Attachment 315715 Details for Bug 461082 – Upstream patch for this issue

[patch] Upstream patch for this issue

0001-dio-zero-struct-dio-with-kzalloc-instead-of-manuall.patch (text/plain), 2.89 KB, created by Eugene Teo (Security Response) on 2008-09-04 02:43:32 UTC

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Creator: Eugene Teo (Security Response)

Created: 2008-09-04 02:43:32 UTC

Size: 2.89 KB

patch

obsolete

>From 848c4dd5153c7a0de55470ce99a8e13a63b4703f Mon Sep 17 00:00:00 2001
>From: Zach Brown <zach.brown@oracle.com>
>Date: Mon, 20 Aug 2007 17:12:01 -0700
>Subject: [PATCH] dio: zero struct dio with kzalloc instead of manually
>
>This patch uses kzalloc to zero all of struct dio rather than manually
>trying to track which fields we rely on being zero.  It passed aio+dio
>stress testing and some bug regression testing on ext3.
>
>This patch was introduced by Linus in the conversation that lead up to
>Badari's minimal fix to manually zero .map_bh.b_state in commit:
>
>  6a648fa72161d1f6468dabd96c5d3c0db04f598a
>
>It makes the code a bit smaller.  Maybe a couple fewer cachelines to
>load, if we're lucky:
>
>   text    data     bss     dec     hex filename
>3285925  568506 1304616 5159047  4eb887 vmlinux
>3285797  568506 1304616 5158919  4eb807 vmlinux.patched
>
>I was unable to measure a stable difference in the number of cpu cycles
>spent in blockdev_direct_IO() when pushing aio+dio 256K reads at
>~340MB/s.
>
>So the resulting intent of the patch isn't a performance gain but to
>avoid exposing ourselves to the risk of finding another field like
>.map_bh.b_state where we rely on zeroing but don't enforce it in the
>code.
>
>Signed-off-by: Zach Brown <zach.brown@oracle.com>
>Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>---
> fs/direct-io.c |   18 +-----------------
> 1 files changed, 1 insertions(+), 17 deletions(-)
>
>diff --git a/fs/direct-io.c b/fs/direct-io.c
>index 6874785..901dc55 100644
>--- a/fs/direct-io.c
>+++ b/fs/direct-io.c
>@@ -958,36 +958,22 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
> 	ssize_t ret2;
> 	size_t bytes;
> 
>-	dio->bio = NULL;
> 	dio->inode = inode;
> 	dio->rw = rw;
> 	dio->blkbits = blkbits;
> 	dio->blkfactor = inode->i_blkbits - blkbits;
>-	dio->start_zero_done = 0;
>-	dio->size = 0;
> 	dio->block_in_file = offset >> blkbits;
>-	dio->blocks_available = 0;
>-	dio->cur_page = NULL;
> 
>-	dio->boundary = 0;
>-	dio->reap_counter = 0;
> 	dio->get_block = get_block;
> 	dio->end_io = end_io;
>-	dio->map_bh.b_private = NULL;
>-	dio->map_bh.b_state = 0;
> 	dio->final_block_in_bio = -1;
> 	dio->next_block_for_io = -1;
> 
>-	dio->page_errors = 0;
>-	dio->io_error = 0;
>-	dio->result = 0;
> 	dio->iocb = iocb;
> 	dio->i_size = i_size_read(inode);
> 
> 	spin_lock_init(&dio->bio_lock);
> 	dio->refcount = 1;
>-	dio->bio_list = NULL;
>-	dio->waiter = NULL;
> 
> 	/*
> 	 * In case of non-aligned buffers, we may need 2 more
>@@ -995,8 +981,6 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
> 	 */
> 	if (unlikely(dio->blkfactor))
> 		dio->pages_in_io = 2;
>-	else
>-		dio->pages_in_io = 0;
> 
> 	for (seg = 0; seg < nr_segs; seg++) {
> 		user_addr = (unsigned long)iov[seg].iov_base;
>@@ -1184,7 +1168,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
> 		}
> 	}
> 
>-	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
>+	dio = kzalloc(sizeof(*dio), GFP_KERNEL);
> 	retval = -ENOMEM;
> 	if (!dio)
> 		goto out;
>-- 
>1.5.5.1
>

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