Re: Ext4 tree backports for 2.6.27.13 and 2.6.28.2

[Chuck Ebbert]

On Wed, 11 Feb 2009 13:29:14 +0530
"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote:

> On Sat, Jan 31, 2009 at 12:25:39AM -0500, Theodore Ts'o wrote:
> > I've updated the ext4 backport branches on the ext4 git tree:
> > 
> >    git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
> >    http://git.kernel.org/?p=linux/kernel/git/tytso/ext4.git
> > 
> > The for-stable branch is branched off of 2.6.28.2, and has a candidate
> > set of patches to be included in the next stable release.  The
> > for-stable-2.6.27 branch is branched off of 2.6.27.13.  
> > 
> > I'm more confident with the 2.6.28 stable candidate than the 2.6.27
> > stable candidates at the moment, but given that we just missed the
> > 2.6.27.14 and 2.6.28.3 release cycles, that should give us plenty of
> > time to test the patches.
> > 
> > 						- Ted
> > 
> > 
> > 8556e8f3 18d5cb0 fd3bd090
> >     ext4: Don't allow new groups to be added during block allocation
> > 
> 
> This commit on for-stable-2.6.27 is not complete.
> ac->alloc_semp is not assigned in the code.
> 

I think this fixes that one:


Add missing pieces to the below patch in the 2.6.27 ext4 patchset.
http://git.kernel.org/?p=linux/kernel/git/tytso/ext4.git;a=commitdiff;h=fd3bd090d7cc93292d3fa361b9c323752417bd7b
"ext4: Don't allow new groups to be added during block allocation"

Signed-off-by: Chuck Ebbert <cebbert@xxxxxxxxxx>

Index: linux-2.6.27.noarch/fs/ext4/mballoc.c
===================================================================
--- linux-2.6.27.noarch.orig/fs/ext4/mballoc.c
+++ linux-2.6.27.noarch/fs/ext4/mballoc.c
@@ -1055,7 +1055,8 @@ static void ext4_mb_release_desc(struct 
 	if (e4b->bd_buddy_page)
 		page_cache_release(e4b->bd_buddy_page);
 	/* Done with the buddy cache */
-	up_read(e4b->alloc_semp);
+	if (e4b->alloc_semp)
+		up_read(e4b->alloc_semp);
 }
 
 
@@ -1375,6 +1376,9 @@ static void ext4_mb_use_best_found(struc
 	get_page(ac->ac_bitmap_page);
 	ac->ac_buddy_page = e4b->bd_buddy_page;
 	get_page(ac->ac_buddy_page);
+	/* on allocation we use ac to track the held semaphore */
+	ac->alloc_semp =  e4b->alloc_semp;
+	e4b->alloc_semp = NULL;
 	/* store last allocated for subsequent stream allocation */
 	if ((ac->ac_flags & EXT4_MB_HINT_DATA)) {
 		spin_lock(&sbi->s_md_lock);
--
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