// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
 *  Copyright (C) 2016 - 2020 Christoph Hellwig
 */

#include <linux/init.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/device_cgroup.h>
#include <linux/blkdev.h>
#include <linux/blk-integrity.h>
#include <linux/backing-dev.h>
#include <linux/module.h>
#include <linux/blkpg.h>
#include <linux/magic.h>
#include <linux/buffer_head.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/uio.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/part_stat.h>
#include <linux/uaccess.h>
#include <linux/stat.h>
#include "../fs/internal.h"
#include "blk.h"

/* Should we allow writing to mounted block devices? */
static bool bdev_allow_write_mounted = IS_ENABLED(CONFIG_BLK_DEV_WRITE_MOUNTED);

struct bdev_inode {
        struct block_device bdev;
        struct inode vfs_inode;
};

static inline struct bdev_inode *BDEV_I(struct inode *inode)
{
        return container_of(inode, struct bdev_inode, vfs_inode);
}

static inline struct inode *BD_INODE(struct block_device *bdev)
{
        return &container_of(bdev, struct bdev_inode, bdev)->vfs_inode;
}

struct block_device *I_BDEV(struct inode *inode)
{
        return &BDEV_I(inode)->bdev;
}
EXPORT_SYMBOL(I_BDEV);

struct block_device *file_bdev(struct file *bdev_file)
{
        return I_BDEV(bdev_file->f_mapping->host);
}
EXPORT_SYMBOL(file_bdev);

static void bdev_write_inode(struct block_device *bdev)
{
        struct inode *inode = BD_INODE(bdev);
        int ret;

        spin_lock(&inode->i_lock);
        while (inode_state_read(inode) & I_DIRTY) {
                spin_unlock(&inode->i_lock);
                ret = write_inode_now(inode, true);
                if (ret)
                        pr_warn_ratelimited(
        "VFS: Dirty inode writeback failed for block device %pg (err=%d).\n",
                                bdev, ret);
                spin_lock(&inode->i_lock);
        }
        spin_unlock(&inode->i_lock);
}

/* Kill _all_ buffers and pagecache , dirty or not.. */
static void kill_bdev(struct block_device *bdev)
{
        struct address_space *mapping = bdev->bd_mapping;

        if (mapping_empty(mapping))
                return;

        invalidate_bh_lrus();
        truncate_inode_pages(mapping, 0);
}

/* Invalidate clean unused buffers and pagecache. */
void invalidate_bdev(struct block_device *bdev)
{
        struct address_space *mapping = bdev->bd_mapping;

        if (mapping->nrpages) {
                invalidate_bh_lrus();
                lru_add_drain_all();    /* make sure all lru add caches are flushed */
                invalidate_mapping_pages(mapping, 0, -1);
        }
}
EXPORT_SYMBOL(invalidate_bdev);

/*
 * Drop all buffers & page cache for given bdev range. This function bails
 * with error if bdev has other exclusive owner (such as filesystem).
 */
int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode,
                        loff_t lstart, loff_t lend)
{
        /*
         * If we don't hold exclusive handle for the device, upgrade to it
         * while we discard the buffer cache to avoid discarding buffers
         * under live filesystem.
         */
        if (!(mode & BLK_OPEN_EXCL)) {
                int err = bd_prepare_to_claim(bdev, truncate_bdev_range, NULL);
                if (err)
                        goto invalidate;
        }

        truncate_inode_pages_range(bdev->bd_mapping, lstart, lend);
        if (!(mode & BLK_OPEN_EXCL))
                bd_abort_claiming(bdev, truncate_bdev_range);
        return 0;

invalidate:
        /*
         * Someone else has handle exclusively open. Try invalidating instead.
         * The 'end' argument is inclusive so the rounding is safe.
         */
        return invalidate_inode_pages2_range(bdev->bd_mapping,
                                             lstart >> PAGE_SHIFT,
                                             lend >> PAGE_SHIFT);
}

static void set_init_blocksize(struct block_device *bdev)
{
        unsigned int bsize = bdev_logical_block_size(bdev);
        loff_t size = i_size_read(BD_INODE(bdev));

        while (bsize < PAGE_SIZE) {
                if (size & bsize)
                        break;
                bsize <<= 1;
        }
        BD_INODE(bdev)->i_blkbits = blksize_bits(bsize);
        mapping_set_folio_min_order(BD_INODE(bdev)->i_mapping,
                                    get_order(bsize));
}

/**
 * bdev_validate_blocksize - check that this block size is acceptable
 * @bdev:       blockdevice to check
 * @block_size: block size to check
 *
 * For block device users that do not use buffer heads or the block device
 * page cache, make sure that this block size can be used with the device.
 *
 * Return: On success zero is returned, negative error code on failure.
 */
int bdev_validate_blocksize(struct block_device *bdev, int block_size)
{
        if (blk_validate_block_size(block_size))
                return -EINVAL;

        /* Size cannot be smaller than the size supported by the device */
        if (block_size < bdev_logical_block_size(bdev))
                return -EINVAL;

        return 0;
}
EXPORT_SYMBOL_GPL(bdev_validate_blocksize);

int set_blocksize(struct file *file, int size)
{
        struct inode *inode = file->f_mapping->host;
        struct block_device *bdev = I_BDEV(inode);
        int ret;

        ret = bdev_validate_blocksize(bdev, size);
        if (ret)
                return ret;

        if (!file->private_data)
                return -EINVAL;

