diff options
Diffstat (limited to 'fs/block_dev.c')
| -rw-r--r-- | fs/block_dev.c | 923 |
1 files changed, 923 insertions, 0 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c new file mode 100644 index 000000000000..d19d07c49ad3 --- /dev/null +++ b/fs/block_dev.c @@ -0,0 +1,923 @@ +/* + * linux/fs/block_dev.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE + */ + +#include <linux/config.h> +#include <linux/init.h> +#include <linux/mm.h> +#include <linux/fcntl.h> +#include <linux/slab.h> +#include <linux/kmod.h> +#include <linux/major.h> +#include <linux/devfs_fs_kernel.h> +#include <linux/smp_lock.h> +#include <linux/highmem.h> +#include <linux/blkdev.h> +#include <linux/module.h> +#include <linux/blkpg.h> +#include <linux/buffer_head.h> +#include <linux/mpage.h> +#include <linux/mount.h> +#include <linux/uio.h> +#include <linux/namei.h> +#include <asm/uaccess.h> + +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); +} + +inline struct block_device *I_BDEV(struct inode *inode) +{ + return &BDEV_I(inode)->bdev; +} + +EXPORT_SYMBOL(I_BDEV); + +static sector_t max_block(struct block_device *bdev) +{ + sector_t retval = ~((sector_t)0); + loff_t sz = i_size_read(bdev->bd_inode); + + if (sz) { + unsigned int size = block_size(bdev); + unsigned int sizebits = blksize_bits(size); + retval = (sz >> sizebits); + } + return retval; +} + +/* Kill _all_ buffers, dirty or not.. */ +static void kill_bdev(struct block_device *bdev) +{ + invalidate_bdev(bdev, 1); + truncate_inode_pages(bdev->bd_inode->i_mapping, 0); +} + +int set_blocksize(struct block_device *bdev, int size) +{ + /* Size must be a power of two, and between 512 and PAGE_SIZE */ + if (size > PAGE_SIZE || size < 512 || (size & (size-1))) + return -EINVAL; + + /* Size cannot be smaller than the size supported by the device */ + if (size < bdev_hardsect_size(bdev)) + return -EINVAL; + + /* Don't change the size if it is same as current */ + if (bdev->bd_block_size != size) { + sync_blockdev(bdev); + bdev->bd_block_size = size; + bdev->bd_inode->i_blkbits = blksize_bits(size); + kill_bdev(bdev); + } + return 0; +} + +EXPORT_SYMBOL(set_blocksize); + +int sb_set_blocksize(struct super_block *sb, int size) +{ + int bits = 9; /* 2^9 = 512 */ + + if (set_blocksize(sb->s_bdev, size)) + return 0; + /* If we get here, we know size is power of two + * and it's value is between 512 and PAGE_SIZE */ + sb->s_blocksize = size; + for (size >>= 10; size; size >>= 1) + ++bits; + sb->s_blocksize_bits = bits; + return sb->s_blocksize; +} + +EXPORT_SYMBOL(sb_set_blocksize); + +int sb_min_blocksize(struct super_block *sb, int size) +{ + int minsize = bdev_hardsect_size(sb->s_bdev); + if (size < minsize) + size = minsize; + return sb_set_blocksize(sb, size); +} + +EXPORT_SYMBOL(sb_min_blocksize); + +static int +blkdev_get_block(struct inode *inode, sector_t iblock, + struct buffer_head *bh, int create) +{ + if (iblock >= max_block(I_BDEV(inode))) { + if (create) + return -EIO; + + /* + * for reads, we're just trying to fill a partial page. + * return a hole, they will have to call get_block again + * before they can fill it, and they will get -EIO at that + * time + */ + return 0; + } + bh->b_bdev = I_BDEV(inode); + bh->b_blocknr = iblock; + set_buffer_mapped(bh); + return 0; +} + +static int +blkdev_get_blocks(struct inode *inode, sector_t iblock, + unsigned long max_blocks, struct buffer_head *bh, int create) +{ + sector_t end_block = max_block(I_BDEV(inode)); + + if ((iblock + max_blocks) > end_block) { + max_blocks = end_block - iblock; + if ((long)max_blocks <= 0) { + if (create) + return -EIO; /* write fully beyond EOF */ + /* + * It is a read which is fully beyond EOF. We return + * a !buffer_mapped buffer + */ + max_blocks = 0; + } + } + + bh->b_bdev = I_BDEV(inode); + bh->b_blocknr = iblock; + bh->b_size = max_blocks << inode->i_blkbits; + if (max_blocks) + set_buffer_mapped(bh); + return 0; +} + +static ssize_t +blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, + loff_t offset, unsigned long nr_segs) +{ + struct file *file = iocb->ki_filp; + struct inode *inode = file->f_mapping->host; + + return blockdev_direct_IO_no_locking(rw, iocb, inode, I_BDEV(inode), + iov, offset, nr_segs, blkdev_get_blocks, NULL); +} + +static int blkdev_writepage(struct page *page, struct writeback_control *wbc) +{ + return block_write_full_page(page, blkdev_get_block, wbc); +} + +static int blkdev_readpage(struct file * file, struct page * page) +{ + return block_read_full_page(page, blkdev_get_block); +} + +static int blkdev_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to) +{ + return block_prepare_write(page, from, to, blkdev_get_block); +} + +static int blkdev_commit_write(struct file *file, struct page *page, unsigned from, unsigned to) +{ + return block_commit_write(page, from, to); +} + +/* + * private llseek: + * for a block special file file->f_dentry->d_inode->i_size is zero + * so we compute the size by hand (just as in block_read/write above) + */ +static loff_t block_llseek(struct file *file, loff_t offset, int origin) +{ + struct inode *bd_inode = file->f_mapping->host; + loff_t size; + loff_t retval; + + down(&bd_inode->i_sem); + size = i_size_read(bd_inode); + + switch (origin) { + case 2: + offset += size; + break; + case 1: + offset += file->f_pos; + } + retval = -EINVAL; + if (offset >= 0 && offset <= size) { + if (offset != file->f_pos) { + file->f_pos = offset; + } + retval = offset; + } + up(&bd_inode->i_sem); + return retval; +} + +/* + * Filp is never NULL; the only case when ->fsync() is called with + * NULL first argument is nfsd_sync_dir() and that's not a directory. + */ + +static int block_fsync(struct file *filp, struct dentry *dentry, int datasync) +{ + return sync_blockdev(I_BDEV(filp->f_mapping->host)); +} + +/* + * pseudo-fs + */ + +static __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock); +static kmem_cache_t * bdev_cachep; + +static struct inode *bdev_alloc_inode(struct super_block *sb) +{ + struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, SLAB_KERNEL); + if (!ei) + return NULL; + return &ei->vfs_inode; +} + +static void bdev_destroy_inode(struct inode *inode) +{ + struct bdev_inode *bdi = BDEV_I(inode); + + bdi->bdev.bd_inode_backing_dev_info = NULL; + kmem_cache_free(bdev_cachep, bdi); +} + +static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags) +{ + struct bdev_inode *ei = (struct bdev_inode *) foo; + struct block_device *bdev = &ei->bdev; + + if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == + SLAB_CTOR_CONSTRUCTOR) + { + memset(bdev, 0, sizeof(*bdev)); + sema_init(&bdev->bd_sem, 1); + sema_init(&bdev->bd_mount_sem, 1); + INIT_LIST_HEAD(&bdev->bd_inodes); + INIT_LIST_HEAD(&bdev->bd_list); + inode_init_once(&ei->vfs_inode); + } +} + +static inline void __bd_forget(struct inode *inode) +{ + list_del_init(&inode->i_devices); + inode->i_bdev = NULL; + inode->i_mapping = &inode->i_data; +} + +static void bdev_clear_inode(struct inode *inode) +{ + struct block_device *bdev = &BDEV_I(inode)->bdev; + struct list_head *p; + spin_lock(&bdev_lock); + while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) { + __bd_forget(list_entry(p, struct inode, i_devices)); + } + list_del_init(&bdev->bd_list); + spin_unlock(&bdev_lock); +} + +static struct super_operations bdev_sops = { + .statfs = simple_statfs, + .alloc_inode = bdev_alloc_inode, + .destroy_inode = bdev_destroy_inode, + .drop_inode = generic_delete_inode, + .clear_inode = bdev_clear_inode, +}; + +static struct super_block *bd_get_sb(struct file_system_type *fs_type, + int flags, const char *dev_name, void *data) +{ + return get_sb_pseudo(fs_type, "bdev:", &bdev_sops, 0x62646576); +} + +static struct file_system_type bd_type = { + .name = "bdev", + .get_sb = bd_get_sb, + .kill_sb = kill_anon_super, +}; + +static struct vfsmount *bd_mnt; +struct super_block *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_PANIC, + init_once, NULL); + err = register_filesystem(&bd_type); + if (err) + panic("Cannot register bdev pseudo-fs"); + bd_mnt = kern_mount(&bd_type); + err = PTR_ERR(bd_mnt); + if (IS_ERR(bd_mnt)) + panic("Cannot create bdev pseudo-fs"); + blockdev_superblock = bd_mnt->mnt_sb; /* For writeback */ +} + +/* + * Most likely _very_ bad one - but then it's hardly critical for small + * /dev and can be fixed when somebody will need really large one. + * Keep in mind that it will be fed through icache hash function too. + */ +static inline unsigned long hash(dev_t dev) +{ + return MAJOR(dev)+MINOR(dev); +} + +static int bdev_test(struct inode *inode, void *data) +{ + return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data; +} + +static int bdev_set(struct inode *inode, void *data) +{ + BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data; + return 0; +} + +static LIST_HEAD(all_bdevs); + +struct block_device *bdget(dev_t dev) +{ + struct block_device *bdev; + struct inode *inode; + + inode = iget5_locked(bd_mnt->mnt_sb, hash(dev), + bdev_test, bdev_set, &dev); + + if (!inode) + return NULL; + + bdev = &BDEV_I(inode)->bdev; + + if (inode->i_state & I_NEW) { + bdev->bd_contains = NULL; + bdev->bd_inode = inode; + bdev->bd_block_size = (1 << inode->i_blkbits); + bdev->bd_part_count = 0; + bdev->bd_invalidated = 0; + inode->i_mode = S_IFBLK; + inode->i_rdev = dev; + inode->i_bdev = bdev; + inode->i_data.a_ops = &def_blk_aops; + mapping_set_gfp_mask(&inode->i_data, GFP_USER); + inode->i_data.backing_dev_info = &default_backing_dev_info; + spin_lock(&bdev_lock); + list_add(&bdev->bd_list, &all_bdevs); + spin_unlock(&bdev_lock); + unlock_new_inode(inode); + } + return bdev; +} + +EXPORT_SYMBOL(bdget); + +long nr_blockdev_pages(void) +{ + struct list_head *p; + long ret = 0; + spin_lock(&bdev_lock); + list_for_each(p, &all_bdevs) { + struct block_device *bdev; + bdev = list_entry(p, struct block_device, bd_list); + ret += bdev->bd_inode->i_mapping->nrpages; + } + spin_unlock(&bdev_lock); + return ret; +} + +void bdput(struct block_device *bdev) +{ + iput(bdev->bd_inode); +} + +EXPORT_SYMBOL(bdput); + +static struct block_device *bd_acquire(struct inode *inode) +{ + struct block_device *bdev; + spin_lock(&bdev_lock); + bdev = inode->i_bdev; + if (bdev && igrab(bdev->bd_inode)) { + spin_unlock(&bdev_lock); + return bdev; + } + spin_unlock(&bdev_lock); + bdev = bdget(inode->i_rdev); + if (bdev) { + spin_lock(&bdev_lock); + if (inode->i_bdev) + __bd_forget(inode); + inode->i_bdev = bdev; + inode->i_mapping = bdev->bd_inode->i_mapping; + list_add(&inode->i_devices, &bdev->bd_inodes); + spin_unlock(&bdev_lock); + } + return bdev; +} + +/* Call when you free inode */ + +void bd_forget(struct inode *inode) +{ + spin_lock(&bdev_lock); + if (inode->i_bdev) + __bd_forget(inode); + spin_unlock(&bdev_lock); +} + +int bd_claim(struct block_device *bdev, void *holder) +{ + int res; + spin_lock(&bdev_lock); + + /* first decide result */ + if (bdev->bd_holder == holder) + res = 0; /* already a holder */ + else if (bdev->bd_holder != NULL) + res = -EBUSY; /* held by someone else */ + else if (bdev->bd_contains == bdev) + res = 0; /* is a whole device which isn't held */ + + else if (bdev->bd_contains->bd_holder == bd_claim) + res = 0; /* is a partition of a device that is being partitioned */ + else if (bdev->bd_contains->bd_holder != NULL) + res = -EBUSY; /* is a partition of a held device */ + else + res = 0; /* is a partition of an un-held device */ + + /* now impose change */ + if (res==0) { + /* note that for a whole device bd_holders + * will be incremented twice, and bd_holder will + * be set to bd_claim before being set to holder + */ + bdev->bd_contains->bd_holders ++; + bdev->bd_contains->bd_holder = bd_claim; + bdev->bd_holders++; + bdev->bd_holder = holder; + } + spin_unlock(&bdev_lock); + return res; +} + +EXPORT_SYMBOL(bd_claim); + +void bd_release(struct block_device *bdev) +{ + spin_lock(&bdev_lock); + if (!--bdev->bd_contains->bd_holders) + bdev->bd_contains->bd_holder = NULL; + if (!--bdev->bd_holders) + bdev->bd_holder = NULL; + spin_unlock(&bdev_lock); +} + +EXPORT_SYMBOL(bd_release); + +/* + * Tries to open block device by device number. Use it ONLY if you + * really do not have anything better - i.e. when you are behind a + * truly sucky interface and all you are given is a device number. _Never_ + * to be used for internal purposes. If you ever need it - reconsider + * your API. + */ +struct block_device *open_by_devnum(dev_t dev, unsigned mode) +{ + struct block_device *bdev = bdget(dev); + int err = -ENOMEM; + int flags = mode & FMODE_WRITE ? O_RDWR : O_RDONLY; + if (bdev) + err = blkdev_get(bdev, mode, flags); + return err ? ERR_PTR(err) : bdev; +} + +EXPORT_SYMBOL(open_by_devnum); + +/* + * This routine checks whether a removable media has been changed, + * and invalidates all buffer-cache-entries in that case. This + * is a relatively slow routine, so we have to try to minimize using + * it. Thus it is called only upon a 'mount' or 'open'. This + * is the best way of combining speed and utility, I think. + * People changing diskettes in the middle of an operation deserve + * to lose :-) + */ +int check_disk_change(struct block_device *bdev) +{ + struct gendisk *disk = bdev->bd_disk; + struct block_device_operations * bdops = disk->fops; + + if (!bdops->media_changed) + return 0; + if (!bdops->media_changed(bdev->bd_disk)) + return 0; + + if (__invalidate_device(bdev, 0)) + printk("VFS: busy inodes on changed media.\n"); + + if (bdops->revalidate_disk) + bdops->revalidate_disk(bdev->bd_disk); + if (bdev->bd_disk->minors > 1) + bdev->bd_invalidated = 1; + return 1; +} + +EXPORT_SYMBOL(check_disk_change); + +void bd_set_size(struct block_device *bdev, loff_t size) +{ + unsigned bsize = bdev_hardsect_size(bdev); + + bdev->bd_inode->i_size = size; + while (bsize < PAGE_CACHE_SIZE) { + if (size & bsize) + break; + bsize <<= 1; + } + bdev->bd_block_size = bsize; + bdev->bd_inode->i_blkbits = blksize_bits(bsize); +} +EXPORT_SYMBOL(bd_set_size); + +static int do_open(struct block_device *bdev, struct file *file) +{ + struct module *owner = NULL; + struct gendisk *disk; + int ret = -ENXIO; + int part; + + file->f_mapping = bdev->bd_inode->i_mapping; + lock_kernel(); + disk = get_gendisk(bdev->bd_dev, &part); + if (!disk) { + unlock_kernel(); + bdput(bdev); + return ret; + } + owner = disk->fops->owner; + + down(&bdev->bd_sem); + if (!bdev->bd_openers) { + bdev->bd_disk = disk; + bdev->bd_contains = bdev; + if (!part) { + struct backing_dev_info *bdi; + if (disk->fops->open) { + ret = disk->fops->open(bdev->bd_inode, file); + if (ret) + goto out_first; + } + if (!bdev->bd_openers) { + bd_set_size(bdev,(loff_t)get_capacity(disk)<<9); + bdi = blk_get_backing_dev_info(bdev); + if (bdi == NULL) + bdi = &default_backing_dev_info; + bdev->bd_inode->i_data.backing_dev_info = bdi; + } + if (bdev->bd_invalidated) + rescan_partitions(disk, bdev); + } else { + struct hd_struct *p; + struct block_device *whole; + whole = bdget_disk(disk, 0); + ret = -ENOMEM; + if (!whole) + goto out_first; + ret = blkdev_get(whole, file->f_mode, file->f_flags); + if (ret) + goto out_first; + bdev->bd_contains = whole; + down(&whole->bd_sem); + whole->bd_part_count++; + p = disk->part[part - 1]; + bdev->bd_inode->i_data.backing_dev_info = + whole->bd_inode->i_data.backing_dev_info; + if (!