[PATCH] Manage jbd allocations from its own slabs

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.

[akpm@osdl.org: cleanups]
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 86 insertions, 6 deletions

diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 8c9b28dff119..f66724ce443a 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -84,6 +84,7 @@ EXPORT_SYMBOL(journal_force_commit);
 
 static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
 static void __journal_abort_soft (journal_t *journal, int errno);
+static int journal_create_jbd_slab(size_t slab_size);
 
 /*
  * Helper function used to manage commit timeouts
@@ -328,10 +329,10 @@ repeat:
                 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;
                 }
 
@@ -1069,17 +1070,17 @@ static int load_superblock(journal_t *journal)
 int journal_load(journal_t *journal)
 {
         int err;
+        journal_superblock_t *sb;
 
         err = load_superblock(journal);
         if (err)
                 return err;
 
+        sb = journal->j_superblock;
         /* If this is a V2 superblock, then we have to check the
          * features flags on it. */
 
         if (journal->j_format_version >= 2) {
-                journal_superblock_t *sb = journal->j_superblock;
-
                 if ((sb->s_feature_ro_compat &
                      ~cpu_to_be32(JFS_KNOWN_ROCOMPAT_FEATURES)) ||
                     (sb->s_feature_incompat &
@@ -1090,6 +1091,13 @@ int journal_load(journal_t *journal)
                 }
         }
 
+        /*
+         * Create a slab for this blocksize
+         */
+        err = journal_create_jbd_slab(cpu_to_be32(sb->s_blocksize));
+        if (err)
+                return err;
+
         /* Let the recovery code check whether it needs to recover any
          * data from the journal. */
         if (journal_recover(journal))
@@ -1612,6 +1620,77 @@ void * __jbd_kmalloc (const char *where, size_t size, gfp_t flags, int retry)
 }
 
 /*
+ * jbd slab management: create 1k, 2k, 4k, 8k slabs as needed
+ * 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.
+ */
+
+#define JBD_MAX_SLABS 5
+#define JBD_SLAB_INDEX(size)  (size >> 11)
+
+static kmem_cache_t *jbd_slab[JBD_MAX_SLABS];
+static const char *jbd_slab_names[JBD_MAX_SLABS] = {
+        "jbd_1k", "jbd_2k", "jbd_4k", NULL, "jbd_8k"
+};
+
+static void journal_destroy_jbd_slabs(void)
+{
+        int i;
+
+        for (i = 0; i < JBD_MAX_SLABS; i++) {
+                if (jbd_slab[i])
+                        kmem_cache_destroy(jbd_slab[i]);
+                jbd_slab[i] = NULL;
+        }
+}
+
+static int journal_create_jbd_slab(size_t slab_size)
+{
+        int i = JBD_SLAB_INDEX(slab_size);
+
+        BUG_ON(i >= JBD_MAX_SLABS);
+
+        /*
+         * Check if we already have a slab created for this size
+         */
+        if (jbd_slab[i])
+                return 0;
+
+        /*
+         * Create a slab and force alignment to be same as slabsize -
+         * this will make sure that allocations won't cross the page
+         * boundary.
+         */
+        jbd_slab[i] = kmem_cache_create(jbd_slab_names[i],
+                                slab_size, slab_size, 0, NULL, NULL);
+        if (!jbd_slab[i]) {
+                printk(KERN_EMERG "JBD: no memory for jbd_slab cache\n");
+                return -ENOMEM;
+        }
+        return 0;
+}
+
+void * jbd_slab_alloc(size_t size, gfp_t flags)
+{
+        int idx;
+
+        idx = JBD_SLAB_INDEX(size);
+        BUG_ON(jbd_slab[idx] == NULL);
+        return kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
+}
+
+void jbd_slab_free(void *ptr,  size_t size)
+{
+        int idx;
+
+        idx = JBD_SLAB_INDEX(size);
+        BUG_ON(jbd_slab[idx] == NULL);
+        kmem_cache_free(jbd_slab[idx], ptr);
+}
+
+/*
  * Journal_head storage management
  */
 static kmem_cache_t *journal_head_cache;
@@ -1799,13 +1878,13 @@ static void __journal_remove_journal_head(struct buffer_head *bh)
                                 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 */
@@ -1961,6 +2040,7 @@ static void journal_destroy_caches(void)
         journal_destroy_revoke_caches();
         journal_destroy_journal_head_cache();
         journal_destroy_handle_cache();
+        journal_destroy_jbd_slabs();
 }
 
 static int __init journal_init(void)