        /* Don't change the size if it is same as current */
        if (inode->i_blkbits != blksize_bits(size)) {
                /*
                 * Flush and truncate the pagecache before we reconfigure the
                 * mapping geometry because folio sizes are variable now.  If a
                 * reader has already allocated a folio whose size is smaller
                 * than the new min_order but invokes readahead after the new
                 * min_order becomes visible, readahead will think there are
                 * "zero" blocks per folio and crash.  Take the inode and
                 * invalidation locks to avoid racing with
                 * read/write/fallocate.
                 */
                inode_lock(inode);
                filemap_invalidate_lock(inode->i_mapping);

                sync_blockdev(bdev);
                kill_bdev(bdev);

                inode->i_blkbits = blksize_bits(size);
                mapping_set_folio_min_order(inode->i_mapping, get_order(size));
                filemap_invalidate_unlock(inode->i_mapping);
                inode_unlock(inode);
        }
        return 0;
}

EXPORT_SYMBOL(set_blocksize);

static int sb_validate_large_blocksize(struct super_block *sb, int size)
{
        const char *err_str = NULL;

        if (!(sb->s_type->fs_flags & FS_LBS))
                err_str = "not supported by filesystem";
        else if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
                err_str = "is only supported with CONFIG_TRANSPARENT_HUGEPAGE";

        if (!err_str)
                return 0;

        pr_warn_ratelimited("%s: block size(%d) > page size(%lu) %s\n",
                                sb->s_type->name, size, PAGE_SIZE, err_str);
        return -EINVAL;
}

int sb_set_blocksize(struct super_block *sb, int size)
{
        if (size > PAGE_SIZE && sb_validate_large_blocksize(sb, size))
                return 0;
        if (set_blocksize(sb->s_bdev_file, size))
                return 0;
        /* If we get here, we know size is validated */
        sb->s_blocksize = size;
        sb->s_blocksize_bits = blksize_bits(size);
        return sb->s_blocksize;
}

EXPORT_SYMBOL(sb_set_blocksize);

int __must_check sb_min_blocksize(struct super_block *sb, int size)
{
        int minsize = bdev_logical_block_size(sb->s_bdev);
        if (size < minsize)
                size = minsize;
        return sb_set_blocksize(sb, size);
}

EXPORT_SYMBOL(sb_min_blocksize);

int sync_blockdev_nowait(struct block_device *bdev)
{
        if (!bdev)
                return 0;
        return filemap_flush(bdev->bd_mapping);
}
EXPORT_SYMBOL_GPL(sync_blockdev_nowait);

/*
 * Write out and wait upon all the dirty data associated with a block
 * device via its mapping.  Does not take the superblock lock.
 */
int sync_blockdev(struct block_device *bdev)
{
        if (!bdev)
                return 0;
        return filemap_write_and_wait(bdev->bd_mapping);
}
EXPORT_SYMBOL(sync_blockdev);

int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend)
{
        return filemap_write_and_wait_range(bdev->bd_mapping,
                        lstart, lend);
}
EXPORT_SYMBOL(sync_blockdev_range);

/**
 * bdev_freeze - lock a filesystem and force it into a consistent state
 * @bdev:       blockdevice to lock
 *
 * If a superblock is found on this device, we take the s_umount semaphore
 * on it to make sure nobody unmounts until the snapshot creation is done.
 * The reference counter (bd_fsfreeze_count) guarantees that only the last
 * unfreeze process can unfreeze the frozen filesystem actually when multiple
 * freeze requests arrive simultaneously. It counts up in bdev_freeze() and
 * count down in bdev_thaw(). When it becomes 0, thaw_bdev() will unfreeze
 * actually.
 *
 * Return: On success zero is returned, negative error code on failure.
 */
int bdev_freeze(struct block_device *bdev)
{
        int error = 0;

        mutex_lock(&bdev->bd_fsfreeze_mutex);

        if (atomic_inc_return(&bdev->bd_fsfreeze_count) > 1) {
                mutex_unlock(&bdev->bd_fsfreeze_mutex);
                return 0;
        }

        mutex_lock(&bdev->bd_holder_lock);
        if (bdev->bd_holder_ops && bdev->bd_holder_ops->freeze) {
                error = bdev->bd_holder_ops->freeze(bdev);
                lockdep_assert_not_held(&bdev->bd_holder_lock);
        } else {
                mutex_unlock(&bdev->bd_holder_lock);
                error = sync_blockdev(bdev);
        }

        if (error)
                atomic_dec(&bdev->bd_fsfreeze_count);

        mutex_unlock(&bdev->bd_fsfreeze_mutex);
        return error;
}
EXPORT_SYMBOL(bdev_freeze);

/**
 * bdev_thaw - unlock filesystem
 * @bdev:       blockdevice to unlock
 *
 * Unlocks the filesystem and marks it writeable again after bdev_freeze().
 *
 * Return: On success zero is returned, negative error code on failure.
 */
int bdev_thaw(struct block_device *bdev)
{
        int error = -EINVAL, nr_freeze;

        mutex_lock(&bdev->bd_fsfreeze_mutex);

