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xfs: move DIO mapping size calculation

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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: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Dave Chinner 2015-04-16 21:58:21 +10:00 committed by Dave Chinner
parent a719370be5
commit 1fdca9c211
1 changed files with 46 additions and 33 deletions
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79
fs/xfs/xfs_aops.c
View file

@ -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: