Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 850 insertions, 0 deletions

diff --git a/block/fops.c b/block/fops.c
new file mode 100644
index 0000000000..73e4274254
--- /dev/null
+++ b/block/fops.c
@@ -0,0 +1,850 @@
+// 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;
+}
+
+static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
+{
+	return block_write_full_page(page, blkdev_get_block, wbc);
+}
+
+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,
+	.writepage	= blkdev_writepage,
+	.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_page	= generic_error_remove_page,
+	.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;
+}
+
+blk_mode_t file_to_blk_mode(struct file *file)
+{
+	blk_mode_t mode = 0;
+
+	if (file->f_mode & FMODE_READ)
+		mode |= BLK_OPEN_READ;
+	if (file->f_mode & FMODE_WRITE)
+		mode |= BLK_OPEN_WRITE;
+	if (file->private_data)
+		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 block_device *bdev;
+
+	/*
+	 * 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;
+
+	/*
+	 * Use the file private data to store the holder for exclusive openes.
+	 * file_to_blk_mode relies on it being present to set BLK_OPEN_EXCL.
+	 */
+	if (filp->f_flags & O_EXCL)
+		filp->private_data = filp;
+
+	bdev = blkdev_get_by_dev(inode->i_rdev, file_to_blk_mode(filp),
+				 filp->private_data, NULL);
+	if (IS_ERR(bdev))
+		return PTR_ERR(bdev);
+
+	if (bdev_nowait(bdev))
+		filp->f_mode |= FMODE_NOWAIT;
+
+	filp->f_mapping = bdev->bd_inode->i_mapping;
+	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
+	return 0;
+}
+
+static int blkdev_release(struct inode *inode, struct file *filp)
+{
+	blkdev_put(I_BDEV(filp->f_mapping->host), 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);