        /*
         * If this returns < 0 it means that @bd_fsfreeze_count was
         * already 0 and no decrement was performed.
         */
        nr_freeze = atomic_dec_if_positive(&bdev->bd_fsfreeze_count);
        if (nr_freeze < 0)
                goto out;

        error = 0;
        if (nr_freeze > 0)
                goto out;

        mutex_lock(&bdev->bd_holder_lock);
        if (bdev->bd_holder_ops && bdev->bd_holder_ops->thaw) {
                error = bdev->bd_holder_ops->thaw(bdev);
                lockdep_assert_not_held(&bdev->bd_holder_lock);
        } else {
                mutex_unlock(&bdev->bd_holder_lock);
        }

        if (error)
                atomic_inc(&bdev->bd_fsfreeze_count);
out:
        mutex_unlock(&bdev->bd_fsfreeze_mutex);
        return error;
}
EXPORT_SYMBOL(bdev_thaw);

/*
 * pseudo-fs
 */

static  __cacheline_aligned_in_smp DEFINE_MUTEX(bdev_lock);
static struct kmem_cache *bdev_cachep __ro_after_init;

static struct inode *bdev_alloc_inode(struct super_block *sb)
{
        struct bdev_inode *ei = alloc_inode_sb(sb, bdev_cachep, GFP_KERNEL);

        if (!ei)
                return NULL;
        memset(&ei->bdev, 0, sizeof(ei->bdev));

        if (security_bdev_alloc(&ei->bdev)) {
                kmem_cache_free(bdev_cachep, ei);
                return NULL;
        }
        return &ei->vfs_inode;
}

static void bdev_free_inode(struct inode *inode)
{
        struct block_device *bdev = I_BDEV(inode);

        free_percpu(bdev->bd_stats);
        kfree(bdev->bd_meta_info);
        security_bdev_free(bdev);

        if (!bdev_is_partition(bdev)) {
                if (bdev->bd_disk && bdev->bd_disk->bdi)
                        bdi_put(bdev->bd_disk->bdi);
                kfree(bdev->bd_disk);
        }

        if (MAJOR(bdev->bd_dev) == BLOCK_EXT_MAJOR)
                blk_free_ext_minor(MINOR(bdev->bd_dev));

        kmem_cache_free(bdev_cachep, BDEV_I(inode));
}

static void init_once(void *data)
{
        struct bdev_inode *ei = data;

        inode_init_once(&ei->vfs_inode);
}

static void bdev_evict_inode(struct inode *inode)
{
        truncate_inode_pages_final(&inode->i_data);
        invalidate_inode_buffers(inode); /* is it needed here? */
        clear_inode(inode);
}

static const struct super_operations bdev_sops = {
        .statfs = simple_statfs,
        .alloc_inode = bdev_alloc_inode,
        .free_inode = bdev_free_inode,
        .drop_inode = inode_just_drop,
        .evict_inode = bdev_evict_inode,
};

static int bd_init_fs_context(struct fs_context *fc)
{
        struct pseudo_fs_context *ctx = init_pseudo(fc, BDEVFS_MAGIC);
        if (!ctx)
                return -ENOMEM;
        fc->s_iflags |= SB_I_CGROUPWB;
        ctx->ops = &bdev_sops;
        return 0;
}

static struct file_system_type bd_type = {
        .name           = "bdev",
        .init_fs_context = bd_init_fs_context,
        .kill_sb        = kill_anon_super,
};

struct super_block *blockdev_superblock __ro_after_init;
static struct vfsmount *blockdev_mnt __ro_after_init;
EXPORT_SYMBOL_GPL(blockdev_superblock);

void __init bdev_cache_init(void)
{
        int err;

        bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
                        0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                                SLAB_ACCOUNT|SLAB_PANIC),
                        init_once);
        err = register_filesystem(&bd_type);
        if (err)
                panic("Cannot register bdev pseudo-fs");
        blockdev_mnt = kern_mount(&bd_type);
        if (IS_ERR(blockdev_mnt))
                panic("Cannot create bdev pseudo-fs");
        blockdev_superblock = blockdev_mnt->mnt_sb;   /* For writeback */
}

struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
{
        struct block_device *bdev;
        struct inode *inode;

        inode = new_inode(blockdev_superblock);
        if (!inode)
                return NULL;
        inode->i_mode = S_IFBLK;
        inode->i_rdev = 0;
        inode->i_data.a_ops = &def_blk_aops;
        mapping_set_gfp_mask(&inode->i_data, GFP_USER);

        bdev = I_BDEV(inode);
        mutex_init(&bdev->bd_fsfreeze_mutex);
        spin_lock_init(&bdev->bd_size_lock);
        mutex_init(&bdev->bd_holder_lock);
        atomic_set(&bdev->__bd_flags, partno);
        bdev->bd_mapping = &inode->i_data;
        bdev->bd_queue = disk->queue;
        if (partno && bdev_test_flag(disk->part0, BD_HAS_SUBMIT_BIO))
                bdev_set_flag(bdev, BD_HAS_SUBMIT_BIO);
        bdev->bd_stats = alloc_percpu(struct disk_stats);
        if (!bdev->bd_stats) {
                iput(inode);
                return NULL;
        }
        bdev->bd_disk = disk;
        return bdev;
}

void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
{
        spin_lock(&bdev->bd_size_lock);
        i_size_write(BD_INODE(bdev), (loff_t)sectors << SECTOR_SHIFT);
        bdev->bd_nr_sectors = sectors;
        spin_unlock(&bdev->bd_size_lock);
}

void bdev_add(struct block_device *bdev, dev_t dev)
{
        struct inode *inode = BD_INODE(bdev);
        if (bdev_stable_writes(bdev))
                mapping_set_stable_writes(bdev->bd_mapping);
        bdev->bd_dev = dev;
        inode->i_rdev = dev;
        inode->i_ino = dev;
        insert_inode_hash(inode);
}

