *p)
{
int dev;
/*
* Many userspace utilities consider an FSID of 0 invalid.
* Always return at least 1 from get_anon_bdev.
*/
dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
GFP_ATOMIC);
if (dev == -ENOSPC)
dev = -EMFILE;
if (dev < 0)
return dev;
*p = MKDEV(0, dev);
return 0;
}
EXPORT_SYMBOL(get_anon_bdev);
void free_anon_bdev(dev_t dev)
{
ida_free(&unnamed_dev_ida, MINOR(dev));
}
EXPORT_SYMBOL(free_anon_bdev);
int set_anon_super(struct super_block *s, void *data)
{
return get_anon_bdev(&s->s_dev);
}
EXPORT_SYMBOL(set_anon_super);
void kill_anon_super(struct super_block *sb)
{
dev_t dev = sb->s_dev;
generic_shutdown_super(sb);
kill_super_notify(sb);
free_anon_bdev(dev);
}
EXPORT_SYMBOL(kill_anon_super);
void kill_litter_super(struct super_block *sb)
{
if (sb->s_root)
d_genocide(sb->s_root);
kill_anon_super(sb);
}
EXPORT_SYMBOL(kill_litter_super);
int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
{
return set_anon_super(sb, NULL);
}
EXPORT_SYMBOL(set_anon_super_fc);
static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
{
return sb->s_fs_info == fc->s_fs_info;
}
static int test_single_super(struct super_block *s, struct fs_context *fc)
{
return 1;
}
static int vfs_get_super(struct fs_context *fc,
int (*test)(struct super_block *, struct fs_context *),
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
{
struct super_block *sb;
int err;
sb = sget_fc(fc, test, set_anon_super_fc);
if (IS_ERR(sb))
return PTR_ERR(sb);
if (!sb->s_root) {
err = fill_super(sb, fc);
if (err)
goto error;
sb->s_flags |= SB_ACTIVE;
}
fc->root = dget(sb->s_root);
return 0;
error:
deactivate_locked_super(sb);
return err;
}
int get_tree_nodev(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
{
return vfs_get_super(fc, NULL, fill_super);
}
EXPORT_SYMBOL(get_tree_nodev);
int get_tree_single(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
{
return vfs_get_super(fc, test_single_super, fill_super);
}
EXPORT_SYMBOL(get_tree_single);
int get_tree_keyed(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc),
void *key)
{
fc->s_fs_info = key;
return vfs_get_super(fc, test_keyed_super, fill_super);
}
EXPORT_SYMBOL(get_tree_keyed);
static int set_bdev_super(struct super_block *s, void *data)
{
s->s_dev = *(dev_t *)data;
return 0;
}
static int super_s_dev_set(struct super_block *s, struct fs_context *fc)
{
return set_bdev_super(s, fc->sget_key);
}
static int super_s_dev_test(struct super_block *s, struct fs_context *fc)
{
return !(s->s_iflags & SB_I_RETIRED) &&
s->s_dev == *(dev_t *)fc->sget_key;
}
/**
* sget_dev - Find or create a superblock by device number
* @fc: Filesystem context.
* @dev: device number
*
* Find or create a superblock using the provided device number that
* will be stored in fc->sget_key.
*
* If an extant superblock is matched, then that will be returned with
* an elevated reference count that the caller must transfer or discard.
*
* If no match is made, a new superblock will be allocated and basic
* initialisation will be performed (s_type, s_fs_info, s_id, s_dev will
* be set). The superblock will be published and it will be returned in
* a partially constructed state with SB_BORN and SB_ACTIVE as yet
* unset.
*
* Return: an existing or newly created superblock on success, an error
* pointer on failure.
*/
struct super_block *sget_dev(struct fs_context *fc, dev_t dev)
{
fc->sget_key = &dev;
return sget_fc(fc, super_s_dev_test, super_s_dev_set);
}
EXPORT_SYMBOL(sget_dev);
#ifdef CONFIG_BLOCK
/*
* Lock the superblock that is holder of the bdev. Returns the superblock
* pointer if we successfully locked the superblock and it is alive. Otherwise
* we return NULL and just unlock bdev->bd_holder_lock.
*
* The function must be called with bdev->bd_holder_lock and releases it.
*/
static struct super_block *bdev_super_lock(struct block_device *bdev, bool excl)
__releases(&bdev->bd_holder_lock)
{
struct super_block *sb = bdev->bd_holder;
bool locked;
lockdep_assert_held(&bdev->bd_holder_lock);
lockdep_assert_not_held(&sb->s_umount);
lockdep_assert_not_held(&bdev->bd_disk->open_mutex);
/* Make sure sb doesn't go away from under us */
spin_lock(&sb_lock);
sb->s_count++;
spin_unlock(&sb_lock);
mutex_unlock(&bdev->bd_holder_lock);
locked = super_lock(sb, excl);
/*
* If the superblock wasn't already SB_DYING then we hold
* s_umount and can safely drop our temporary reference.
*/
put_super(sb);
if (!locked)
return NULL;
if (!sb->s_root || !(sb->s_flags & SB_ACTIVE)) {
super_unlock(sb, excl);
return NULL;
}
return sb;
}
static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
{
struct super_block *sb;
sb = bdev_super_lock(bdev, false);
if (!sb)
return;
if (!surprise)
sync_filesystem(sb);
shrink_dcache_sb(sb);
invalidate_inodes(sb);
if (sb->s_op->shutdown)
sb->s_op->shutdown(sb);
super_unlock_shared(sb);
}
static void fs_bdev_sync(struct block_device *bdev)
{
struct super_block *sb;
sb = bdev_super_lock(bdev, false);
if (!sb)
return;
sync_filesystem(sb);
super_unlock_shared(sb);
}
static struct super_block *get_bdev_super(struct block_device *bdev)
{
bool active = false;
struct super_block *sb;
sb = bdev_super_lock(bdev, true);
if (sb) {
active = atomic_inc_not_zero(&sb->s_active);
super_unlock_excl(sb);
}
if (!active)
return NULL;
return sb;
}
/**
* fs_bdev_freeze - freeze owning filesystem of block device
* @bdev: block device
*
* Freeze the filesystem that owns this block device if it is still
* active.
*
* A filesystem that owns multiple block devices may be frozen from each
* block device and won't be unfrozen until all block devices are
* unfrozen. Each block device can only freeze the filesystem once as we
* nest freezes for block devices in the block layer.
*
* Return: If the freeze was successful zero is returned. If the freeze
* failed a negative error code is returned.
*/
static int fs_bdev_freeze(struct block_device *bdev)
{
struct super_block *sb;
int error = 0;
lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
sb = get_bdev_super(bdev);
if (!sb)
return -EINVAL;
if (sb->s_op->freeze_super)
error = sb->s_op->freeze_super(sb,
FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
else
error = freeze_super(sb,
FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
if (!error)
error = sync_blockdev(bdev);
deactivate_super(sb);
return error;
}
/**
* fs_bdev_thaw - thaw owning filesystem of block device
* @bdev: block device
*
* Thaw the filesystem that owns this block device.
*
* A filesystem that owns multiple block devices may be frozen from each
* block device and won't be unfrozen until all block devices are
* unfrozen. Each block device can only freeze the filesystem once as we
* nest freezes for block devices in the block layer.
*
* Return: If the thaw was successful zero is returned. If the thaw
* failed a negative error code is returned. If this function
* returns zero it doesn't mean that the filesystem is unfrozen
* as it may have been frozen multiple times (kernel may hold a
* freeze or might be frozen from other block devices).
*/
static int fs_bdev_thaw(struct block_device *bdev)
{
struct super_block *sb;
int error;
lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
/*
* The block device may have been frozen before it was claimed by a
* filesystem. Concurrently another process might try to mount that
* frozen block device and has temporarily claimed the block device for
* that purpose causing a concurrent fs_bdev_thaw() to end up here. The
* mounter is already about to abort mounting because they still saw an
* elevanted bdev->bd_fsfreeze_count so get_bdev_super() will return
* NULL in that case.
*/
sb = get_bdev_super(bdev);
if (!sb)
return -EINVAL;
if (sb->s_op->thaw_super)
error = sb->s_op->thaw_super(sb,
FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
else
error = thaw_super(sb,
FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
deactivate_super(sb);
return error;
}
const struct blk_holder_ops fs_holder_ops = {
.mark_dead = fs_bdev_mark_dead,
.sync = fs_bdev_sync,
.freeze = fs_bdev_freeze,
.thaw = fs_bdev_thaw,
};
EXPORT_SYMBOL_GPL(fs_holder_ops);
int setup_bdev_super(struct super_block *sb, int sb_flags,
struct fs_context *fc)
{
blk_mode_t mode = sb_open_mode(sb_flags);
struct file *bdev_file;
struct block_device *bdev;
bdev_file = bdev_file_open_by_dev(sb->s_dev, mode, sb, &fs_holder_ops);
if (IS_ERR(bdev_file)) {
if (fc)
errorf(fc, "%s: Can't open blockdev", fc->source);
return PTR_ERR(bdev_file);
}
bdev = file_bdev(bdev_file);
/*
* This really should be in blkdev_get_by_dev, but right now can't due
* to legacy issues that require us to allow opening a block device node
* writable from userspace even for a read-only block device.
