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Commit 1fdca9c2 authored by Dave Chinner's avatar Dave Chinner Committed by Dave Chinner
Browse files

xfs: move DIO mapping size calculation 



The mapping size calculation is done last in __xfs_get_blocks(), but
we are going to need the actual mapping size we will use to map the
direct IO correctly in xfs_map_direct(). Factor out the calculation
for code clarity, and move the call to be the first operation in
mapping the extent to the returned buffer.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent a719370b

fs/xfs/xfs_aops.c

+46 −33
Original line number Diff line number Diff line
@@ -1249,6 +1249,47 @@ xfs_map_direct( 
	}

}





/*

 * If this is O_DIRECT or the mpage code calling tell them how large the mapping

 * is, so that we can avoid repeated get_blocks calls.

 *

 * If the mapping spans EOF, then we have to break the mapping up as the mapping

 * for blocks beyond EOF must be marked new so that sub block regions can be

 * correctly zeroed. We can't do this for mappings within EOF unless the mapping

 * was just allocated or is unwritten, otherwise the callers would overwrite

 * existing data with zeros. Hence we have to split the mapping into a range up

 * to and including EOF, and a second mapping for beyond EOF.

 */

static void

xfs_map_trim_size(

	struct inode		*inode,

	sector_t		iblock,

	struct buffer_head	*bh_result,

	struct xfs_bmbt_irec	*imap,

	xfs_off_t		offset,

	ssize_t			size)

{

	xfs_off_t		mapping_size;



	mapping_size = imap->br_startoff + imap->br_blockcount - iblock;

	mapping_size <<= inode->i_blkbits;



	ASSERT(mapping_size > 0);

	if (mapping_size > size)

		mapping_size = size;

	if (offset < i_size_read(inode) &&

	    offset + mapping_size >= i_size_read(inode)) {

		/* limit mapping to block that spans EOF */

		mapping_size = roundup_64(i_size_read(inode) - offset,

					  1 << inode->i_blkbits);

	}

	if (mapping_size > LONG_MAX)

		mapping_size = LONG_MAX;



	bh_result->b_size = mapping_size;

}



STATIC int

__xfs_get_blocks(

	struct inode		*inode,
@@ -1347,6 +1388,11 @@ __xfs_get_blocks( 
		goto out_unlock;

	}



	/* trim mapping down to size requested */

	if (direct || size > (1 << inode->i_blkbits))

		xfs_map_trim_size(inode, iblock, bh_result,

				  &imap, offset, size);



	/*

	 * For unwritten extents do not report a disk address in the buffered

	 * read case (treat as if we're reading into a hole).
@@ -1392,39 +1438,6 @@ __xfs_get_blocks( 
		}

	}



	/*

	 * If this is O_DIRECT or the mpage code calling tell them how large

	 * the mapping is, so that we can avoid repeated get_blocks calls.

	 *

	 * If the mapping spans EOF, then we have to break the mapping up as the

	 * mapping for blocks beyond EOF must be marked new so that sub block

	 * regions can be correctly zeroed. We can't do this for mappings within

	 * EOF unless the mapping was just allocated or is unwritten, otherwise

	 * the callers would overwrite existing data with zeros. Hence we have

	 * to split the mapping into a range up to and including EOF, and a

	 * second mapping for beyond EOF.

	 */

	if (direct || size > (1 << inode->i_blkbits)) {

		xfs_off_t		mapping_size;



		mapping_size = imap.br_startoff + imap.br_blockcount - iblock;

		mapping_size <<= inode->i_blkbits;



		ASSERT(mapping_size > 0);

		if (mapping_size > size)

			mapping_size = size;

		if (offset < i_size_read(inode) &&

		    offset + mapping_size >= i_size_read(inode)) {

			/* limit mapping to block that spans EOF */

			mapping_size = roundup_64(i_size_read(inode) - offset,

						  1 << inode->i_blkbits);

		}

		if (mapping_size > LONG_MAX)

			mapping_size = LONG_MAX;



		bh_result->b_size = mapping_size;

	}



	return 0;



out_unlock: