KVM: remove more traces of device assignment UAPI

[thirdparty/kernel/stable.git] / block / fops.c

// 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/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/uio.h>
#include <linux/namei.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/falloc.h>
#include <linux/suspend.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/module.h>
#include "blk.h"

static inline struct inode *bdev_file_inode(struct file *file)
{
        return file->f_mapping->host;
}

static blk_opf_t dio_bio_write_op(struct kiocb *iocb)
{
        blk_opf_t opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;

        /* avoid the need for a I/O completion work item */
        if (iocb_is_dsync(iocb))
                opf |= REQ_FUA;
        return opf;
}

static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos,
                              struct iov_iter *iter)
{
        return pos & (bdev_logical_block_size(bdev) - 1) ||
                !bdev_iter_is_aligned(bdev, iter);
}

#define DIO_INLINE_BIO_VECS 4

static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
                struct iov_iter *iter, unsigned int nr_pages)
{
        struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
        struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs;
        loff_t pos = iocb->ki_pos;
        bool should_dirty = false;
        struct bio bio;
        ssize_t ret;

        if (blkdev_dio_unaligned(bdev, pos, iter))
                return -EINVAL;

        if (nr_pages <= DIO_INLINE_BIO_VECS)
                vecs = inline_vecs;
        else {
                vecs = kmalloc_array(nr_pages, sizeof(struct bio_vec),
                                     GFP_KERNEL);
                if (!vecs)
                        return -ENOMEM;
        }

        if (iov_iter_rw(iter) == READ) {
                bio_init(&bio, bdev, vecs, nr_pages, REQ_OP_READ);
                if (user_backed_iter(iter))
                        should_dirty = true;
        } else {
                bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb));
        }
        bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;
        bio.bi_ioprio = iocb->ki_ioprio;

        ret = bio_iov_iter_get_pages(&bio, iter);
        if (unlikely(ret))
                goto out;
        ret = bio.bi_iter.bi_size;

        if (iov_iter_rw(iter) == WRITE)
                task_io_account_write(ret);

        if (iocb->ki_flags & IOCB_NOWAIT)
                bio.bi_opf |= REQ_NOWAIT;

        submit_bio_wait(&bio);

        bio_release_pages(&bio, should_dirty);
        if (unlikely(bio.bi_status))
                ret = blk_status_to_errno(bio.bi_status);

out:
        if (vecs != inline_vecs)
                kfree(vecs);

        bio_uninit(&bio);

        return ret;
}

enum {
        DIO_SHOULD_DIRTY        = 1,
        DIO_IS_SYNC             = 2,
};

struct blkdev_dio {
        union {
                struct kiocb            *iocb;
                struct task_struct      *waiter;
        };
        size_t                  size;
        atomic_t                ref;
        unsigned int            flags;
        struct bio              bio ____cacheline_aligned_in_smp;
};

static struct bio_set blkdev_dio_pool;

static void blkdev_bio_end_io(struct bio *bio)
{
        struct blkdev_dio *dio = bio->bi_private;
        bool should_dirty = dio->flags & DIO_SHOULD_DIRTY;

        if (bio->bi_status && !dio->bio.bi_status)
                dio->bio.bi_status = bio->bi_status;

        if (atomic_dec_and_test(&dio->ref)) {
                if (!(dio->flags & DIO_IS_SYNC)) {
                        struct kiocb *iocb = dio->iocb;
                        ssize_t ret;

                        WRITE_ONCE(iocb->private, NULL);

                        if (likely(!dio->bio.bi_status)) {
                                ret = dio->size;
                                iocb->ki_pos += ret;
                        } else {
                                ret = blk_status_to_errno(dio->bio.bi_status);
                        }

                        dio->iocb->ki_complete(iocb, ret);
                        bio_put(&dio->bio);
                } else {
                        struct task_struct *waiter = dio->waiter;

                        WRITE_ONCE(dio->waiter, NULL);
                        blk_wake_io_task(waiter);
                }
        }

        if (should_dirty) {
                bio_check_pages_dirty(bio);
        } else {
                bio_release_pages(bio, false);
                bio_put(bio);
        }
}

static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
                unsigned int nr_pages)
{
        struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
        struct blk_plug plug;
        struct blkdev_dio *dio;
        struct bio *bio;
        bool is_read = (iov_iter_rw(iter) == READ), is_sync;
        blk_opf_t opf = is_read ? REQ_OP_READ : dio_bio_write_op(iocb);
        loff_t pos = iocb->ki_pos;
        int ret = 0;

        if (blkdev_dio_unaligned(bdev, pos, iter))
                return -EINVAL;

        if (iocb->ki_flags & IOCB_ALLOC_CACHE)
                opf |= REQ_ALLOC_CACHE;
        bio = bio_alloc_bioset(bdev, nr_pages, opf, GFP_KERNEL,
                               &blkdev_dio_pool);
        dio = container_of(bio, struct blkdev_dio, bio);
        atomic_set(&dio->ref, 1);
        /*
         * Grab an extra reference to ensure the dio structure which is embedded
         * into the first bio stays around.
         */
        bio_get(bio);

        is_sync = is_sync_kiocb(iocb);
        if (is_sync) {
                dio->flags = DIO_IS_SYNC;
                dio->waiter = current;
        } else {
                dio->flags = 0;
                dio->iocb = iocb;
        }

        dio->size = 0;
        if (is_read && user_backed_iter(iter))
                dio->flags |= DIO_SHOULD_DIRTY;

        blk_start_plug(&plug);

        for (;;) {
                bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
                bio->bi_private = dio;
                bio->bi_end_io = blkdev_bio_end_io;
                bio->bi_ioprio = iocb->ki_ioprio;

                ret = bio_iov_iter_get_pages(bio, iter);
                if (unlikely(ret)) {
                        bio->bi_status = BLK_STS_IOERR;
                        bio_endio(bio);
                        break;
                }
                if (iocb->ki_flags & IOCB_NOWAIT) {
                        /*
                         * This is nonblocking IO, and we need to allocate
                         * another bio if we have data left to map. As we
                         * cannot guarantee that one of the sub bios will not
                         * fail getting issued FOR NOWAIT and as error results
                         * are coalesced across all of them, be safe and ask for
                         * a retry of this from blocking context.
                         */
                        if (unlikely(iov_iter_count(iter))) {
                                bio_release_pages(bio, false);
                                bio_clear_flag(bio, BIO_REFFED);
                                bio_put(bio);
                                blk_finish_plug(&plug);
                                return -EAGAIN;
                        }
                        bio->bi_opf |= REQ_NOWAIT;
                }

                if (is_read) {
                        if (dio->flags & DIO_SHOULD_DIRTY)
                                bio_set_pages_dirty(bio);
                } else {
                        task_io_account_write(bio->bi_iter.bi_size);
                }
                dio->size += bio->bi_iter.bi_size;
                pos += bio->bi_iter.bi_size;

                nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS);
                if (!nr_pages) {
                        submit_bio(bio);
                        break;
                }
                atomic_inc(&dio->ref);
                submit_bio(bio);
                bio = bio_alloc(bdev, nr_pages, opf, GFP_KERNEL);
        }

        blk_finish_plug(&plug);

        if (!is_sync)
                return -EIOCBQUEUED;

        for (;;) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                if (!READ_ONCE(dio->waiter))
                        break;
                blk_io_schedule();
        }
        __set_current_state(TASK_RUNNING);

        if (!ret)
                ret = blk_status_to_errno(dio->bio.bi_status);
        if (likely(!ret))
                ret = dio->size;

        bio_put(&dio->bio);
        return ret;
}

static void blkdev_bio_end_io_async(struct bio *bio)
{
        struct blkdev_dio *dio = container_of(bio, struct blkdev_dio, bio);
        struct kiocb *iocb = dio->iocb;
        ssize_t ret;

        WRITE_ONCE(iocb->private, NULL);

        if (likely(!bio->bi_status)) {
                ret = dio->size;
                iocb->ki_pos += ret;
        } else {
                ret = blk_status_to_errno(bio->bi_status);
        }

        iocb->ki_complete(iocb, ret);

        if (dio->flags & DIO_SHOULD_DIRTY) {
                bio_check_pages_dirty(bio);
        } else {
                bio_release_pages(bio, false);
                bio_put(bio);
        }
}