*/
if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
bdev_fput(bdev_file);
return -EACCES;
}
/*
* It is enough to check bdev was not frozen before we set
* s_bdev as freezing will wait until SB_BORN is set.
*/
if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {
if (fc)
warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
bdev_fput(bdev_file);
return -EBUSY;
}
spin_lock(&sb_lock);
sb->s_bdev_file = bdev_file;
sb->s_bdev = bdev;
sb->s_bdi = bdi_get(bdev->bd_disk->bdi);
if (bdev_stable_writes(bdev))
sb->s_iflags |= SB_I_STABLE_WRITES;
spin_unlock(&sb_lock);
snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
shrinker_debugfs_rename(sb->s_shrink, "sb-%s:%s", sb->s_type->name,
sb->s_id);
sb_set_blocksize(sb, block_size(bdev));
return 0;
}
EXPORT_SYMBOL_GPL(setup_bdev_super);
/**
* get_tree_bdev - Get a superblock based on a single block device
* @fc: The filesystem context holding the parameters
* @fill_super: Helper to initialise a new superblock
*/
int get_tree_bdev(struct fs_context *fc,
int (*fill_super)(struct super_block *,
struct fs_context *))
{
struct super_block *s;
int error = 0;
dev_t dev;
if (!fc->source)
return invalf(fc, "No source specified");
error = lookup_bdev(fc->source, &dev);
if (error) {
errorf(fc, "%s: Can't lookup blockdev", fc->source);
return error;
}
fc->sb_flags |= SB_NOSEC;
s = sget_dev(fc, dev);
if (IS_ERR(s))
return PTR_ERR(s);
if (s->s_root) {
/* Don't summarily change the RO/RW state. */
if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
warnf(fc, "%pg: Can't mount, would change RO state", s->s_bdev);
deactivate_locked_super(s);
return -EBUSY;
}
} else {
error = setup_bdev_super(s, fc->sb_flags, fc);
if (!error)
error = fill_super(s, fc);
if (error) {
deactivate_locked_super(s);
return error;
}
s->s_flags |= SB_ACTIVE;
}
BUG_ON(fc->root);
fc->root = dget(s->s_root);
return 0;
}
EXPORT_SYMBOL(get_tree_bdev);
static int test_bdev_super(struct super_block *s, void *data)
{
return !(s->s_iflags & SB_I_RETIRED) && s->s_dev == *(dev_t *)data;
}
struct dentry *mount_bdev(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *s;
int error;
dev_t dev;
error = lookup_bdev(dev_name, &dev);
if (error)
return ERR_PTR(error);
flags |= SB_NOSEC;
s = sget(fs_type, test_bdev_super, set_bdev_super, flags, &dev);
if (IS_ERR(s))
return ERR_CAST(s);
if (s->s_root) {
if ((flags ^ s->s_flags) & SB_RDONLY) {
deactivate_locked_super(s);
return ERR_PTR(-EBUSY);
}
} else {
error = setup_bdev_super(s, flags, NULL);
if (!error)
error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
return ERR_PTR(error);
}
s->s_flags |= SB_ACTIVE;
}
return dget(s->s_root);
}
EXPORT_SYMBOL(mount_bdev);
void kill_block_super(struct super_block *sb)
{
struct block_device *bdev = sb->s_bdev;
generic_shutdown_super(sb);
if (bdev) {
sync_blockdev(bdev);
bdev_fput(sb->s_bdev_file);
}
}
EXPORT_SYMBOL(kill_block_super);
#endif
struct dentry *mount_nodev(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
int error;
struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
return ERR_PTR(error);
}
s->s_flags |= SB_ACTIVE;
return dget(s->s_root);
}
EXPORT_SYMBOL(mount_nodev);
int reconfigure_single(struct super_block *s,
int flags, void *data)
{
struct fs_context *fc;
int ret;
/* The caller really need to be passing fc down into mount_single(),
* then a chunk of this can be removed. [Bollocks -- AV]
* Better yet, reconfiguration shouldn't happen, but rather the second
* mount should be rejected if the parameters are not compatible.
