// SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2010 Red Hat, Inc.
   * Copyright (c) 2016-2018 Christoph Hellwig.
   */
  #include <linux/module.h>
  #include <linux/compiler.h>
  #include <linux/fs.h>

  #include <linux/fscrypt.h>

  #include <linux/iomap.h>
  #include <linux/backing-dev.h>
  #include <linux/uio.h>
  #include <linux/task_io_accounting_ops.h>

  #include "trace.h"

  
  #include "../internal.h"
  
  /*
   * Private flags for iomap_dio, must not overlap with the public ones in
   * iomap.h:
   */
  #define IOMAP_DIO_WRITE_FUA	(1 << 28)
  #define IOMAP_DIO_NEED_SYNC	(1 << 29)
  #define IOMAP_DIO_WRITE		(1 << 30)
  #define IOMAP_DIO_DIRTY		(1 << 31)
  
  struct iomap_dio {
  	struct kiocb		*iocb;

  	const struct iomap_dio_ops *dops;

  	loff_t			i_size;
  	loff_t			size;
  	atomic_t		ref;
  	unsigned		flags;
  	int			error;
  	bool			wait_for_completion;
  
  	union {
  		/* used during submission and for synchronous completion: */
  		struct {
  			struct iov_iter		*iter;
  			struct task_struct	*waiter;
  			struct request_queue	*last_queue;
  			blk_qc_t		cookie;
  		} submit;
  
  		/* used for aio completion: */
  		struct {
  			struct work_struct	work;
  		} aio;
  	};
  };
  
  int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
  {
  	struct request_queue *q = READ_ONCE(kiocb->private);
  
  	if (!q)
  		return 0;
  	return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
  }
  EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
  
  static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,

  		struct bio *bio, loff_t pos)

  {
  	atomic_inc(&dio->ref);
  
  	if (dio->iocb->ki_flags & IOCB_HIPRI)
  		bio_set_polled(bio, dio->iocb);
  
  	dio->submit.last_queue = bdev_get_queue(iomap->bdev);

  	if (dio->dops && dio->dops->submit_io)
  		dio->submit.cookie = dio->dops->submit_io(
  				file_inode(dio->iocb->ki_filp),
  				iomap, bio, pos);
  	else
  		dio->submit.cookie = submit_bio(bio);

  }

  ssize_t iomap_dio_complete(struct iomap_dio *dio)

  {

  	const struct iomap_dio_ops *dops = dio->dops;

  	struct kiocb *iocb = dio->iocb;
  	struct inode *inode = file_inode(iocb->ki_filp);
  	loff_t offset = iocb->ki_pos;

  	ssize_t ret = dio->error;

  	if (dops && dops->end_io)
  		ret = dops->end_io(iocb, dio->size, ret, dio->flags);

  
  	if (likely(!ret)) {
  		ret = dio->size;
  		/* check for short read */
  		if (offset + ret > dio->i_size &&
  		    !(dio->flags & IOMAP_DIO_WRITE))
  			ret = dio->i_size - offset;
  		iocb->ki_pos += ret;
  	}
  
  	/*
  	 * Try again to invalidate clean pages which might have been cached by
  	 * non-direct readahead, or faulted in by get_user_pages() if the source
  	 * of the write was an mmap'ed region of the file we're writing.  Either
  	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
  	 * this invalidation fails, tough, the write still worked...
  	 *

  	 * And this page cache invalidation has to be after ->end_io(), as some
  	 * filesystems convert unwritten extents to real allocations in
  	 * ->end_io() when necessary, otherwise a racing buffer read would cache

  	 * zeros from unwritten extents.
  	 */

  	if (!dio->error && dio->size &&

  	    (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
  		int err;
  		err = invalidate_inode_pages2_range(inode->i_mapping,
  				offset >> PAGE_SHIFT,
  				(offset + dio->size - 1) >> PAGE_SHIFT);
  		if (err)
  			dio_warn_stale_pagecache(iocb->ki_filp);
  	}

  	inode_dio_end(file_inode(iocb->ki_filp));