static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
                                        struct iov_iter *iter,
                                        unsigned int nr_pages)
{
        struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
        bool is_read = iov_iter_rw(iter) == READ;
        blk_opf_t opf = is_read ? REQ_OP_READ : dio_bio_write_op(iocb);
        struct blkdev_dio *dio;
        struct bio *bio;
        loff_t pos = iocb->ki_pos;
        int ret = 0;

        if (blkdev_dio_unaligned(bdev, pos, iter))
                return -EINVAL;

        if (iocb->ki_flags & IOCB_ALLOC_CACHE)
                opf |= REQ_ALLOC_CACHE;
        bio = bio_alloc_bioset(bdev, nr_pages, opf, GFP_KERNEL,
                               &blkdev_dio_pool);
        dio = container_of(bio, struct blkdev_dio, bio);
        dio->flags = 0;
        dio->iocb = iocb;
        bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
        bio->bi_end_io = blkdev_bio_end_io_async;
        bio->bi_ioprio = iocb->ki_ioprio;

        if (iov_iter_is_bvec(iter)) {
                /*
                 * Users don't rely on the iterator being in any particular
                 * state for async I/O returning -EIOCBQUEUED, hence we can
                 * avoid expensive iov_iter_advance(). Bypass
                 * bio_iov_iter_get_pages() and set the bvec directly.
                 */
                bio_iov_bvec_set(bio, iter);
        } else {
                ret = bio_iov_iter_get_pages(bio, iter);
                if (unlikely(ret)) {
                        bio_put(bio);
                        return ret;
                }
        }
        dio->size = bio->bi_iter.bi_size;

        if (is_read) {
                if (user_backed_iter(iter)) {
                        dio->flags |= DIO_SHOULD_DIRTY;
                        bio_set_pages_dirty(bio);
                }
        } else {
                task_io_account_write(bio->bi_iter.bi_size);
        }

        if (iocb->ki_flags & IOCB_NOWAIT)
                bio->bi_opf |= REQ_NOWAIT;

        if (iocb->ki_flags & IOCB_HIPRI) {
                bio->bi_opf |= REQ_POLLED;
                submit_bio(bio);
                WRITE_ONCE(iocb->private, bio);
        } else {
                submit_bio(bio);
        }
        return -EIOCBQUEUED;
}

static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
        unsigned int nr_pages;

        if (!iov_iter_count(iter))
                return 0;

        nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS + 1);
        if (likely(nr_pages <= BIO_MAX_VECS)) {
                if (is_sync_kiocb(iocb))
                        return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
                return __blkdev_direct_IO_async(iocb, iter, nr_pages);
        }
        return __blkdev_direct_IO(iocb, iter, bio_max_segs(nr_pages));
}

static int blkdev_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
{
        struct block_device *bdev = I_BDEV(inode);
        loff_t isize = i_size_read(inode);

        iomap->bdev = bdev;
        iomap->offset = ALIGN_DOWN(offset, bdev_logical_block_size(bdev));
        if (iomap->offset >= isize)
                return -EIO;
        iomap->type = IOMAP_MAPPED;
        iomap->addr = iomap->offset;
        iomap->length = isize - iomap->offset;
        iomap->flags |= IOMAP_F_BUFFER_HEAD; /* noop for !CONFIG_BUFFER_HEAD */
        return 0;
}

static const struct iomap_ops blkdev_iomap_ops = {
        .iomap_begin            = blkdev_iomap_begin,
};

#ifdef CONFIG_BUFFER_HEAD
static int blkdev_get_block(struct inode *inode, sector_t iblock,
                struct buffer_head *bh, int create)
{
        bh->b_bdev = I_BDEV(inode);
        bh->b_blocknr = iblock;
        set_buffer_mapped(bh);
        return 0;
}

/*
 * We cannot call mpage_writepages() as it does not take the buffer lock.
 * We must use block_write_full_folio() directly which holds the buffer
 * lock.  The buffer lock provides the synchronisation with writeback
 * that filesystems rely on when they use the blockdev's mapping.
 */
static int blkdev_writepages(struct address_space *mapping,
                struct writeback_control *wbc)
{
        struct blk_plug plug;
        int err;

        blk_start_plug(&plug);
        err = write_cache_pages(mapping, wbc, block_write_full_folio,
                        blkdev_get_block);
        blk_finish_plug(&plug);

        return err;
}

static int blkdev_read_folio(struct file *file, struct folio *folio)
{
        return block_read_full_folio(folio, blkdev_get_block);
}

