Re: Deadlocks! help, please!

[Ryusuke Konishi <ryusuke-sG5X7nlA6pw@public.gmane.org>]

Hello, Gábor

On Fri, 2008-01-18 at 19:11 +0900, Ryusuke Konishi wrote:
> Your log actually gave me a great hint!
> 
> The following part of the log indicates that 
> the device mapper faced starvation of a memory pool,

I found another possible cause for the starvation of a memory
pool.  It is not a DM-related problem but a defection of a write
routine of NILFS.
And now I suspect that it's the true cause of your trouble.

Here I attach a test patch to fix the problem.
Could you try the patch ?

The patch can be applied as follows,

 $ cd nilfs-2.0.0-testing-8
 $ patch -p0 < patch_file


So, if rtorrent (or something else) hang again, then
send me a copy of /proc/slabinfo, please.

Thanks in advance,
-- 
Ryusuke Konishi
NILFS team NTT
http://www.nilfs.org/


Index: fs/segbuf.c
===================================================================
--- fs.orig/segbuf.c	2008-01-21 11:01:52.000000000 +0900
+++ fs/segbuf.c	2008-01-21 11:02:38.000000000 +0900
@@ -367,10 +367,10 @@
 {
 	struct bio *bio;
 
-	bio = bio_alloc(GFP_NOIO, nr_vecs);
+	bio = bio_alloc(GFP_NOWAIT, nr_vecs);
 	if (bio == NULL && (current->flags & PF_MEMALLOC)) {
 		while (!bio && (nr_vecs >>= 1))
-			bio = bio_alloc(GFP_NOIO, nr_vecs);
+			bio = bio_alloc(GFP_NOWAIT, nr_vecs);
 	}
 	if (likely(bio)) {
 		bio->bi_bdev = sb->s_bdev;
Index: fs/kern_feature.h
===================================================================
--- fs.orig/kern_feature.h	2008-01-21 11:02:02.000000000 +0900
+++ fs/kern_feature.h	2008-01-21 11:09:33.000000000 +0900
@@ -339,6 +339,13 @@
 	(LINUX_VERSION_CODE < KERNEL_VERSION(2,6,17))
 #endif
 /*
+ * GFP_NOWAIT flag was introduced at linux-2.6.17
+ */
+#ifndef NEED_GFP_NOWAIT
+# define NEED_GFP_NOWAIT	\
+	(LINUX_VERSION_CODE < KERNEL_VERSION(2,6,17))
+#endif
+/*
  * mutex replaced semaphore since linux-2.6.16
  */
 #ifndef NEED_INODE_SEMAPHORE
@@ -440,6 +447,10 @@
 #define GFP_T gfp_t
 #endif
 
+#if NEED_GFP_NOWAIT
+#define GFP_NOWAIT (GFP_ATOMIC & ~__GFP_HIGH)
+#endif
+
 #if NEED_KMEM_CACHE_S
 #define kmem_cache kmem_cache_s
 #endif