  	/*
  	 * If this is a DSYNC write, make sure we push it to stable storage now
  	 * that we've written data.
  	 */
  	if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
  		ret = generic_write_sync(iocb, ret);

  	kfree(dio);
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(iomap_dio_complete);

  
  static void iomap_dio_complete_work(struct work_struct *work)
  {
  	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
  	struct kiocb *iocb = dio->iocb;
  
  	iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
  }
  
  /*
   * Set an error in the dio if none is set yet.  We have to use cmpxchg
   * as the submission context and the completion context(s) can race to
   * update the error.
   */
  static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
  {
  	cmpxchg(&dio->error, 0, ret);
  }
  
  static void iomap_dio_bio_end_io(struct bio *bio)
  {
  	struct iomap_dio *dio = bio->bi_private;
  	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
  
  	if (bio->bi_status)
  		iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
  
  	if (atomic_dec_and_test(&dio->ref)) {
  		if (dio->wait_for_completion) {
  			struct task_struct *waiter = dio->submit.waiter;
  			WRITE_ONCE(dio->submit.waiter, NULL);
  			blk_wake_io_task(waiter);
  		} else if (dio->flags & IOMAP_DIO_WRITE) {
  			struct inode *inode = file_inode(dio->iocb->ki_filp);
  
  			INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
  			queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
  		} else {
  			iomap_dio_complete_work(&dio->aio.work);
  		}
  	}
  
  	if (should_dirty) {
  		bio_check_pages_dirty(bio);
  	} else {
  		bio_release_pages(bio, false);
  		bio_put(bio);
  	}
  }
  
  static void
  iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
  		unsigned len)
  {

  	struct inode *inode = file_inode(dio->iocb->ki_filp);

  	struct page *page = ZERO_PAGE(0);
  	int flags = REQ_SYNC | REQ_IDLE;
  	struct bio *bio;
  
  	bio = bio_alloc(GFP_KERNEL, 1);

  	fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
  				  GFP_KERNEL);

  	bio_set_dev(bio, iomap->bdev);
  	bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
  	bio->bi_private = dio;
  	bio->bi_end_io = iomap_dio_bio_end_io;
  
  	get_page(page);
  	__bio_add_page(bio, page, len, 0);
  	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);

  	iomap_dio_submit_bio(dio, iomap, bio, pos);

  }
  
  static loff_t
  iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
  		struct iomap_dio *dio, struct iomap *iomap)
  {
  	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
  	unsigned int fs_block_size = i_blocksize(inode), pad;
  	unsigned int align = iov_iter_alignment(dio->submit.iter);

  	struct bio *bio;
  	bool need_zeroout = false;
  	bool use_fua = false;
  	int nr_pages, ret = 0;
  	size_t copied = 0;

  	size_t orig_count;

  
  	if ((pos | length | align) & ((1 << blkbits) - 1))
  		return -EINVAL;
  
  	if (iomap->type == IOMAP_UNWRITTEN) {
  		dio->flags |= IOMAP_DIO_UNWRITTEN;
  		need_zeroout = true;
  	}
  
  	if (iomap->flags & IOMAP_F_SHARED)
  		dio->flags |= IOMAP_DIO_COW;
  
  	if (iomap->flags & IOMAP_F_NEW) {
  		need_zeroout = true;
  	} else if (iomap->type == IOMAP_MAPPED) {
  		/*
  		 * Use a FUA write if we need datasync semantics, this is a pure
  		 * data IO that doesn't require any metadata updates (including
  		 * after IO completion such as unwritten extent conversion) and
  		 * the underlying device supports FUA. This allows us to avoid
  		 * cache flushes on IO completion.
  		 */
  		if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
  		    (dio->flags & IOMAP_DIO_WRITE_FUA) &&
  		    blk_queue_fua(bdev_get_queue(iomap->bdev)))
  			use_fua = true;
  	}
  
  	/*

  	 * Save the original count and trim the iter to just the extent we
  	 * are operating on right now.  The iter will be re-expanded once
  	 * we are done.