(disk->flags & GENHD_FL_UP) || !p || !p->nr_sects) { + whole->bd_part_count--; + up(&whole->bd_sem); + ret = -ENXIO; + goto out_first; + } + kobject_get(&p->kobj); + bdev->bd_part = p; + bd_set_size(bdev, (loff_t) p->nr_sects << 9); + up(&whole->bd_sem); + } + } else { + put_disk(disk); + module_put(owner); + if (bdev->bd_contains == bdev) { + if (bdev->bd_disk->fops->open) { + ret = bdev->bd_disk->fops->open(bdev->bd_inode, file); + if (ret) + goto out; + } + if (bdev->bd_invalidated) + rescan_partitions(bdev->bd_disk, bdev); + } else { + down(&bdev->bd_contains->bd_sem); + bdev->bd_contains->bd_part_count++; + up(&bdev->bd_contains->bd_sem); + } + } + bdev->bd_openers++; + up(&bdev->bd_sem); + unlock_kernel(); + return 0; + +out_first: + bdev->bd_disk = NULL; + bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; + if (bdev != bdev->bd_contains) + blkdev_put(bdev->bd_contains); + bdev->bd_contains = NULL; + put_disk(disk); + module_put(owner); +out: + up(&bdev->bd_sem); + unlock_kernel(); + if (ret) + bdput(bdev); + return ret; +} + +int blkdev_get(struct block_device *bdev, mode_t mode, unsigned flags) +{ + /* + * This crockload is due to bad choice of ->open() type. + * It will go away. + * For now, block device ->open() routine must _not_ + * examine anything in 'inode' argument except ->i_rdev. + */ + struct file fake_file = {}; + struct dentry fake_dentry = {}; + fake_file.f_mode = mode; + fake_file.f_flags = flags; + fake_file.f_dentry = &fake_dentry; + fake_dentry.d_inode = bdev->bd_inode; + + return do_open(bdev, &fake_file); +} + +EXPORT_SYMBOL(blkdev_get); + +static int blkdev_open(struct inode * inode, struct file * filp) +{ + struct block_device *bdev; + int res; + + /* + * Preserve backwards compatibility and allow large file access + * even if userspace doesn't ask for it explicitly. Some mkfs + * binary needs it. We might want to drop this workaround + * during an unstable branch. + */ + filp->f_flags |= O_LARGEFILE; + + bdev = bd_acquire(inode); + + res = do_open(bdev, filp); + if (res) + return res; + + if (!(filp->f_flags & O_EXCL) ) + return 0; + + if (!(res = bd_claim(bdev, filp))) + return 0; + + blkdev_put(bdev); + return res; +} + +int blkdev_put(struct block_device *bdev) +{ + int ret = 0; + struct inode *bd_inode = bdev->bd_inode; + struct gendisk *disk = bdev->bd_disk; + + down(&bdev->bd_sem); + lock_kernel(); + if (!--bdev->bd_openers) { + sync_blockdev(bdev); + kill_bdev(bdev); + } + if (bdev->bd_contains == bdev) { + if (disk->fops->release) + ret = disk->fops->release(bd_inode, NULL); + } else { + down(&bdev->bd_contains->bd_sem); + bdev->bd_contains->bd_part_count--; + up(&bdev->bd_contains->bd_sem); + } + if (!bdev->bd_openers) { + struct module *owner = disk->fops->owner; + + put_disk(disk); + module_put(owner); + + if (bdev->bd_contains != bdev) { + kobject_put(&bdev->bd_part->kobj); + bdev->bd_part = NULL; + } + bdev->bd_disk = NULL; + bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info; + if (bdev != bdev->bd_contains) { + blkdev_put(bdev->bd_contains); + } + bdev->bd_contains = NULL; + } + unlock_kernel(); + up(&bdev->bd_sem); + bdput(bdev); + return ret; +} + +EXPORT_SYMBOL(blkdev_put); + +static int blkdev_close(struct inode * inode, struct file * filp) +{ + struct block_device *bdev = I_BDEV(filp->f_mapping->host); + if (bdev->bd_holder == filp) + bd_release(bdev); + return blkdev_put(bdev); +} + +static ssize_t blkdev_file_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct iovec local_iov = { .iov_base = (void __user *)buf, .iov_len = count }; + + return generic_file_write_nolock(file, &local_iov, 1, ppos); +} + +static ssize_t blkdev_file_aio_write(struct kiocb *iocb, const char __user *buf, + size_t count, loff_t pos) +{ + struct iovec local_iov = { .iov_base = (void __user *)buf, .iov_len = count }; + + return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos); +} + +static int block_ioctl(struct inode *inode, struct file *file, unsigned cmd, + unsigned long arg) +{ + return blkdev_ioctl(file->f_mapping->host, file, cmd, arg); +} + +struct address_space_operations def_blk_aops = { + .readpage = blkdev_readpage, + .writepage = blkdev_writepage, + .sync_page = block_sync_page, + .prepare_write = blkdev_prepare_write, + .commit_write = blkdev_commit_write, + .writepages = generic_writepages, + .direct_IO = blkdev_direct_IO, +}; + +struct file_operations def_blk_fops = { + .open = blkdev_open, + .release = blkdev_close, + .llseek = block_llseek, + .read = generic_file_read, + .write = blkdev_file_write, + .aio_read = generic_file_aio_read, + .aio_write = blkdev_file_aio_write, + .mmap = generic_file_mmap, + .fsync = block_fsync, + .ioctl = block_ioctl, +#ifdef CONFIG_COMPAT + .compat_ioctl = compat_blkdev_ioctl, +#endif + .readv = generic_file_readv, + .writev = generic_file_write_nolock, + .sendfile = generic_file_sendfile, +}; + +int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg) +{ + int res; + mm_segment_t old_fs = get_fs(); + set_fs(KERNEL_DS); + res = blkdev_ioctl(bdev->bd_inode, NULL, cmd, arg); + set_fs(old_fs); + return res; +} + +EXPORT_SYMBOL(ioctl_by_bdev); + +/** + * lookup_bdev - lookup a struct block_device by name + * + * @path: special file representing the block device + * + * Get a reference to the blockdevice at @path in the current + * namespace if possible and return it. Return ERR_PTR(error) + * otherwise. + */ +struct block_device *lookup_bdev(const char *path) +{ + struct block_device *bdev; + struct inode *inode; + struct nameidata nd; + int error; + + if (!path || !*path) + return ERR_PTR(-EINVAL); + + error = path_lookup(path, LOOKUP_FOLLOW, &nd); + if (error) + return ERR_PTR(error); + + inode = nd.dentry->d_inode; + error = -ENOTBLK; + if (!S_ISBLK(inode->i_mode)) + goto fail; + error = -EACCES; + if (nd.mnt->mnt_flags & MNT_NODEV) + goto fail; + error = -ENOMEM; + bdev = bd_acquire(inode); + if (!bdev) + goto fail; +out: + path_release(&nd); + return bdev; +fail: + bdev = ERR_PTR(error); + goto out; +} + +/** + * open_bdev_excl - open a block device by name and set it up for use + * + * @path: special file representing the block device + * @flags: %MS_RDONLY for opening read-only + * @holder: owner for exclusion + * + * Open the blockdevice described by the special file at @path, claim it + * for the @holder. + */ +struct block_device *open_bdev_excl(const char *path, int flags, void *holder) +{ + struct block_device *bdev; + mode_t mode = FMODE_READ; + int error = 0; + + bdev = lookup_bdev(path); + if (IS_ERR(bdev)) + return bdev; + + if (!(flags & MS_RDONLY)) + mode |= FMODE_WRITE; + error = blkdev_get(bdev, mode, 0); + if (error) + return ERR_PTR(error); + error = -EACCES; + if (!(flags & MS_RDONLY) && bdev_read_only(bdev)) + goto blkdev_put; + error = bd_claim(bdev, holder); + if (error) + goto blkdev_put; + + return bdev; + +blkdev_put: + blkdev_put(bdev); + return ERR_PTR(error); +} + +EXPORT_SYMBOL(open_bdev_excl); + +/** + * close_bdev_excl - release a blockdevice openen by open_bdev_excl() + * + * @bdev: blockdevice to close + * + * This is the counterpart to open_bdev_excl(). + */ +void close_bdev_excl(struct block_device *bdev) +{ + bd_release(bdev); + blkdev_put(bdev); +} + +EXPORT_SYMBOL(close_bdev_excl); |