void bdev_unhash(struct block_device *bdev)
{
        remove_inode_hash(BD_INODE(bdev));
}

void bdev_drop(struct block_device *bdev)
{
        iput(BD_INODE(bdev));
}

long nr_blockdev_pages(void)
{
        struct inode *inode;
        long ret = 0;

        spin_lock(&blockdev_superblock->s_inode_list_lock);
        list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
                ret += inode->i_mapping->nrpages;
        spin_unlock(&blockdev_superblock->s_inode_list_lock);

        return ret;
}

/**
 * bd_may_claim - test whether a block device can be claimed
 * @bdev: block device of interest
 * @holder: holder trying to claim @bdev
 * @hops: holder ops
 *
 * Test whether @bdev can be claimed by @holder.
 *
 * RETURNS:
 * %true if @bdev can be claimed, %false otherwise.
 */
static bool bd_may_claim(struct block_device *bdev, void *holder,
                const struct blk_holder_ops *hops)
{
        struct block_device *whole = bdev_whole(bdev);

        lockdep_assert_held(&bdev_lock);

        if (bdev->bd_holder) {
                /*
                 * The same holder can always re-claim.
                 */
                if (bdev->bd_holder == holder) {
                        if (WARN_ON_ONCE(bdev->bd_holder_ops != hops))
                                return false;
                        return true;
                }
                return false;
        }

        /*
         * If the whole devices holder is set to bd_may_claim, a partition on
         * the device is claimed, but not the whole device.
         */
        if (whole != bdev &&
            whole->bd_holder && whole->bd_holder != bd_may_claim)
                return false;
        return true;
}

/**
 * bd_prepare_to_claim - claim a block device
 * @bdev: block device of interest
 * @holder: holder trying to claim @bdev
 * @hops: holder ops.
 *
 * Claim @bdev.  This function fails if @bdev is already claimed by another
 * holder and waits if another claiming is in progress. return, the caller
 * has ownership of bd_claiming and bd_holder[s].
 *
 * RETURNS:
 * 0 if @bdev can be claimed, -EBUSY otherwise.
 */
int bd_prepare_to_claim(struct block_device *bdev, void *holder,
                const struct blk_holder_ops *hops)
{
        struct block_device *whole = bdev_whole(bdev);

        if (WARN_ON_ONCE(!holder))
                return -EINVAL;
retry:
        mutex_lock(&bdev_lock);
        /* if someone else claimed, fail */
        if (!bd_may_claim(bdev, holder, hops)) {
                mutex_unlock(&bdev_lock);
                return -EBUSY;
        }

        /* if claiming is already in progress, wait for it to finish */
        if (whole->bd_claiming) {
                wait_queue_head_t *wq = __var_waitqueue(&whole->bd_claiming);
                DEFINE_WAIT(wait);

                prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
                mutex_unlock(&bdev_lock);
                schedule();
                finish_wait(wq, &wait);
                goto retry;
        }

        /* yay, all mine */
        whole->bd_claiming = holder;
        mutex_unlock(&bdev_lock);
        return 0;
}
EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */

static void bd_clear_claiming(struct block_device *whole, void *holder)
{
        lockdep_assert_held(&bdev_lock);
        /* tell others that we're done */
        BUG_ON(whole->bd_claiming != holder);
        whole->bd_claiming = NULL;
        wake_up_var(&whole->bd_claiming);
}

/**
 * bd_finish_claiming - finish claiming of a block device
 * @bdev: block device of interest
 * @holder: holder that has claimed @bdev
 * @hops: block device holder operations
 *
 * Finish exclusive open of a block device. Mark the device as exlusively
 * open by the holder and wake up all waiters for exclusive open to finish.
 */
static void bd_finish_claiming(struct block_device *bdev, void *holder,
                const struct blk_holder_ops *hops)
{
        struct block_device *whole = bdev_whole(bdev);

        mutex_lock(&bdev_lock);
        BUG_ON(!bd_may_claim(bdev, holder, hops));
        /*
         * Note that for a whole device bd_holders will be incremented twice,
         * and bd_holder will be set to bd_may_claim before being set to holder
         */
        whole->bd_holders++;
        whole->bd_holder = bd_may_claim;
        bdev->bd_holders++;
        mutex_lock(&bdev->bd_holder_lock);
        bdev->bd_holder = holder;
        bdev->bd_holder_ops = hops;
        mutex_unlock(&bdev->bd_holder_lock);
        bd_clear_claiming(whole, holder);
        mutex_unlock(&bdev_lock);
}

/**
 * bd_abort_claiming - abort claiming of a block device
 * @bdev: block device of interest
 * @holder: holder that has claimed @bdev
 *
 * Abort claiming of a block device when the exclusive open failed. This can be
 * also used when exclusive open is not actually desired and we just needed
 * to block other exclusive openers for a while.
 */
void bd_abort_claiming(struct block_device *bdev, void *holder)
{
        mutex_lock(&bdev_lock);
        bd_clear_claiming(bdev_whole(bdev), holder);
        mutex_unlock(&bdev_lock);
}
EXPORT_SYMBOL(bd_abort_claiming);

static void bd_end_claim(struct block_device *bdev, void *holder)
{
        struct block_device *whole = bdev_whole(bdev);
        bool unblock = false;