  	 */

  	orig_count = iov_iter_count(dio->submit.iter);
  	iov_iter_truncate(dio->submit.iter, length);

  	nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
  	if (nr_pages <= 0) {
  		ret = nr_pages;
  		goto out;
  	}

  	nr_pages = fscrypt_limit_dio_pages(inode, pos, nr_pages);

  
  	if (need_zeroout) {
  		/* zero out from the start of the block to the write offset */
  		pad = pos & (fs_block_size - 1);
  		if (pad)
  			iomap_dio_zero(dio, iomap, pos - pad, pad);
  	}
  
  	do {
  		size_t n;
  		if (dio->error) {
  			iov_iter_revert(dio->submit.iter, copied);

  			copied = ret = 0;
  			goto out;

  		}
  
  		bio = bio_alloc(GFP_KERNEL, nr_pages);

  		fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
  					  GFP_KERNEL);

  		bio_set_dev(bio, iomap->bdev);
  		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
  		bio->bi_write_hint = dio->iocb->ki_hint;
  		bio->bi_ioprio = dio->iocb->ki_ioprio;
  		bio->bi_private = dio;
  		bio->bi_end_io = iomap_dio_bio_end_io;

  		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);

  		if (unlikely(ret)) {
  			/*
  			 * We have to stop part way through an IO. We must fall
  			 * through to the sub-block tail zeroing here, otherwise
  			 * this short IO may expose stale data in the tail of
  			 * the block we haven't written data to.
  			 */
  			bio_put(bio);
  			goto zero_tail;
  		}
  
  		n = bio->bi_iter.bi_size;
  		if (dio->flags & IOMAP_DIO_WRITE) {
  			bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
  			if (use_fua)
  				bio->bi_opf |= REQ_FUA;
  			else
  				dio->flags &= ~IOMAP_DIO_WRITE_FUA;
  			task_io_account_write(n);
  		} else {
  			bio->bi_opf = REQ_OP_READ;
  			if (dio->flags & IOMAP_DIO_DIRTY)
  				bio_set_pages_dirty(bio);
  		}

  		dio->size += n;

  		copied += n;

  		nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);

  		nr_pages = fscrypt_limit_dio_pages(inode, pos, nr_pages);

  		iomap_dio_submit_bio(dio, iomap, bio, pos);
  		pos += n;

  	} while (nr_pages);
  
  	/*
  	 * We need to zeroout the tail of a sub-block write if the extent type
  	 * requires zeroing or the write extends beyond EOF. If we don't zero
  	 * the block tail in the latter case, we can expose stale data via mmap
  	 * reads of the EOF block.
  	 */
  zero_tail:
  	if (need_zeroout ||
  	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
  		/* zero out from the end of the write to the end of the block */
  		pad = pos & (fs_block_size - 1);
  		if (pad)
  			iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
  	}

  out:
  	/* Undo iter limitation to current extent */
  	iov_iter_reexpand(dio->submit.iter, orig_count - copied);

  	if (copied)
  		return copied;
  	return ret;

  }
  
  static loff_t
  iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
  {
  	length = iov_iter_zero(length, dio->submit.iter);
  	dio->size += length;
  	return length;
  }
  
  static loff_t
  iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
  		struct iomap_dio *dio, struct iomap *iomap)
  {
  	struct iov_iter *iter = dio->submit.iter;
  	size_t copied;
  
  	BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
  
  	if (dio->flags & IOMAP_DIO_WRITE) {
  		loff_t size = inode->i_size;
  
  		if (pos > size)
  			memset(iomap->inline_data + size, 0, pos - size);
  		copied = copy_from_iter(iomap->inline_data + pos, length, iter);
  		if (copied) {
  			if (pos + copied > size)
  				i_size_write(inode, pos + copied);
  			mark_inode_dirty(inode);
  		}
  	} else {
  		copied = copy_to_iter(iomap->inline_data + pos, length, iter);
  	}
  	dio->size += copied;
  	return copied;
  }
  
  static loff_t
  iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,

  		void *data, struct iomap *iomap, struct iomap *srcmap)