*/
fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
if (IS_ERR(fc))
return PTR_ERR(fc);
ret = parse_monolithic_mount_data(fc, data);
if (ret < 0)
goto out;
ret = reconfigure_super(fc);
out:
put_fs_context(fc);
return ret;
}
static int compare_single(struct super_block *s, void *p)
{
return 1;
}
struct dentry *mount_single(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *s;
int error;
s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
if (!s->s_root) {
error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
if (!error)
s->s_flags |= SB_ACTIVE;
} else {
error = reconfigure_single(s, flags, data);
}
if (unlikely(error)) {
deactivate_locked_super(s);
return ERR_PTR(error);
}
return dget(s->s_root);
}
EXPORT_SYMBOL(mount_single);
/**
* vfs_get_tree - Get the mountable root
* @fc: The superblock configuration context.
*
* The filesystem is invoked to get or create a superblock which can then later
* be used for mounting. The filesystem places a pointer to the root to be
* used for mounting in @fc->root.
*/
int vfs_get_tree(struct fs_context *fc)
{
struct super_block *sb;
int error;
if (fc->root)
return -EBUSY;
/* Get the mountable root in fc->root, with a ref on the root and a ref
* on the superblock.
*/
error = fc->ops->get_tree(fc);
if (error < 0)
return error;
if (!fc->root) {
pr_err("Filesystem %s get_tree() didn't set fc->root\n",
fc->fs_type->name);
/* We don't know what the locking state of the superblock is -
* if there is a superblock.
*/
BUG();
}
sb = fc->root->d_sb;
WARN_ON(!sb->s_bdi);
/*
* super_wake() contains a memory barrier which also care of
* ordering for super_cache_count(). We place it before setting
* SB_BORN as the data dependency between the two functions is
* the superblock structure contents that we just set up, not
* the SB_BORN flag.
*/
super_wake(sb, SB_BORN);
error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
if (unlikely(error)) {
fc_drop_locked(fc);
return error;
}
/*
* filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
* but s_maxbytes was an unsigned long long for many releases. Throw
* this warning for a little while to try and catch filesystems that
* violate this rule.
*/
WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
"negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
return 0;
}
EXPORT_SYMBOL(vfs_get_tree);
/*
* Setup private BDI for given superblock. It gets automatically cleaned up
* in generic_shutdown_super().
*/
int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
{
struct backing_dev_info *bdi;
int err;
va_list args;
bdi = bdi_alloc(NUMA_NO_NODE);
if (!bdi)
return -ENOMEM;
va_start(args, fmt);
err = bdi_register_va(bdi, fmt, args);
va_end(args);
if (err) {
bdi_put(bdi);
return err;
}
WARN_ON(sb->s_bdi != &noop_backing_dev_info);
sb->s_bdi = bdi;
sb->s_iflags |= SB_I_PERSB_BDI;
return 0;
}
EXPORT_SYMBOL(super_setup_bdi_name);
/*
* Setup private BDI for given superblock. I gets automatically cleaned up
* in generic_shutdown_super().
*/
int super_setup_bdi(struct super_block *sb)
{
static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
atomic_long_inc_return(&bdi_seq));
}
EXPORT_SYMBOL(super_setup_bdi);
/**
* sb_wait_write - wait until all writers to given file system finish
* @sb: the super for which we wait
* @level: type of writers we wait for (normal vs page fault)
*
* This function waits until there are no writers of given type to given file
* system.
*/
static void sb_wait_write(struct super_block *sb, int level)
{
percpu_down_write(sb->s_writers.rw_sem + level-1);
}
/*
* We are going to return to userspace and forget about these locks, the
* ownership goes to the caller of thaw_super() which does unlock().