        /*
         * Release a claim on the device.  The holder fields are protected with
         * bdev_lock.  open_mutex is used to synchronize disk_holder unlinking.
         */
        mutex_lock(&bdev_lock);
        WARN_ON_ONCE(bdev->bd_holder != holder);
        WARN_ON_ONCE(--bdev->bd_holders < 0);
        WARN_ON_ONCE(--whole->bd_holders < 0);
        if (!bdev->bd_holders) {
                mutex_lock(&bdev->bd_holder_lock);
                bdev->bd_holder = NULL;
                bdev->bd_holder_ops = NULL;
                mutex_unlock(&bdev->bd_holder_lock);
                if (bdev_test_flag(bdev, BD_WRITE_HOLDER))
                        unblock = true;
        }
        if (!whole->bd_holders)
                whole->bd_holder = NULL;
        mutex_unlock(&bdev_lock);

        /*
         * If this was the last claim, remove holder link and unblock evpoll if
         * it was a write holder.
         */
        if (unblock) {
                disk_unblock_events(bdev->bd_disk);
                bdev_clear_flag(bdev, BD_WRITE_HOLDER);
        }
}

static void blkdev_flush_mapping(struct block_device *bdev)
{
        WARN_ON_ONCE(bdev->bd_holders);
        sync_blockdev(bdev);
        kill_bdev(bdev);
        bdev_write_inode(bdev);
}

static void blkdev_put_whole(struct block_device *bdev)
{
        if (atomic_dec_and_test(&bdev->bd_openers))
                blkdev_flush_mapping(bdev);
        if (bdev->bd_disk->fops->release)
                bdev->bd_disk->fops->release(bdev->bd_disk);
}

static int blkdev_get_whole(struct block_device *bdev, blk_mode_t mode)
{
        struct gendisk *disk = bdev->bd_disk;
        int ret;

        if (disk->fops->open) {
                ret = disk->fops->open(disk, mode);
                if (ret) {
                        /* avoid ghost partitions on a removed medium */
                        if (ret == -ENOMEDIUM &&
                             test_bit(GD_NEED_PART_SCAN, &disk->state))
                                bdev_disk_changed(disk, true);
                        return ret;
                }
        }

        if (!atomic_read(&bdev->bd_openers))
                set_init_blocksize(bdev);
        atomic_inc(&bdev->bd_openers);
        if (test_bit(GD_NEED_PART_SCAN, &disk->state)) {
                /*
                 * Only return scanning errors if we are called from contexts
                 * that explicitly want them, e.g. the BLKRRPART ioctl.
                 */
                ret = bdev_disk_changed(disk, false);
                if (ret && (mode & BLK_OPEN_STRICT_SCAN)) {
                        blkdev_put_whole(bdev);
                        return ret;
                }
        }
        return 0;
}

static int blkdev_get_part(struct block_device *part, blk_mode_t mode)
{
        struct gendisk *disk = part->bd_disk;
        int ret;

        ret = blkdev_get_whole(bdev_whole(part), mode);
        if (ret)
                return ret;

        ret = -ENXIO;
        if (!bdev_nr_sectors(part))
                goto out_blkdev_put;

        if (!atomic_read(&part->bd_openers)) {
                disk->open_partitions++;
                set_init_blocksize(part);
        }
        atomic_inc(&part->bd_openers);
        return 0;

out_blkdev_put:
        blkdev_put_whole(bdev_whole(part));
        return ret;
}

int bdev_permission(dev_t dev, blk_mode_t mode, void *holder)
{
        int ret;

        ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
                        MAJOR(dev), MINOR(dev),
                        ((mode & BLK_OPEN_READ) ? DEVCG_ACC_READ : 0) |
                        ((mode & BLK_OPEN_WRITE) ? DEVCG_ACC_WRITE : 0));
        if (ret)
                return ret;

        /* Blocking writes requires exclusive opener */
        if (mode & BLK_OPEN_RESTRICT_WRITES && !holder)
                return -EINVAL;

        /*
         * We're using error pointers to indicate to ->release() when we
         * failed to open that block device. Also this doesn't make sense.
         */
        if (WARN_ON_ONCE(IS_ERR(holder)))
                return -EINVAL;

        return 0;
}

static void blkdev_put_part(struct block_device *part)
{
        struct block_device *whole = bdev_whole(part);

        if (atomic_dec_and_test(&part->bd_openers)) {
                blkdev_flush_mapping(part);
                whole->bd_disk->open_partitions--;
        }
        blkdev_put_whole(whole);
}

struct block_device *blkdev_get_no_open(dev_t dev, bool autoload)
{
        struct block_device *bdev;
        struct inode *inode;

        inode = ilookup(blockdev_superblock, dev);
        if (!inode && autoload && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) {
                blk_request_module(dev);
                inode = ilookup(blockdev_superblock, dev);
                if (inode)
                        pr_warn_ratelimited(
"block device autoloading is deprecated and will be removed.\n");
        }
        if (!inode)
                return NULL;

        /* switch from the inode reference to a device mode one: */
        bdev = &BDEV_I(inode)->bdev;
        if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
                bdev = NULL;
        iput(inode);
        return bdev;
}

void blkdev_put_no_open(struct block_device *bdev)
{
        put_device(&bdev->bd_device);
}

static bool bdev_writes_blocked(struct block_device *bdev)
{
        return bdev->bd_writers < 0;
}

static void bdev_block_writes(struct block_device *bdev)
{
        bdev->bd_writers--;
}

static void bdev_unblock_writes(struct block_device *bdev)
{
        bdev->bd_writers++;
}

static bool bdev_may_open(struct block_device *bdev, blk_mode_t mode)
{
        if (bdev_allow_write_mounted)
                return true;
        /* Writes blocked? */
        if (mode & BLK_OPEN_WRITE && bdev_writes_blocked(bdev))
                return false;
        if (mode & BLK_OPEN_RESTRICT_WRITES && bdev->bd_writers > 0)
                return false;
        return true;
}

static void bdev_claim_write_access(struct block_device *bdev, blk_mode_t mode)
{
        if (bdev_allow_write_mounted)
                return;

        /* Claim exclusive or shared write access. */
        if (mode & BLK_OPEN_RESTRICT_WRITES)
                bdev_block_writes(bdev);
        else if (mode & BLK_OPEN_WRITE)
                bdev->bd_writers++;
}

static inline bool bdev_unclaimed(const struct file *bdev_file)
{
        return bdev_file->private_data == BDEV_I(bdev_file->f_mapping->host);
}

static void bdev_yield_write_access(struct file *bdev_file)
{
        struct block_device *bdev;

        if (bdev_allow_write_mounted)
                return;

        if (bdev_unclaimed(bdev_file))
                return;

        bdev = file_bdev(bdev_file);

        if (bdev_file->f_mode & FMODE_WRITE_RESTRICTED)
                bdev_unblock_writes(bdev);
        else if (bdev_file->f_mode & FMODE_WRITE)
                bdev->bd_writers--;
}

/**
 * bdev_open - open a block device
 * @bdev: block device to open
 * @mode: open mode (BLK_OPEN_*)
 * @holder: exclusive holder identifier
 * @hops: holder operations
 * @bdev_file: file for the block device
 *
 * Open the block device. If @holder is not %NULL, the block device is opened
 * with exclusive access.  Exclusive opens may nest for the same @holder.
 *
 * CONTEXT:
 * Might sleep.
 *
 * RETURNS:
 * zero on success, -errno on failure.
 */
int bdev_open(struct block_device *bdev, blk_mode_t mode, void *holder,
              const struct blk_holder_ops *hops, struct file *bdev_file)
{
        bool unblock_events = true;
        struct gendisk *disk = bdev->bd_disk;
        int ret;

        if (holder) {
                mode |= BLK_OPEN_EXCL;
                ret = bd_prepare_to_claim(bdev, holder, hops);
                if (ret)
                        return ret;
        } else {
                if (WARN_ON_ONCE(mode & BLK_OPEN_EXCL))
                        return -EIO;
        }

        disk_block_events(disk);

        mutex_lock(&disk->open_mutex);
        ret = -ENXIO;
        if (!disk_live(disk))
                goto abort_claiming;
        if (!try_module_get(disk->fops->owner))
                goto abort_claiming;
        ret = -EBUSY;
        if (!bdev_may_open(bdev, mode))
                goto put_module;
        if (bdev_is_partition(bdev))
                ret = blkdev_get_part(bdev, mode);
        else
                ret = blkdev_get_whole(bdev, mode);
        if (ret)
                goto put_module;
        bdev_claim_write_access(bdev, mode);
        if (holder) {
                bd_finish_claiming(bdev, holder, hops);

                /*
                 * Block event polling for write claims if requested.  Any write
                 * holder makes the write_holder state stick until all are
                 * released.  This is good enough and tracking individual
                 * writeable reference is too fragile given the way @mode is
                 * used in blkdev_get/put().
                 */
                if ((mode & BLK_OPEN_WRITE) &&
                    !bdev_test_flag(bdev, BD_WRITE_HOLDER) &&
                    (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
                        bdev_set_flag(bdev, BD_WRITE_HOLDER);
                        unblock_events = false;
                }
        }
        mutex_unlock(&disk->open_mutex);

        if (unblock_events)
                disk_unblock_events(disk);

        bdev_file->f_flags |= O_LARGEFILE;
        bdev_file->f_mode |= FMODE_CAN_ODIRECT;
        if (bdev_nowait(bdev))
                bdev_file->f_mode |= FMODE_NOWAIT;
        if (mode & BLK_OPEN_RESTRICT_WRITES)
                bdev_file->f_mode |= FMODE_WRITE_RESTRICTED;
        bdev_file->f_mapping = bdev->bd_mapping;
        bdev_file->f_wb_err = filemap_sample_wb_err(bdev_file->f_mapping);
        bdev_file->private_data = holder;

        return 0;
put_module:
        module_put(disk->fops->owner);
abort_claiming:
        if (holder)
                bd_abort_claiming(bdev, holder);
        mutex_unlock(&disk->open_mutex);
        disk_unblock_events(disk);
        return ret;
}

/*
 * If BLK_OPEN_WRITE_IOCTL is set then this is a historical quirk
 * associated with the floppy driver where it has allowed ioctls if the
 * file was opened for writing, but does not allow reads or writes.
 * Make sure that this quirk is reflected in @f_flags.
 *
 * It can also happen if a block device is opened as O_RDWR | O_WRONLY.
 */
static unsigned blk_to_file_flags(blk_mode_t mode)
{
        unsigned int flags = 0;

        if ((mode & (BLK_OPEN_READ | BLK_OPEN_WRITE)) ==
            (BLK_OPEN_READ | BLK_OPEN_WRITE))
                flags |= O_RDWR;
        else if (mode & BLK_OPEN_WRITE_IOCTL)
                flags |= O_RDWR | O_WRONLY;
        else if (mode & BLK_OPEN_WRITE)
                flags |= O_WRONLY;
        else if (mode & BLK_OPEN_READ)
                flags |= O_RDONLY; /* homeopathic, because O_RDONLY is 0 */
        else
                WARN_ON_ONCE(true);