  {
  	struct iomap_dio *dio = data;
  
  	switch (iomap->type) {
  	case IOMAP_HOLE:
  		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
  			return -EIO;
  		return iomap_dio_hole_actor(length, dio);
  	case IOMAP_UNWRITTEN:
  		if (!(dio->flags & IOMAP_DIO_WRITE))
  			return iomap_dio_hole_actor(length, dio);
  		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
  	case IOMAP_MAPPED:
  		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
  	case IOMAP_INLINE:
  		return iomap_dio_inline_actor(inode, pos, length, dio, iomap);

  	case IOMAP_DELALLOC:
  		/*
  		 * DIO is not serialised against mmap() access at all, and so
  		 * if the page_mkwrite occurs between the writeback and the
  		 * iomap_apply() call in the DIO path, then it will see the
  		 * DELALLOC block that the page-mkwrite allocated.
  		 */
  		pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s
  ",
  				    dio->iocb->ki_filp, current->comm);
  		return -EIO;

  	default:
  		WARN_ON_ONCE(1);
  		return -EIO;
  	}
  }
  
  /*
   * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
   * is being issued as AIO or not.  This allows us to optimise pure data writes
   * to use REQ_FUA rather than requiring generic_write_sync() to issue a
   * REQ_FLUSH post write. This is slightly tricky because a single request here
   * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
   * may be pure data writes. In that case, we still need to do a full data sync
   * completion.

   *
   * Returns -ENOTBLK In case of a page invalidation invalidation failure for
   * writes.  The callers needs to fall back to buffered I/O in this case.

   */

  struct iomap_dio *
  __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

  		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
  		bool wait_for_completion)

  {
  	struct address_space *mapping = iocb->ki_filp->f_mapping;
  	struct inode *inode = file_inode(iocb->ki_filp);
  	size_t count = iov_iter_count(iter);

  	loff_t pos = iocb->ki_pos;

  	loff_t end = iocb->ki_pos + count - 1, ret = 0;
  	unsigned int flags = IOMAP_DIRECT;

  	struct blk_plug plug;
  	struct iomap_dio *dio;

  	if (!count)

  		return NULL;

  	if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))

  		return ERR_PTR(-EIO);

  	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
  	if (!dio)

  		return ERR_PTR(-ENOMEM);

  
  	dio->iocb = iocb;
  	atomic_set(&dio->ref, 1);
  	dio->size = 0;
  	dio->i_size = i_size_read(inode);

  	dio->dops = dops;

  	dio->error = 0;
  	dio->flags = 0;
  
  	dio->submit.iter = iter;
  	dio->submit.waiter = current;
  	dio->submit.cookie = BLK_QC_T_NONE;
  	dio->submit.last_queue = NULL;
  
  	if (iov_iter_rw(iter) == READ) {
  		if (pos >= dio->i_size)
  			goto out_free_dio;

  		if (iter_is_iovec(iter))

  			dio->flags |= IOMAP_DIO_DIRTY;
  	} else {
  		flags |= IOMAP_WRITE;
  		dio->flags |= IOMAP_DIO_WRITE;
  
  		/* for data sync or sync, we need sync completion processing */
  		if (iocb->ki_flags & IOCB_DSYNC)
  			dio->flags |= IOMAP_DIO_NEED_SYNC;
  
  		/*
  		 * For datasync only writes, we optimistically try using FUA for
  		 * this IO.  Any non-FUA write that occurs will clear this flag,
  		 * hence we know before completion whether a cache flush is
  		 * necessary.
  		 */
  		if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
  			dio->flags |= IOMAP_DIO_WRITE_FUA;
  	}
  
  	if (iocb->ki_flags & IOCB_NOWAIT) {

  		if (filemap_range_has_page(mapping, pos, end)) {

  			ret = -EAGAIN;
  			goto out_free_dio;
  		}
  		flags |= IOMAP_NOWAIT;
  	}

  	ret = filemap_write_and_wait_range(mapping, pos, end);

  	if (ret)
  		goto out_free_dio;

  	if (iov_iter_rw(iter) == WRITE) {
  		/*
  		 * Try to invalidate cache pages for the range we are writing.

