// 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/iomap.h>
#include <linux/backing-dev.h>
#include <linux/uio.h>
#include <linux/task_io_accounting_ops.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;
        iomap_dio_end_io_t      *end_io;
        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)
{
        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);
        dio->submit.cookie = submit_bio(bio);
}

static ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
        struct kiocb *iocb = dio->iocb;
        struct inode *inode = file_inode(iocb->ki_filp);
        loff_t offset = iocb->ki_pos;
        ssize_t ret;

        if (dio->end_io) {
                ret = dio->end_io(iocb,
                                dio->error ? dio->error : dio->size,
                                dio->flags);
        } else {
                ret = dio->error;
        }

        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 dio->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->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);
        }

        /*
         * 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);

        inode_dio_end(file_inode(iocb->ki_filp));
        kfree(dio);

        return ret;
}

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 page *page = ZERO_PAGE(0);
        int flags = REQ_SYNC | REQ_IDLE;
        struct bio *bio;

        bio = bio_alloc(GFP_KERNEL, 1);
        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);
}

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

        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;
        }

        /*
         * Operate on a partial iter trimmed to the extent we were called for.
         * We'll update the iter in the dio once we're done with this extent.
         */
        iter = *dio->submit.iter;
        iov_iter_truncate(&iter, length);

        nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
        if (nr_pages <= 0)
                return 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);
                        return 0;
                }

                bio = bio_alloc(GFP_KERNEL, nr_pages);
                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, &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);
                }

                iov_iter_advance(dio->submit.iter, n);

                dio->size += n;
                pos += n;
                copied += n;

                nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
                iomap_dio_submit_bio(dio, iomap, bio);
        } 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);
        }
        return copied ? copied : 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_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);
        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.
 */
ssize_t
iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
                const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
{
        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, start = pos;
        loff_t end = iocb->ki_pos + count - 1, ret = 0;
        unsigned int flags = IOMAP_DIRECT;
        bool wait_for_completion = is_sync_kiocb(iocb);
        struct blk_plug plug;
        struct iomap_dio *dio;

        lockdep_assert_held(&inode->i_rwsem);

        if (!count)
                return 0;

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

        dio->iocb = iocb;
        atomic_set(&dio->ref, 1);
        dio->size = 0;
        dio->i_size = i_size_read(inode);
        dio->end_io = end_io;
        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) && iov_iter_rw(iter) == READ)
                        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, start, end)) {
                        ret = -EAGAIN;
                        goto out_free_dio;
                }
                flags |= IOMAP_NOWAIT;
        }

        ret = filemap_write_and_wait_range(mapping, start, end);
        if (ret)
                goto out_free_dio;

        /*
         * Try to invalidate cache pages for the range we're direct
         * writing.  If this invalidation fails, tough, the write will
         * still work, but racing two incompatible write paths is a
         * pretty crazy thing to do, so we don't support it 100%.
         */
        ret = invalidate_inode_pages2_range(mapping,
                        start >> PAGE_SHIFT, end >> PAGE_SHIFT);
        if (ret)
                dio_warn_stale_pagecache(iocb->ki_filp);
        ret = 0;

        if (iov_iter_rw(iter) == WRITE && !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)
                        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 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 -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))
                                io_schedule();
                }
                __set_current_state(TASK_RUNNING);
        }

        return iomap_dio_complete(dio);

out_free_dio:
        kfree(dio);
        return ret;
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);