        if (mode & BLK_OPEN_NDELAY)
                flags |= O_NDELAY;

        return flags;
}

struct file *bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
                                   const struct blk_holder_ops *hops)
{
        struct file *bdev_file;
        struct block_device *bdev;
        unsigned int flags;
        int ret;

        ret = bdev_permission(dev, mode, holder);
        if (ret)
                return ERR_PTR(ret);

        bdev = blkdev_get_no_open(dev, true);
        if (!bdev)
                return ERR_PTR(-ENXIO);

        flags = blk_to_file_flags(mode);
        bdev_file = alloc_file_pseudo_noaccount(BD_INODE(bdev),
                        blockdev_mnt, "", flags | O_LARGEFILE, &def_blk_fops);
        if (IS_ERR(bdev_file)) {
                blkdev_put_no_open(bdev);
                return bdev_file;
        }
        ihold(BD_INODE(bdev));

        ret = bdev_open(bdev, mode, holder, hops, bdev_file);
        if (ret) {
                /* We failed to open the block device. Let ->release() know. */
                bdev_file->private_data = ERR_PTR(ret);
                fput(bdev_file);
                return ERR_PTR(ret);
        }
        return bdev_file;
}
EXPORT_SYMBOL(bdev_file_open_by_dev);

struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
                                    void *holder,
                                    const struct blk_holder_ops *hops)
{
        struct file *file;
        dev_t dev;
        int error;

        error = lookup_bdev(path, &dev);
        if (error)
                return ERR_PTR(error);

        file = bdev_file_open_by_dev(dev, mode, holder, hops);
        if (!IS_ERR(file) && (mode & BLK_OPEN_WRITE)) {
                if (bdev_read_only(file_bdev(file))) {
                        fput(file);
                        file = ERR_PTR(-EACCES);
                }
        }

        return file;
}
EXPORT_SYMBOL(bdev_file_open_by_path);

static inline void bd_yield_claim(struct file *bdev_file)
{
        struct block_device *bdev = file_bdev(bdev_file);
        void *holder = bdev_file->private_data;

        lockdep_assert_held(&bdev->bd_disk->open_mutex);

        if (WARN_ON_ONCE(IS_ERR_OR_NULL(holder)))
                return;

        if (!bdev_unclaimed(bdev_file))
                bd_end_claim(bdev, holder);
}

void bdev_release(struct file *bdev_file)
{
        struct block_device *bdev = file_bdev(bdev_file);
        void *holder = bdev_file->private_data;
        struct gendisk *disk = bdev->bd_disk;

        /* We failed to open that block device. */
        if (IS_ERR(holder))
                goto put_no_open;

        /*
         * Sync early if it looks like we're the last one.  If someone else
         * opens the block device between now and the decrement of bd_openers
         * then we did a sync that we didn't need to, but that's not the end
         * of the world and we want to avoid long (could be several minute)
         * syncs while holding the mutex.
         */
        if (atomic_read(&bdev->bd_openers) == 1)
                sync_blockdev(bdev);

        mutex_lock(&disk->open_mutex);
        bdev_yield_write_access(bdev_file);

        if (holder)
                bd_yield_claim(bdev_file);

        /*
         * Trigger event checking and tell drivers to flush MEDIA_CHANGE
         * event.  This is to ensure detection of media removal commanded
         * from userland - e.g. eject(1).
         */
        disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);

        if (bdev_is_partition(bdev))
                blkdev_put_part(bdev);
        else
                blkdev_put_whole(bdev);
        mutex_unlock(&disk->open_mutex);

        module_put(disk->fops->owner);
put_no_open:
        blkdev_put_no_open(bdev);
}

/**
 * bdev_fput - yield claim to the block device and put the file
 * @bdev_file: open block device
 *
 * Yield claim on the block device and put the file. Ensure that the
 * block device can be reclaimed before the file is closed which is a
 * deferred operation.
 */
void bdev_fput(struct file *bdev_file)
{
        if (WARN_ON_ONCE(bdev_file->f_op != &def_blk_fops))
                return;

        if (bdev_file->private_data) {
                struct block_device *bdev = file_bdev(bdev_file);
                struct gendisk *disk = bdev->bd_disk;

                mutex_lock(&disk->open_mutex);
                bdev_yield_write_access(bdev_file);
                bd_yield_claim(bdev_file);
                /*
                 * Tell release we already gave up our hold on the
                 * device and if write restrictions are available that
                 * we already gave up write access to the device.
                 */
                bdev_file->private_data = BDEV_I(bdev_file->f_mapping->host);
                mutex_unlock(&disk->open_mutex);
        }

        fput(bdev_file);
}
EXPORT_SYMBOL(bdev_fput);

/**
 * lookup_bdev() - Look up a struct block_device by name.
 * @pathname: Name of the block device in the filesystem.
 * @dev: Pointer to the block device's dev_t, if found.
 *
 * Lookup the block device's dev_t at @pathname in the current
 * namespace if possible and return it in @dev.
 *
 * Context: May sleep.
 * Return: 0 if succeeded, negative errno otherwise.
 */
int lookup_bdev(const char *pathname, dev_t *dev)
{
        struct inode *inode;
        struct path path;
        int error;

        if (!pathname || !*pathname)
                return -EINVAL;

        error = kern_path(pathname, LOOKUP_FOLLOW, &path);
        if (error)
                return error;

        inode = d_backing_inode(path.dentry);
        error = -ENOTBLK;
        if (!S_ISBLK(inode->i_mode))
                goto out_path_put;
        error = -EACCES;
        if (!may_open_dev(&path))
                goto out_path_put;