static void blkdev_readahead(struct readahead_control *rac)
{
        mpage_readahead(rac, blkdev_get_block);
}

static int blkdev_write_begin(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, struct page **pagep, void **fsdata)
{
        return block_write_begin(mapping, pos, len, pagep, blkdev_get_block);
}

static int blkdev_write_end(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied, struct page *page,
                void *fsdata)
{
        int ret;
        ret = block_write_end(file, mapping, pos, len, copied, page, fsdata);

        unlock_page(page);
        put_page(page);

        return ret;
}

const struct address_space_operations def_blk_aops = {
        .dirty_folio    = block_dirty_folio,
        .invalidate_folio = block_invalidate_folio,
        .read_folio     = blkdev_read_folio,
        .readahead      = blkdev_readahead,
        .writepages     = blkdev_writepages,
        .write_begin    = blkdev_write_begin,
        .write_end      = blkdev_write_end,
        .migrate_folio  = buffer_migrate_folio_norefs,
        .is_dirty_writeback = buffer_check_dirty_writeback,
};
#else /* CONFIG_BUFFER_HEAD */
static int blkdev_read_folio(struct file *file, struct folio *folio)
{
        return iomap_read_folio(folio, &blkdev_iomap_ops);
}

static void blkdev_readahead(struct readahead_control *rac)
{
        iomap_readahead(rac, &blkdev_iomap_ops);
}

static int blkdev_map_blocks(struct iomap_writepage_ctx *wpc,
                struct inode *inode, loff_t offset)
{
        loff_t isize = i_size_read(inode);

        if (WARN_ON_ONCE(offset >= isize))
                return -EIO;
        if (offset >= wpc->iomap.offset &&
            offset < wpc->iomap.offset + wpc->iomap.length)
                return 0;
        return blkdev_iomap_begin(inode, offset, isize - offset,
                                  IOMAP_WRITE, &wpc->iomap, NULL);
}

static const struct iomap_writeback_ops blkdev_writeback_ops = {
        .map_blocks             = blkdev_map_blocks,
};

static int blkdev_writepages(struct address_space *mapping,
                struct writeback_control *wbc)
{
        struct iomap_writepage_ctx wpc = { };

        return iomap_writepages(mapping, wbc, &wpc, &blkdev_writeback_ops);
}

const struct address_space_operations def_blk_aops = {
        .dirty_folio    = filemap_dirty_folio,
        .release_folio          = iomap_release_folio,
        .invalidate_folio       = iomap_invalidate_folio,
        .read_folio             = blkdev_read_folio,
        .readahead              = blkdev_readahead,
        .writepages             = blkdev_writepages,
        .is_partially_uptodate  = iomap_is_partially_uptodate,
        .error_remove_folio     = generic_error_remove_folio,
        .migrate_folio          = filemap_migrate_folio,
};
#endif /* CONFIG_BUFFER_HEAD */

/*
 * for a block special file file_inode(file)->i_size is zero
 * so we compute the size by hand (just as in block_read/write above)
 */
static loff_t blkdev_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *bd_inode = bdev_file_inode(file);
        loff_t retval;

        inode_lock(bd_inode);
        retval = fixed_size_llseek(file, offset, whence, i_size_read(bd_inode));
        inode_unlock(bd_inode);
        return retval;
}

static int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
                int datasync)
{
        struct block_device *bdev = I_BDEV(filp->f_mapping->host);
        int error;

        error = file_write_and_wait_range(filp, start, end);
        if (error)
                return error;

        /*
         * There is no need to serialise calls to blkdev_issue_flush with
         * i_mutex and doing so causes performance issues with concurrent
         * O_SYNC writers to a block device.
         */
        error = blkdev_issue_flush(bdev);
        if (error == -EOPNOTSUPP)
                error = 0;

        return error;
}

/**
 * file_to_blk_mode - get block open flags from file flags
 * @file: file whose open flags should be converted
 *
 * Look at file open flags and generate corresponding block open flags from
 * them. The function works both for file just being open (e.g. during ->open
 * callback) and for file that is already open. This is actually non-trivial
 * (see comment in the function).
 */
blk_mode_t file_to_blk_mode(struct file *file)
{
        blk_mode_t mode = 0;
        struct bdev_handle *handle = file->private_data;

        if (file->f_mode & FMODE_READ)
                mode |= BLK_OPEN_READ;
        if (file->f_mode & FMODE_WRITE)
                mode |= BLK_OPEN_WRITE;
        /*
         * do_dentry_open() clears O_EXCL from f_flags, use handle->mode to
         * determine whether the open was exclusive for already open files.
         */
        if (handle)
                mode |= handle->mode & BLK_OPEN_EXCL;
        else if (file->f_flags & O_EXCL)
                mode |= BLK_OPEN_EXCL;
        if (file->f_flags & O_NDELAY)
                mode |= BLK_OPEN_NDELAY;

