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Commit 16432985 authored by Chris Mason's avatar Chris Mason
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Btrfs: Add O_DIRECT read and write (writes == buffered + cache flush) 



This adds basic O_DIRECT read and write support.  In the write case, we
just do a normal buffered write followed by a cache flush.  O_DIRECT +
O_SYNC are required to trigger metadata syncs.

In the read case, there is a basic btrfs_get_block call for use by
the generic O_DIRECT code.  This does honor multi-volume mapping rules
but it skips all checksumming.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 85d824c4

fs/btrfs/file.c

+9 −2
Original line number Diff line number Diff line
@@ -796,8 +796,6 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf, 
		     PAGE_CACHE_SIZE / (sizeof(struct page *)));

	pinned[0] = NULL;

	pinned[1] = NULL;

	if (file->f_flags & O_DIRECT)

		return -EINVAL;



	pos = *ppos;

	start_pos = pos;
@@ -909,6 +907,15 @@ out_nolock: 
				      start_pos, num_written);

		if (err < 0)

			num_written = err;

	} else if (num_written > 0 && (file->f_flags & O_DIRECT)) {

		do_sync_mapping_range(inode->i_mapping, start_pos,

				      start_pos + num_written - 1,

				      SYNC_FILE_RANGE_WRITE |

				      SYNC_FILE_RANGE_WAIT_AFTER);



		invalidate_mapping_pages(inode->i_mapping,

		      start_pos >> PAGE_CACHE_SHIFT,

		     (start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);

	}

	current->backing_dev_info = NULL;

	return num_written ? num_written : err;

fs/btrfs/inode.c

+66 −0
Original line number Diff line number Diff line
@@ -2265,6 +2265,70 @@ out: 
	return em;

}



static int btrfs_get_block(struct inode *inode, sector_t iblock,

			struct buffer_head *bh_result, int create)

{

	struct extent_map *em;

	u64 start = (u64)iblock << inode->i_blkbits;

	struct btrfs_multi_bio *multi = NULL;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	u64 len;

	u64 logical;

	u64 map_length;

	int ret = 0;



	em = btrfs_get_extent(inode, NULL, 0, start, bh_result->b_size, 0);



	if (!em || IS_ERR(em))

		goto out;



	if (em->start > start || em->start + em->len <= start)

	    goto out;



	if (em->block_start == EXTENT_MAP_INLINE) {

		ret = -EINVAL;

		goto out;

	}



	if (em->block_start == EXTENT_MAP_HOLE ||

	    em->block_start == EXTENT_MAP_DELALLOC) {

		goto out;

	}



	len = em->start + em->len - start;

	len = min_t(u64, len, INT_LIMIT(typeof(bh_result->b_size)));



	logical = start - em->start;

	logical = em->block_start + logical;



	map_length = len;

	ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,

			      logical, &map_length, &multi, 0);

	BUG_ON(ret);

	bh_result->b_blocknr = multi->stripes[0].physical >> inode->i_blkbits;

	bh_result->b_size = min(map_length, len);

	bh_result->b_bdev = multi->stripes[0].dev->bdev;

	set_buffer_mapped(bh_result);

	kfree(multi);

out:

	free_extent_map(em);

	return ret;

}



static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,

			const struct iovec *iov, loff_t offset,

			unsigned long nr_segs)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;



	if (rw == WRITE)

		return -EINVAL;



	return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,

				  offset, nr_segs, btrfs_get_block, NULL);

}



static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)

{

	return extent_bmap(mapping, iblock, btrfs_get_extent);
@@ -3136,6 +3200,7 @@ out_fail: 
	btrfs_throttle(root);

	return err;

}



static int btrfs_permission(struct inode *inode, int mask,

			    struct nameidata *nd)

{
@@ -3193,6 +3258,7 @@ static struct address_space_operations btrfs_aops = { 
	.readpages	= btrfs_readpages,

	.sync_page	= block_sync_page,

	.bmap		= btrfs_bmap,

	.direct_IO	= btrfs_direct_IO,

	.invalidatepage = btrfs_invalidatepage,

	.releasepage	= btrfs_releasepage,

	.set_page_dirty	= __set_page_dirty_nobuffers,