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Message-Id: <1156374495.30517.5.camel@dyn9047017100.beaverton.ibm.com>
Date: Wed, 23 Aug 2006 16:08:15 -0700
From: Badari Pulavarty <pbadari@...ibm.com>
To: Herbert Xu <herbert@...dor.apana.org.au>, akpm@...l.org
Cc: lkml <linux-kernel@...r.kernel.org>,
ext2-devel <Ext2-devel@...ts.sourceforge.net>
Subject: [RFC][PATCH] Manage jbd allocations from its own slabs
Hi,
Here is the fix to "bh: Ensure bh fits within a page" problem
caused by JBD.
BTW, I realized that this problem can happen only with 1k, 2k
filesystems - as 4k, 8k allocations disable slab debug
automatically. But for completeness, I created slabs for those
also.
What do you think ? I ran basic tests and things are fine.
Thanks,
Badari
JBD currently allocates commit and frozen buffers from slabs.
With CONFIG_SLAB_DEBUG, its possible for an allocation to
cross the page boundary causing IO problems.
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=200127
So, instead of allocating these from regular slabs - manage
allocation from its own slabs and disable slab debug for these slabs.
Signed-off-by: Badari Pulavarty <pbadari@...ibm.com>
---
fs/jbd/commit.c | 6 +--
fs/jbd/journal.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++---
fs/jbd/transaction.c | 9 ++---
include/linux/jbd.h | 3 +
4 files changed, 95 insertions(+), 11 deletions(-)
Index: linux-2.6.18-rc4/fs/jbd/journal.c
===================================================================
--- linux-2.6.18-rc4.orig/fs/jbd/journal.c 2006-08-23 14:47:25.000000000 -0700
+++ linux-2.6.18-rc4/fs/jbd/journal.c 2006-08-23 15:59:06.000000000 -0700
@@ -328,10 +328,10 @@
char *tmp;
jbd_unlock_bh_state(bh_in);
- tmp = jbd_rep_kmalloc(bh_in->b_size, GFP_NOFS);
+ tmp = jbd_slab_alloc(bh_in->b_size, GFP_NOFS);
jbd_lock_bh_state(bh_in);
if (jh_in->b_frozen_data) {
- kfree(tmp);
+ jbd_slab_free(tmp, bh_in->b_size);
goto repeat;
}
@@ -1612,6 +1612,89 @@
}
/*
+ * jbd slab management: create 1k, 2k, 4k, 8k slabs and allocate
+ * frozen and commit buffers from these slabs.
+ *
+ * Reason for doing this is to avoid, SLAB_DEBUG - since it could
+ * cause bh to cross page boundary.
+ */
+
+static kmem_cache_t *jbd_slab[4];
+static const char *jbd_slab_names[4] = {
+ "jbd_1k",
+ "jbd_2k",
+ "jbd_4k",
+ "jbd_8k",
+};
+
+static void journal_destroy_jbd_slabs(void)
+{
+ int i;
+
+ for (i=0; i<4; i++) {
+ if (jbd_slab[i])
+ kmem_cache_destroy(jbd_slab[i]);
+ jbd_slab[i] = NULL;
+ }
+}
+
+static int journal_init_jbd_slabs(void)
+{
+ int i = 0;
+ int retval = 0;
+
+ for (i=0; i<4; i++) {
+ unsigned long slab_size = 1024 << i;
+ jbd_slab[i] = kmem_cache_create(jbd_slab_names[i],
+ slab_size, slab_size,
+ 0, NULL, NULL);
+ if (jbd_slab[i] == 0) {
+ journal_destroy_jbd_slabs();
+ retval = -ENOMEM;
+ printk(KERN_EMERG "JBD: no memory for jbd_slab cache\n");
+ goto out;
+ }
+ }
+out:
+ return retval;
+}
+
+static int jbd_find_slab_index(size_t size)
+{
+ int idx = 0;
+
+ switch (size) {
+ case 1024: idx = 0;
+ break;
+ case 2048: idx = 1;
+ break;
+ case 4096: idx = 2;
+ break;
+ case 8192: idx = 3;
+ break;
+ default: printk("JBD unknown slab size %ld\n", size);
+ BUG();
+ }
+ return idx;
+}
+
+void * jbd_slab_alloc(size_t size, gfp_t flags)
+{
+ int idx;
+
+ idx = jbd_find_slab_index(size);
+ return kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
+}
+
+void jbd_slab_free(void *ptr, size_t size)
+{
+ int idx;
+
+ idx = jbd_find_slab_index(size);
+ kmem_cache_free(jbd_slab[idx], ptr);
+}
+
+/*