        /*
         * If all bits in O_ACCMODE set (aka O_RDWR | O_WRONLY), the floppy
         * driver has historically allowed ioctls as if the file was opened for
         * writing, but does not allow and actual reads or writes.
         */
        if ((file->f_flags & O_ACCMODE) == (O_RDWR | O_WRONLY))
                mode |= BLK_OPEN_WRITE_IOCTL;

        return mode;
}

static int blkdev_open(struct inode *inode, struct file *filp)
{
        struct bdev_handle *handle;
        blk_mode_t mode;

        /*
         * 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;
        filp->f_mode |= FMODE_BUF_RASYNC | FMODE_CAN_ODIRECT;

        mode = file_to_blk_mode(filp);
        handle = bdev_open_by_dev(inode->i_rdev, mode,
                        mode & BLK_OPEN_EXCL ? filp : NULL, NULL);
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (bdev_nowait(handle->bdev))
                filp->f_mode |= FMODE_NOWAIT;

        filp->f_mapping = handle->bdev->bd_inode->i_mapping;
        filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
        filp->private_data = handle;
        return 0;
}

static int blkdev_release(struct inode *inode, struct file *filp)
{
        bdev_release(filp->private_data);
        return 0;
}

static ssize_t
blkdev_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
        size_t count = iov_iter_count(from);
        ssize_t written;

        written = kiocb_invalidate_pages(iocb, count);
        if (written) {
                if (written == -EBUSY)
                        return 0;
                return written;
        }

        written = blkdev_direct_IO(iocb, from);
        if (written > 0) {
                kiocb_invalidate_post_direct_write(iocb, count);
                iocb->ki_pos += written;
                count -= written;
        }
        if (written != -EIOCBQUEUED)
                iov_iter_revert(from, count - iov_iter_count(from));
        return written;
}

static ssize_t blkdev_buffered_write(struct kiocb *iocb, struct iov_iter *from)
{
        return iomap_file_buffered_write(iocb, from, &blkdev_iomap_ops);
}

/*
 * Write data to the block device.  Only intended for the block device itself
 * and the raw driver which basically is a fake block device.
 *
 * Does not take i_mutex for the write and thus is not for general purpose
 * use.
 */
static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct block_device *bdev = I_BDEV(file->f_mapping->host);
        struct inode *bd_inode = bdev->bd_inode;
        loff_t size = bdev_nr_bytes(bdev);
        size_t shorted = 0;
        ssize_t ret;

        if (bdev_read_only(bdev))
                return -EPERM;

        if (IS_SWAPFILE(bd_inode) && !is_hibernate_resume_dev(bd_inode->i_rdev))
                return -ETXTBSY;

        if (!iov_iter_count(from))
                return 0;

        if (iocb->ki_pos >= size)
                return -ENOSPC;

        if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
                return -EOPNOTSUPP;

        size -= iocb->ki_pos;
        if (iov_iter_count(from) > size) {
                shorted = iov_iter_count(from) - size;
                iov_iter_truncate(from, size);
        }

        ret = file_update_time(file);
        if (ret)
                return ret;

        if (iocb->ki_flags & IOCB_DIRECT) {
                ret = blkdev_direct_write(iocb, from);
                if (ret >= 0 && iov_iter_count(from))
                        ret = direct_write_fallback(iocb, from, ret,
                                        blkdev_buffered_write(iocb, from));
        } else {
                ret = blkdev_buffered_write(iocb, from);
        }

        if (ret > 0)
                ret = generic_write_sync(iocb, ret);
        iov_iter_reexpand(from, iov_iter_count(from) + shorted);
        return ret;
}

