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ocfs2: fix write() performance regression

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On file systems which don't support sparse files, Ocfs2_map_page_blocks()
was reading blocks on appending writes. This caused write performance to
suffer dramatically. Fix this by detecting an appending write on a nonsparse
fs and skipping the read.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
This commit is contained in:
Mark Fasheh 2007-11-01 11:37:48 -07:00
parent 9ea2d32f40
commit 4e9563fd55
1 changed files with 22 additions and 0 deletions
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22
fs/ocfs2/aops.c
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@ -728,6 +728,27 @@ static void ocfs2_clear_page_regions(struct page *page,
kunmap_atomic(kaddr, KM_USER0);
}
/*
* Nonsparse file systems fully allocate before we get to the write
* code. This prevents ocfs2_write() from tagging the write as an
* allocating one, which means ocfs2_map_page_blocks() might try to
* read-in the blocks at the tail of our file. Avoid reading them by
* testing i_size against each block offset.
*/
static int ocfs2_should_read_blk(struct inode *inode, struct page *page,
unsigned int block_start)
{
u64 offset = page_offset(page) + block_start;
if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
return 1;
if (i_size_read(inode) > offset)
return 1;
return 0;
}
/*
* Some of this taken from block_prepare_write(). We already have our
* mapping by now though, and the entire write will be allocating or
@ -781,6 +802,7 @@ int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
set_buffer_uptodate(bh);
} else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
!buffer_new(bh) &&
ocfs2_should_read_blk(inode, page, block_start) &&
(block_start < from || block_end > to)) {
ll_rw_block(READ, 1, &bh);
*wait_bh++=bh;