Release 4.10 fs/iomap.c

/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (c) 2016 Christoph Hellwig.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/dax.h>
#include "internal.h"

/*
 * Execute a iomap write on a segment of the mapping that spans a
 * contiguous range of pages that have identical block mapping state.
 *
 * This avoids the need to map pages individually, do individual allocations
 * for each page and most importantly avoid the need for filesystem specific
 * locking per page. Instead, all the operations are amortised over the entire
 * range of pages. It is assumed that the filesystems will lock whatever
 * resources they require in the iomap_begin call, and release them in the
 * iomap_end call.
 */

loff_t

iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
		struct iomap_ops *ops, void *data, iomap_actor_t actor)
{
	struct iomap iomap = { 0 };
	loff_t written = 0, ret;

	/*
         * Need to map a range from start position for length bytes. This can
         * span multiple pages - it is only guaranteed to return a range of a
         * single type of pages (e.g. all into a hole, all mapped or all
         * unwritten). Failure at this point has nothing to undo.
         *
         * If allocation is required for this range, reserve the space now so
         * that the allocation is guaranteed to succeed later on. Once we copy
         * the data into the page cache pages, then we cannot fail otherwise we
         * expose transient stale data. If the reserve fails, we can safely
         * back out at this point as there is nothing to undo.
         */
	ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
	if (ret)
		return ret;
	if (WARN_ON(iomap.offset > pos))
		return -EIO;

	/*
         * Cut down the length to the one actually provided by the filesystem,
         * as it might not be able to give us the whole size that we requested.
         */
	if (iomap.offset + iomap.length < pos + length)
		length = iomap.offset + iomap.length - pos;

	/*
         * Now that we have guaranteed that the space allocation will succeed.
         * we can do the copy-in page by page without having to worry about
         * failures exposing transient data.
         */
	written = actor(inode, pos, length, data, &iomap);

	/*
         * Now the data has been copied, commit the range we've copied.  This
         * should not fail unless the filesystem has had a fatal error.
         */
	if (ops->iomap_end) {
		ret = ops->iomap_end(inode, pos, length,
				     written > 0 ? written : 0,
				     flags, &iomap);
	}

	return written ? written : ret;
}

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static void

iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
	loff_t i_size = i_size_read(inode);

	/*
         * Only truncate newly allocated pages beyoned EOF, even if the
         * write started inside the existing inode size.
         */
	if (pos + len > i_size)
		truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}

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static int

iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
		struct page **pagep, struct iomap *iomap)
{
	pgoff_t index = pos >> PAGE_SHIFT;
	struct page *page;
	int status = 0;

	BUG_ON(pos + len > iomap->offset + iomap->length);

	if (fatal_signal_pending(current))
		return -EINTR;

	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
	if (!page)
		return -ENOMEM;

	status = __block_write_begin_int(page, pos, len, NULL, iomap);
	if (unlikely(status)) {
		unlock_page(page);
		put_page(page);
		page = NULL;

		iomap_write_failed(inode, pos, len);
	}

	*pagep = page;
	return status;
}

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static int

iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
		unsigned copied, struct page *page)
{
	int ret;

	ret = generic_write_end(NULL, inode->i_mapping, pos, len,
			copied, page, NULL);
	if (ret < len)
		iomap_write_failed(inode, pos, len);
	return ret;
}

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static loff_t

iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct iov_iter *i = data;
	long status = 0;
	ssize_t written = 0;
	unsigned int flags = AOP_FLAG_NOFS;

	/*
         * Copies from kernel address space cannot fail (NFSD is a big user).
         */
	if (!iter_is_iovec(i))
		flags |= AOP_FLAG_UNINTERRUPTIBLE;

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */

		offset = (pos & (PAGE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_count(i));
again:
		if (bytes > length)
			bytes = length;

		/*
                 * Bring in the user page that we will copy from _first_.
                 * Otherwise there's a nasty deadlock on copying from the
                 * same page as we're writing to, without it being marked
                 * up-to-date.
                 *
                 * Not only is this an optimisation, but it is also required
                 * to check that the address is actually valid, when atomic
                 * usercopies are used, below.
                 */
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
			status = -EFAULT;
			break;
		}

		status = iomap_write_begin(inode, pos, bytes, flags, &page,
				iomap);
		if (unlikely(status))
			break;

		if (mapping_writably_mapped(inode->i_mapping))
			flush_dcache_page(page);

		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);

		flush_dcache_page(page);

		status = iomap_write_end(inode, pos, bytes, copied, page);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

		iov_iter_advance(i, copied);
		if (unlikely(copied == 0)) {
			/*
                         * If we were unable to copy any data at all, we must
                         * fall back to a single segment length write.
                         *
                         * If we didn't fallback here, we could livelock
                         * because not all segments in the iov can be copied at
                         * once without a pagefault.
                         */
			bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;
		length -= copied;

		balance_dirty_pages_ratelimited(inode->i_mapping);
	} while (iov_iter_count(i) && length);

	return written ? written : status;
}

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ssize_t

iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
		struct iomap_ops *ops)
{
	struct inode *inode = iocb->ki_filp->f_mapping->host;
	loff_t pos = iocb->ki_pos, ret = 0, written = 0;

	while (iov_iter_count(iter)) {
		ret = iomap_apply(inode, pos, iov_iter_count(iter),
				IOMAP_WRITE, ops, iter, iomap_write_actor);
		if (ret <= 0)
			break;
		pos += ret;
		written += ret;
	}

	return written ? written : ret;
}
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EXPORT_SYMBOL_GPL(iomap_file_buffered_write);


static struct page *

__iomap_read_page(struct inode *inode, loff_t offset)
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;

	page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
	if (IS_ERR(page))
		return page;
	if (!PageUptodate(page)) {
		put_page(page);
		return ERR_PTR(-EIO);
	}
	return page;
}

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static loff_t

iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	long status = 0;
	ssize_t written = 0;

	do {
		struct page *page, *rpage;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */

		offset = (pos & (PAGE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_SIZE - offset, length);

		rpage = __iomap_read_page(inode, pos);
		if (IS_ERR(rpage))
			return PTR_ERR(rpage);

		status = iomap_write_begin(inode, pos, bytes,
				AOP_FLAG_NOFS | AOP_FLAG_UNINTERRUPTIBLE,
				&page, iomap);
		put_page(rpage);
		if (unlikely(status))
			return status;

		WARN_ON_ONCE(!PageUptodate(page));

		status = iomap_write_end(inode, pos, bytes, bytes, page);
		if (unlikely(status <= 0)) {
			if (WARN_ON_ONCE(status == 0))
				return -EIO;
			return status;
		}

		cond_resched();

		pos += status;
		written += status;
		length -= status;

		balance_dirty_pages_ratelimited(inode->i_mapping);
	} while (length);

	return written;
}

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int

iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
		struct iomap_ops *ops)
{
	loff_t ret;

	while (len) {
		ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
				iomap_dirty_actor);
		if (ret <= 0)
			return ret;
		pos += ret;
		len -= ret;
	}

	return 0;
}
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EXPORT_SYMBOL_GPL(iomap_file_dirty);



static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
		unsigned bytes, struct iomap *iomap)
{
	struct page *page;
	int status;

	status = iomap_write_begin(inode, pos, bytes,
			AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
	if (status)
		return status;

	zero_user(page, offset, bytes);
	mark_page_accessed(page);

	return iomap_write_end(inode, pos, bytes, bytes, page);
}

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static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
		struct iomap *iomap)
{
	sector_t sector = iomap->blkno +
		(((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);

	return __dax_zero_page_range(iomap->bdev, sector, offset, bytes);
}

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static loff_t

iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
		void *data, struct iomap *iomap)
{
	bool *did_zero = data;
	loff_t written = 0;
	int status;

	/* already zeroed?  we're done. */
	if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
	    	return count;

	do {
		unsigned offset, bytes;

		offset = pos & (PAGE_SIZE - 1); /* Within page */
		bytes = min_t(unsigned, PAGE_SIZE - offset, count);

		if (IS_DAX(inode))
			status = iomap_dax_zero(pos, offset, bytes, iomap);
		else
			status = iomap_zero(inode, pos, offset, bytes, iomap);
		if (status < 0)
			return status;

		pos += bytes;
		count -= bytes;
		written += bytes;
		if (did_zero)
			*did_zero = true;
	} while (count > 0);

	return written;
}

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int

iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
		struct iomap_ops *ops)
{
	loff_t ret;

	while (len > 0) {
		ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
				ops, did_zero, iomap_zero_range_actor);
		if (ret <= 0)
			return ret;

		pos += ret;
		len -= ret;
	}

	return 0;
}
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EXPORT_SYMBOL_GPL(iomap_zero_range);


int

iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
		struct iomap_ops *ops)
{
	unsigned blocksize = (1 << inode->i_blkbits);
	unsigned off = pos & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!off)
		return 0;
	return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
}
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EXPORT_SYMBOL_GPL(iomap_truncate_page);


static loff_t

iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
		void *data, struct iomap *iomap)
{
	struct page *page = data;
	int ret;

	ret = __block_write_begin_int(page, pos, length, NULL, iomap);
	if (ret)
		return ret;

	block_commit_write(page, 0, length);
	return length;
}

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int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
		struct iomap_ops *ops)
{
	struct page *page = vmf->page;
	struct inode *inode = file_inode(vma->vm_file);
	unsigned long length;
	loff_t offset, size;
	ssize_t ret;