static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
        loff_t size = bdev_nr_bytes(bdev);
        loff_t pos = iocb->ki_pos;
        size_t shorted = 0;
        ssize_t ret = 0;
        size_t count;

        if (unlikely(pos + iov_iter_count(to) > size)) {
                if (pos >= size)
                        return 0;
                size -= pos;
                shorted = iov_iter_count(to) - size;
                iov_iter_truncate(to, size);
        }

        count = iov_iter_count(to);
        if (!count)
                goto reexpand; /* skip atime */

        if (iocb->ki_flags & IOCB_DIRECT) {
                ret = kiocb_write_and_wait(iocb, count);
                if (ret < 0)
                        goto reexpand;
                file_accessed(iocb->ki_filp);

                ret = blkdev_direct_IO(iocb, to);
                if (ret >= 0) {
                        iocb->ki_pos += ret;
                        count -= ret;
                }
                iov_iter_revert(to, count - iov_iter_count(to));
                if (ret < 0 || !count)
                        goto reexpand;
        }

        ret = filemap_read(iocb, to, ret);

reexpand:
        if (unlikely(shorted))
                iov_iter_reexpand(to, iov_iter_count(to) + shorted);
        return ret;
}

#define BLKDEV_FALLOC_FL_SUPPORTED                                      \
                (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |           \
                 FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE)

static long blkdev_fallocate(struct file *file, int mode, loff_t start,
                             loff_t len)
{
        struct inode *inode = bdev_file_inode(file);
        struct block_device *bdev = I_BDEV(inode);
        loff_t end = start + len - 1;
        loff_t isize;
        int error;

        /* Fail if we don't recognize the flags. */
        if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED)
                return -EOPNOTSUPP;

        /* Don't go off the end of the device. */
        isize = bdev_nr_bytes(bdev);
        if (start >= isize)
                return -EINVAL;
        if (end >= isize) {
                if (mode & FALLOC_FL_KEEP_SIZE) {
                        len = isize - start;
                        end = start + len - 1;
                } else
                        return -EINVAL;
        }

        /*
         * Don't allow IO that isn't aligned to logical block size.
         */
        if ((start | len) & (bdev_logical_block_size(bdev) - 1))
                return -EINVAL;

        filemap_invalidate_lock(inode->i_mapping);

        /*
         * Invalidate the page cache, including dirty pages, for valid
         * de-allocate mode calls to fallocate().
         */
        switch (mode) {
        case FALLOC_FL_ZERO_RANGE:
        case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
                error = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);
                if (error)
                        goto fail;

                error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
                                             len >> SECTOR_SHIFT, GFP_KERNEL,
                                             BLKDEV_ZERO_NOUNMAP);
                break;
        case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
                error = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);
                if (error)
                        goto fail;

                error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
                                             len >> SECTOR_SHIFT, GFP_KERNEL,
                                             BLKDEV_ZERO_NOFALLBACK);
                break;
        case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
                error = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);
                if (error)
                        goto fail;

                error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
                                             len >> SECTOR_SHIFT, GFP_KERNEL);
                break;
        default:
                error = -EOPNOTSUPP;
        }

 fail:
        filemap_invalidate_unlock(inode->i_mapping);
        return error;
}

static int blkdev_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct inode *bd_inode = bdev_file_inode(file);

        if (bdev_read_only(I_BDEV(bd_inode)))
                return generic_file_readonly_mmap(file, vma);

        return generic_file_mmap(file, vma);
}

const struct file_operations def_blk_fops = {
        .open           = blkdev_open,
        .release        = blkdev_release,
        .llseek         = blkdev_llseek,
        .read_iter      = blkdev_read_iter,
        .write_iter     = blkdev_write_iter,
        .iopoll         = iocb_bio_iopoll,
        .mmap           = blkdev_mmap,
        .fsync          = blkdev_fsync,
        .unlocked_ioctl = blkdev_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = compat_blkdev_ioctl,
#endif
        .splice_read    = filemap_splice_read,
        .splice_write   = iter_file_splice_write,
        .fallocate      = blkdev_fallocate,
};

static __init int blkdev_init(void)
{
        return bioset_init(&blkdev_dio_pool, 4,
                                offsetof(struct blkdev_dio, bio),
                                BIOSET_NEED_BVECS|BIOSET_PERCPU_CACHE);
}
module_init(blkdev_init);