        *dev = inode->i_rdev;
        error = 0;
out_path_put:
        path_put(&path);
        return error;
}
EXPORT_SYMBOL(lookup_bdev);

/**
 * bdev_mark_dead - mark a block device as dead
 * @bdev: block device to operate on
 * @surprise: indicate a surprise removal
 *
 * Tell the file system that this devices or media is dead.  If @surprise is set
 * to %true the device or media is already gone, if not we are preparing for an
 * orderly removal.
 *
 * This calls into the file system, which then typicall syncs out all dirty data
 * and writes back inodes and then invalidates any cached data in the inodes on
 * the file system.  In addition we also invalidate the block device mapping.
 */
void bdev_mark_dead(struct block_device *bdev, bool surprise)
{
        mutex_lock(&bdev->bd_holder_lock);
        if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead)
                bdev->bd_holder_ops->mark_dead(bdev, surprise);
        else {
                mutex_unlock(&bdev->bd_holder_lock);
                sync_blockdev(bdev);
        }

        invalidate_bdev(bdev);
}
/*
 * New drivers should not use this directly.  There are some drivers however
 * that needs this for historical reasons. For example, the DASD driver has
 * historically had a shutdown to offline mode that doesn't actually remove the
 * gendisk that otherwise looks a lot like a safe device removal.
 */
EXPORT_SYMBOL_GPL(bdev_mark_dead);

void sync_bdevs(bool wait)
{
        struct inode *inode, *old_inode = NULL;

        spin_lock(&blockdev_superblock->s_inode_list_lock);
        list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
                struct address_space *mapping = inode->i_mapping;
                struct block_device *bdev;

                spin_lock(&inode->i_lock);
                if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE | I_NEW) ||
                    mapping->nrpages == 0) {
                        spin_unlock(&inode->i_lock);
                        continue;
                }
                __iget(inode);
                spin_unlock(&inode->i_lock);
                spin_unlock(&blockdev_superblock->s_inode_list_lock);
                /*
                 * We hold a reference to 'inode' so it couldn't have been
                 * removed from s_inodes list while we dropped the
                 * s_inode_list_lock  We cannot iput the inode now as we can
                 * be holding the last reference and we cannot iput it under
                 * s_inode_list_lock. So we keep the reference and iput it
                 * later.
                 */
                iput(old_inode);
                old_inode = inode;
                bdev = I_BDEV(inode);

                mutex_lock(&bdev->bd_disk->open_mutex);
                if (!atomic_read(&bdev->bd_openers)) {
                        ; /* skip */
                } else if (wait) {
                        /*
                         * We keep the error status of individual mapping so
                         * that applications can catch the writeback error using
                         * fsync(2). See filemap_fdatawait_keep_errors() for
                         * details.
                         */
                        filemap_fdatawait_keep_errors(inode->i_mapping);
                } else {
                        filemap_fdatawrite(inode->i_mapping);
                }
                mutex_unlock(&bdev->bd_disk->open_mutex);

                spin_lock(&blockdev_superblock->s_inode_list_lock);
        }
        spin_unlock(&blockdev_superblock->s_inode_list_lock);
        iput(old_inode);
}

/*
 * Handle STATX_{DIOALIGN, WRITE_ATOMIC} for block devices.
 */
void bdev_statx(const struct path *path, struct kstat *stat, u32 request_mask)
{
        struct block_device *bdev;

        /*
         * Note that d_backing_inode() returns the block device node inode, not
         * the block device's internal inode.  Therefore it is *not* valid to
         * use I_BDEV() here; the block device has to be looked up by i_rdev
         * instead.
         */
        bdev = blkdev_get_no_open(d_backing_inode(path->dentry)->i_rdev, false);
        if (!bdev)
                return;

        if (request_mask & STATX_DIOALIGN) {
                stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
                stat->dio_offset_align = bdev_logical_block_size(bdev);
                stat->result_mask |= STATX_DIOALIGN;
        }

        if (request_mask & STATX_WRITE_ATOMIC && bdev_can_atomic_write(bdev)) {
                struct request_queue *bd_queue = bdev->bd_queue;

                generic_fill_statx_atomic_writes(stat,
                        queue_atomic_write_unit_min_bytes(bd_queue),
                        queue_atomic_write_unit_max_bytes(bd_queue),
                        0);
        }

        stat->blksize = bdev_io_min(bdev);

        blkdev_put_no_open(bdev);
}

bool disk_live(struct gendisk *disk)
{
        return !inode_unhashed(BD_INODE(disk->part0));
}
EXPORT_SYMBOL_GPL(disk_live);

unsigned int block_size(struct block_device *bdev)
{
        return 1 << BD_INODE(bdev)->i_blkbits;
}
EXPORT_SYMBOL_GPL(block_size);

static int __init setup_bdev_allow_write_mounted(char *str)
{
        if (kstrtobool(str, &bdev_allow_write_mounted))
                pr_warn("Invalid option string for bdev_allow_write_mounted:"
                        " '%s'\n", str);
        return 1;
}
__setup("bdev_allow_write_mounted=", setup_bdev_allow_write_mounted);