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
	    (page_offset(page) > size)) {
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_SHIFT) > size)
		length = size & ~PAGE_MASK;
	else
		length = PAGE_SIZE;

	offset = page_offset(page);
	while (length > 0) {
		ret = iomap_apply(inode, offset, length,
				IOMAP_WRITE | IOMAP_FAULT, ops, page,
				iomap_page_mkwrite_actor);
		if (unlikely(ret <= 0))
			goto out_unlock;
		offset += ret;
		length -= ret;
	}

	set_page_dirty(page);
	wait_for_stable_page(page);
	return 0;
out_unlock:
	unlock_page(page);
	return ret;
}
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EXPORT_SYMBOL_GPL(iomap_page_mkwrite);


struct fiemap_ctx {
	
struct fiemap_extent_info *fi;
	
struct iomap prev;
};



static int iomap_to_fiemap(struct fiemap_extent_info *fi,
		struct iomap *iomap, u32 flags)
{
	switch (iomap->type) {
	case IOMAP_HOLE:
		/* skip holes */
		return 0;
	case IOMAP_DELALLOC:
		flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
		break;
	case IOMAP_UNWRITTEN:
		flags |= FIEMAP_EXTENT_UNWRITTEN;
		break;
	case IOMAP_MAPPED:
		break;
	}

	if (iomap->flags & IOMAP_F_MERGED)
		flags |= FIEMAP_EXTENT_MERGED;
	if (iomap->flags & IOMAP_F_SHARED)
		flags |= FIEMAP_EXTENT_SHARED;

	return fiemap_fill_next_extent(fi, iomap->offset,
			iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
			iomap->length, flags);

}

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static loff_t

iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct fiemap_ctx *ctx = data;
	loff_t ret = length;

	if (iomap->type == IOMAP_HOLE)
		return length;

	ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
	ctx->prev = *iomap;
	switch (ret) {
	case 0:		/* success */
		return length;
	case 1:		/* extent array full */
		return 0;
	default:
		return ret;
	}
}

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int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
		loff_t start, loff_t len, struct iomap_ops *ops)
{
	struct fiemap_ctx ctx;
	loff_t ret;

	memset(&ctx, 0, sizeof(ctx));
	ctx.fi = fi;
	ctx.prev.type = IOMAP_HOLE;

	ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
	if (ret)
		return ret;

	if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
		ret = filemap_write_and_wait(inode->i_mapping);
		if (ret)
			return ret;
	}

	while (len > 0) {
		ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx,
				iomap_fiemap_actor);
		/* inode with no (attribute) mapping will give ENOENT */
		if (ret == -ENOENT)
			break;
		if (ret < 0)
			return ret;
		if (ret == 0)
			break;

		start += ret;
		len -= ret;
	}

	if (ctx.prev.type != IOMAP_HOLE) {
		ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
		if (ret < 0)
			return ret;
	}

	return 0;
}
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EXPORT_SYMBOL_GPL(iomap_fiemap);

/*
 * Private flags for iomap_dio, must not overlap with the public ones in
 * iomap.h:
 */

#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;

	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;
	};
};



static ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
	struct kiocb *iocb = dio->iocb;
	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 (iocb->ki_pos + ret > dio->i_size &&
		    !(dio->flags & IOMAP_DIO_WRITE))
			ret = dio->i_size - iocb->ki_pos;
		iocb->ki_pos += ret;
	}

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

	return ret;
}

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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;
	bool is_write = (dio->flags & IOMAP_DIO_WRITE);
	ssize_t ret;

	ret = iomap_dio_complete(dio);
	if (is_write && ret > 0)
		ret = generic_write_sync(iocb, ret);
	iocb->ki_complete(iocb, ret, 0);
}

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/*
 * 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);
}

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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_error)
		iomap_dio_set_error(dio, bio->bi_error);

	if (atomic_dec_and_test(&dio->ref)) {
		if (is_sync_kiocb(dio->iocb)) {
			struct task_struct *waiter = dio->submit.waiter;

			WRITE_ONCE(dio->submit.waiter, NULL);
			wake_up_process(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 {
		struct bio_vec *bvec;
		int i;

		bio_for_each_segment_all(bvec, bio, i)
			put_page(bvec->bv_page);
		bio_put(bio);
	}
}

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static blk_qc_t

iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
		unsigned len)
{
	struct page *page = ZERO_PAGE(0)