  		 * If this invalidation fails, let the caller fall back to
  		 * buffered I/O.

  		 */
  		if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,

  				end >> PAGE_SHIFT)) {
  			trace_iomap_dio_invalidate_fail(inode, pos, count);
  			ret = -ENOTBLK;

  			goto out_free_dio;

  		}

  		if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
  			ret = sb_init_dio_done_wq(inode->i_sb);
  			if (ret < 0)
  				goto out_free_dio;
  		}

  	}
  
  	inode_dio_begin(inode);
  
  	blk_start_plug(&plug);
  	do {
  		ret = iomap_apply(inode, pos, count, flags, ops, dio,
  				iomap_dio_actor);
  		if (ret <= 0) {
  			/* magic error code to fall back to buffered I/O */
  			if (ret == -ENOTBLK) {
  				wait_for_completion = true;
  				ret = 0;
  			}
  			break;
  		}
  		pos += ret;

  		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
  			/*
  			 * We only report that we've read data up to i_size.
  			 * Revert iter to a state corresponding to that as
  			 * some callers (such as splice code) rely on it.
  			 */
  			iov_iter_revert(iter, pos - dio->i_size);

  			break;

  		}

  	} while ((count = iov_iter_count(iter)) > 0);
  	blk_finish_plug(&plug);
  
  	if (ret < 0)
  		iomap_dio_set_error(dio, ret);
  
  	/*
  	 * If all the writes we issued were FUA, we don't need to flush the
  	 * cache on IO completion. Clear the sync flag for this case.
  	 */
  	if (dio->flags & IOMAP_DIO_WRITE_FUA)
  		dio->flags &= ~IOMAP_DIO_NEED_SYNC;
  
  	WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
  	WRITE_ONCE(iocb->private, dio->submit.last_queue);
  
  	/*
  	 * We are about to drop our additional submission reference, which

  	 * might be the last reference to the dio.  There are three different
  	 * ways we can progress here:

  	 *
  	 *  (a) If this is the last reference we will always complete and free
  	 *	the dio ourselves.
  	 *  (b) If this is not the last reference, and we serve an asynchronous
  	 *	iocb, we must never touch the dio after the decrement, the
  	 *	I/O completion handler will complete and free it.
  	 *  (c) If this is not the last reference, but we serve a synchronous
  	 *	iocb, the I/O completion handler will wake us up on the drop
  	 *	of the final reference, and we will complete and free it here
  	 *	after we got woken by the I/O completion handler.
  	 */
  	dio->wait_for_completion = wait_for_completion;
  	if (!atomic_dec_and_test(&dio->ref)) {
  		if (!wait_for_completion)

  			return ERR_PTR(-EIOCBQUEUED);

  
  		for (;;) {
  			set_current_state(TASK_UNINTERRUPTIBLE);
  			if (!READ_ONCE(dio->submit.waiter))
  				break;
  
  			if (!(iocb->ki_flags & IOCB_HIPRI) ||
  			    !dio->submit.last_queue ||
  			    !blk_poll(dio->submit.last_queue,
  					 dio->submit.cookie, true))

  				blk_io_schedule();

  		}
  		__set_current_state(TASK_RUNNING);
  	}

  	return dio;

  
  out_free_dio:
  	kfree(dio);

  	if (ret)
  		return ERR_PTR(ret);
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(__iomap_dio_rw);
  
  ssize_t
  iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
  		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
  		bool wait_for_completion)
  {
  	struct iomap_dio *dio;
  
  	dio = __iomap_dio_rw(iocb, iter, ops, dops, wait_for_completion);
  	if (IS_ERR_OR_NULL(dio))
  		return PTR_ERR_OR_ZERO(dio);
  	return iomap_dio_complete(dio);

  }
  EXPORT_SYMBOL_GPL(iomap_dio_rw);