* Journal_head storage management
*/
static kmem_cache_t *journal_head_cache;
@@ -1799,13 +1882,13 @@
printk(KERN_WARNING "%s: freeing "
"b_frozen_data\n",
__FUNCTION__);
- kfree(jh->b_frozen_data);
+ jbd_slab_free(jh->b_frozen_data, bh->b_size);
}
if (jh->b_committed_data) {
printk(KERN_WARNING "%s: freeing "
"b_committed_data\n",
__FUNCTION__);
- kfree(jh->b_committed_data);
+ jbd_slab_free(jh->b_committed_data, bh->b_size);
}
bh->b_private = NULL;
jh->b_bh = NULL; /* debug, really */
@@ -1953,6 +2036,8 @@
ret = journal_init_journal_head_cache();
if (ret == 0)
ret = journal_init_handle_cache();
+ if (ret == 0)
+ ret = journal_init_jbd_slabs();
return ret;
}
@@ -1961,6 +2046,7 @@
journal_destroy_revoke_caches();
journal_destroy_journal_head_cache();
journal_destroy_handle_cache();
+ journal_destroy_jbd_slabs();
}
static int __init journal_init(void)
Index: linux-2.6.18-rc4/fs/jbd/transaction.c
===================================================================
--- linux-2.6.18-rc4.orig/fs/jbd/transaction.c 2006-08-23 14:05:57.000000000 -0700
+++ linux-2.6.18-rc4/fs/jbd/transaction.c 2006-08-23 14:50:17.000000000 -0700
@@ -666,8 +666,9 @@
if (!frozen_buffer) {
JBUFFER_TRACE(jh, "allocate memory for buffer");
jbd_unlock_bh_state(bh);
- frozen_buffer = jbd_kmalloc(jh2bh(jh)->b_size,
- GFP_NOFS);
+ frozen_buffer =
+ jbd_slab_alloc(jh2bh(jh)->b_size,
+ GFP_NOFS);
if (!frozen_buffer) {
printk(KERN_EMERG
"%s: OOM for frozen_buffer\n",
@@ -879,7 +880,7 @@
repeat:
if (!jh->b_committed_data) {
- committed_data = jbd_kmalloc(jh2bh(jh)->b_size, GFP_NOFS);
+ committed_data = jbd_slab_alloc(jh2bh(jh)->b_size, GFP_NOFS);
if (!committed_data) {
printk(KERN_EMERG "%s: No memory for committed data\n",
__FUNCTION__);
@@ -906,7 +907,7 @@
out:
journal_put_journal_head(jh);
if (unlikely(committed_data))
- kfree(committed_data);
+ jbd_slab_free(committed_data, bh->b_size);
return err;
}
Index: linux-2.6.18-rc4/fs/jbd/commit.c
===================================================================
--- linux-2.6.18-rc4.orig/fs/jbd/commit.c 2006-08-23 14:05:57.000000000 -0700
+++ linux-2.6.18-rc4/fs/jbd/commit.c 2006-08-23 14:50:17.000000000 -0700
@@ -261,7 +261,7 @@
struct buffer_head *bh = jh2bh(jh);
jbd_lock_bh_state(bh);
- kfree(jh->b_committed_data);
+ jbd_slab_free(jh->b_committed_data, bh->b_size);
jh->b_committed_data = NULL;
jbd_unlock_bh_state(bh);
}
@@ -745,14 +745,14 @@
* Otherwise, we can just throw away the frozen data now.
*/
if (jh->b_committed_data) {
- kfree(jh->b_committed_data);
+ jbd_slab_free(jh->b_committed_data, bh->b_size);
jh->b_committed_data = NULL;
if (jh->b_frozen_data) {
jh->b_committed_data = jh->b_frozen_data;
jh->b_frozen_data = NULL;
}
} else if (jh->b_frozen_data) {
- kfree(jh->b_frozen_data);
+ jbd_slab_free(jh->b_frozen_data, bh->b_size);
jh->b_frozen_data = NULL;
}
Index: linux-2.6.18-rc4/include/linux/jbd.h
===================================================================
--- linux-2.6.18-rc4.orig/include/linux/jbd.h 2006-08-23 14:05:57.000000000 -0700
+++ linux-2.6.18-rc4/include/linux/jbd.h 2006-08-23 14:50:17.000000000 -0700
@@ -72,6 +72,9 @@
#endif
extern void * __jbd_kmalloc (const char *where, size_t size, gfp_t flags, int retry);
+extern void * jbd_slab_alloc(size_t size, gfp_t flags);
+extern void jbd_slab_free(void *ptr, size_t size);
+
#define jbd_kmalloc(size, flags) \
__jbd_kmalloc(__FUNCTION__, (size), (flags), journal_oom_retry)
#define jbd_rep_kmalloc(size, flags) \
-
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