*/
static void lockdep_sb_freeze_release(struct super_block *sb)
{
int level;
for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
}
/*
* Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
*/
static void lockdep_sb_freeze_acquire(struct super_block *sb)
{
int level;
for (level = 0; level < SB_FREEZE_LEVELS; ++level)
percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
}
static void sb_freeze_unlock(struct super_block *sb, int level)
{
for (level--; level >= 0; level--)
percpu_up_write(sb->s_writers.rw_sem + level);
}
static int wait_for_partially_frozen(struct super_block *sb)
{
int ret = 0;
do {
unsigned short old = sb->s_writers.frozen;
up_write(&sb->s_umount);
ret = wait_var_event_killable(&sb->s_writers.frozen,
sb->s_writers.frozen != old);
down_write(&sb->s_umount);
} while (ret == 0 &&
sb->s_writers.frozen != SB_UNFROZEN &&
sb->s_writers.frozen != SB_FREEZE_COMPLETE);
return ret;
}
#define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE)
#define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST)
static inline int freeze_inc(struct super_block *sb, enum freeze_holder who)
{
WARN_ON_ONCE((who & ~FREEZE_FLAGS));
WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
if (who & FREEZE_HOLDER_KERNEL)
++sb->s_writers.freeze_kcount;
if (who & FREEZE_HOLDER_USERSPACE)
++sb->s_writers.freeze_ucount;
return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
}
static inline int freeze_dec(struct super_block *sb, enum freeze_holder who)
{
WARN_ON_ONCE((who & ~FREEZE_FLAGS));
WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
if ((who & FREEZE_HOLDER_KERNEL) && sb->s_writers.freeze_kcount)
--sb->s_writers.freeze_kcount;
if ((who & FREEZE_HOLDER_USERSPACE) && sb->s_writers.freeze_ucount)
--sb->s_writers.freeze_ucount;
return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
}
static inline bool may_freeze(struct super_block *sb, enum freeze_holder who)
{
WARN_ON_ONCE((who & ~FREEZE_FLAGS));
WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
if (who & FREEZE_HOLDER_KERNEL)
return (who & FREEZE_MAY_NEST) ||
sb->s_writers.freeze_kcount == 0;
if (who & FREEZE_HOLDER_USERSPACE)
return (who & FREEZE_MAY_NEST) ||
sb->s_writers.freeze_ucount == 0;
return false;
}
/**
* freeze_super - lock the filesystem and force it into a consistent state
* @sb: the super to lock
* @who: context that wants to freeze
*
* Syncs the super to make sure the filesystem is consistent and calls the fs's
* freeze_fs. Subsequent calls to this without first thawing the fs may return
* -EBUSY.
*
* @who should be:
* * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;
* * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.
* * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed.
*
* The @who argument distinguishes between the kernel and userspace trying to
* freeze the filesystem. Although there cannot be multiple kernel freezes or
* multiple userspace freezes in effect at any given time, the kernel and
* userspace can both hold a filesystem frozen. The filesystem remains frozen
* until there are no kernel or userspace freezes in effect.
*
* A filesystem may hold multiple devices and thus a filesystems may be
* frozen through the block layer via multiple block devices. In this
* case the request is marked as being allowed to nest by passing
* FREEZE_MAY_NEST. The filesystem remains frozen until all block
* devices are unfrozen. If multiple freezes are attempted without
* FREEZE_MAY_NEST -EBUSY will be returned.
*
* During this function, sb->s_writers.frozen goes through these values:
*
* SB_UNFROZEN: File system is normal, all writes progress as usual.
*
* SB_FREEZE_WRITE: The file system is in the process of being frozen. New
* writes should be blocked, though page faults are still allowed. We wait for
* all writes to complete and then proceed to the next stage.
*
* SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
* but internal fs threads can still modify the filesystem (although they
* should not dirty new pages or inodes), writeback can run etc. After waiting
* for all running page faults we sync the filesystem which will clean all
* dirty pages and inodes (no new dirty pages or inodes can be created when
* sync is running).
*
* SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
* modification are blocked (e.g. XFS preallocation truncation on inode
* reclaim). This is usually implemented by blocking new transactions for
* filesystems that have them and need this additional guard. After all
* internal writers are finished we call ->freeze_fs() to finish filesystem
* freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
* mostly auxiliary for filesystems to verify they do not modify frozen fs.
*
* sb->s_writers.frozen is protected by sb->s_umount.
*
* Return: If the freeze was successful zero is returned. If the freeze
* failed a negative error code is returned.
*/
int freeze_super(struct super_block *sb, enum freeze_holder who)
{
int ret;
if (!super_lock_excl(sb)) {
WARN_ON_ONCE("Dying superblock while freezing!");
return -EINVAL;
}
atomic_inc(&sb->s_active);
retry:
if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) {
if (may_freeze(sb, who))
ret = !!WARN_ON_ONCE(freeze_inc(sb, who) == 1);
else
ret = -EBUSY;
/* All freezers share a single active reference. */
deactivate_locked_super(sb);
return ret;
}
if (sb->s_writers.frozen != SB_UNFROZEN) {
ret = wait_for_partially_frozen(sb);
if (ret) {
deactivate_locked_super(sb);
return ret;
}
goto retry;
}
if (sb_rdonly(sb)) {
/* Nothing to do really... */
WARN_ON_ONCE(freeze_inc(sb, who) > 1);
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
wake_up_var(&sb->s_writers.frozen);
super_unlock_excl(sb);
return 0;
}
sb->s_writers.frozen = SB_FREEZE_WRITE;
/* Release s_umount to preserve sb_start_write -> s_umount ordering */
super_unlock_excl(sb);
sb_wait_write(sb, SB_FREEZE_WRITE);
__super_lock_excl(sb);
/* Now we go and block page faults... */
sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
/* All writers are done so after syncing there won't be dirty data */
ret = sync_filesystem(sb);
if (ret) {
sb->s_writers.frozen = SB_UNFROZEN;
sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
wake_up_var(&sb->s_writers.frozen);
deactivate_locked_super(sb);
return ret;
}
/* Now wait for internal filesystem counter */
sb->s_writers.frozen = SB_FREEZE_FS;
sb_wait_write(sb, SB_FREEZE_FS);
if (sb->s_op->freeze_fs) {
ret = sb->s_op->freeze_fs(sb);
if (ret) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
sb->s_writers.frozen = SB_UNFROZEN;
sb_freeze_unlock(sb, SB_FREEZE_FS);
wake_up_var(&sb->s_writers.frozen);
deactivate_locked_super(sb);
return ret;
}
}
/*
* For debugging purposes so that fs can warn if it sees write activity
* when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
*/
WARN_ON_ONCE(freeze_inc(sb, who) > 1);
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
wake_up_var(&sb->s_writers.frozen);
lockdep_sb_freeze_release(sb);
super_unlock_excl(sb);
return 0;
}
EXPORT_SYMBOL(freeze_super);
/*
* Undoes the effect of a freeze_super_locked call. If the filesystem is
* frozen both by userspace and the kernel, a thaw call from either source
* removes that state without releasing the other state or unlocking the
* filesystem.
*/
static int thaw_super_locked(struct super_block *sb, enum freeze_holder who)
{
int error = -EINVAL;
if (sb->s_writers.frozen != SB_FREEZE_COMPLETE)
goto out_unlock;
/*
* All freezers share a single active reference.
* So just unlock in case there are any left.
*/
if (freeze_dec(sb, who))
goto out_unlock;
if (sb_rdonly(sb)) {
sb->s_writers.frozen = SB_UNFROZEN;
wake_up_var(&sb->s_writers.frozen);
goto out_deactivate;
}
lockdep_sb_freeze_acquire(sb);
if (sb->s_op->unfreeze_fs) {
error = sb->s_op->unfreeze_fs(sb);
if (error) {
pr_err("VFS: Filesystem thaw failed\n");
freeze_inc(sb, who);
lockdep_sb_freeze_release(sb);
goto out_unlock;
}
}
sb->s_writers.frozen = SB_UNFROZEN;
wake_up_var(&sb->s_writers.frozen);
sb_freeze_unlock(sb, SB_FREEZE_FS);
out_deactivate:
deactivate_locked_super(sb);
return 0;
out_unlock:
super_unlock_excl(sb);
return error;
}
/**
* thaw_super -- unlock filesystem
* @sb: the super to thaw
* @who: context that wants to freeze
*
* Unlocks the filesystem and marks it writeable again after freeze_super()
* if there are no remaining freezes on the filesystem.
*
* @who should be:
* * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;
* * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.
* * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed
*
* A filesystem may hold multiple devices and thus a filesystems may
* have been frozen through the block layer via multiple block devices.
* The filesystem remains frozen until all block devices are unfrozen.
*/
int thaw_super(struct super_block *sb, enum freeze_holder who)
{
if (!super_lock_excl(sb)) {
WARN_ON_ONCE("Dying superblock while thawing!");
return -EINVAL;
}
return thaw_super_locked(sb, who);
}
EXPORT_SYMBOL(thaw_super);
/*
* Create workqueue for deferred direct IO completions. We allocate the
* workqueue when it's first needed. This avoids creating workqueue for
* filesystems that don't need it and also allows us to create the workqueue
* late enough so the we can include s_id in the name of the workqueue.
*/
int sb_init_dio_done_wq(struct super_block *sb)
{
struct workqueue_struct *old;
struct workqueue_struct *wq = alloc_workqueue("dio/%s",
WQ_MEM_RECLAIM, 0,
sb->s_id);
if (!wq)
return -ENOMEM;
/*
* This has to be atomic as more DIOs can race to create the workqueue
*/
old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
/* Someone created workqueue before us? Free ours... */
if (old)
destroy_workqueue(wq);
return 0;
}
EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);