lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c

Now it's ready to move the mempool based SG chained allocator code from
SCSI driver to lib/sg_pool.c, which will be compiled only based on a Kconfig
symbol CONFIG_SG_POOL.

SCSI selects CONFIG_SG_POOL.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

7 files changed, 206 insertions, 156 deletions

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 0950567e6269..98e5d51a3346 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -17,6 +17,7 @@ config SCSI
         tristate "SCSI device support"
         depends on BLOCK
         select SCSI_DMA if HAS_DMA
+        select SG_POOL
         ---help---
           If you want to use a SCSI hard disk, SCSI tape drive, SCSI CD-ROM or
           any other SCSI device under Linux, say Y and make sure that you know
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8f776f1e95ce..b920c5dabf60 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -14,8 +14,6 @@
 #include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
-#include <linux/mempool.h>
-#include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/pci.h>
 #include <linux/delay.h>
@@ -40,39 +38,6 @@
 #include "scsi_logging.h"
 
 
-#define SG_MEMPOOL_NR           ARRAY_SIZE(sg_pools)
-#define SG_MEMPOOL_SIZE         2
-
-struct sg_pool {
-        size_t          size;
-        char            *name;
-        struct kmem_cache       *slab;
-        mempool_t       *pool;
-};
-
-#define SP(x) { .size = x, "sgpool-" __stringify(x) }
-#if (SG_CHUNK_SIZE < 32)
-#error SG_CHUNK_SIZE is too small (must be 32 or greater)
-#endif
-static struct sg_pool sg_pools[] = {
-        SP(8),
-        SP(16),
-#if (SG_CHUNK_SIZE > 32)
-        SP(32),
-#if (SG_CHUNK_SIZE > 64)
-        SP(64),
-#if (SG_CHUNK_SIZE > 128)
-        SP(128),
-#if (SG_CHUNK_SIZE > 256)
-#error SG_CHUNK_SIZE is too large (256 MAX)
-#endif
-#endif
-#endif
-#endif
-        SP(SG_CHUNK_SIZE)
-};
-#undef SP
-
 struct kmem_cache *scsi_sdb_cache;
 
 /*
@@ -553,65 +518,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
                 scsi_run_queue(sdev->request_queue);
 }
 
-static inline unsigned int sg_pool_index(unsigned short nents)
-{
-        unsigned int index;
-
-        BUG_ON(nents > SG_CHUNK_SIZE);
-
-        if (nents <= 8)
-                index = 0;
-        else
-                index = get_count_order(nents) - 3;
-
-        return index;
-}
-
-static void sg_pool_free(struct scatterlist *sgl, unsigned int nents)
-{
-        struct sg_pool *sgp;
-
-        sgp = sg_pools + sg_pool_index(nents);
-        mempool_free(sgl, sgp->pool);
-}
-
-static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
-{
-        struct sg_pool *sgp;
-
-        sgp = sg_pools + sg_pool_index(nents);
-        return mempool_alloc(sgp->pool, gfp_mask);
-}
-
-static void sg_free_table_chained(struct sg_table *table, bool first_chunk)
-{
-        if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
-                return;
-        __sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
-}
-
-static int sg_alloc_table_chained(struct sg_table *table, int nents,
-                struct scatterlist *first_chunk)
-{
-        int ret;
-
-        BUG_ON(!nents);
-
-        if (first_chunk) {
-                if (nents <= SG_CHUNK_SIZE) {
-                        table->nents = table->orig_nents = nents;
-                        sg_init_table(table->sgl, nents);
-                        return 0;
-                }
-        }
-
-        ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
-                               first_chunk, GFP_ATOMIC, sg_pool_alloc);
-        if (unlikely(ret))
-                sg_free_table_chained(table, (bool)first_chunk);
-        return ret;
-}
-
 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
 {
         if (cmd->request->cmd_type == REQ_TYPE_FS) {
@@ -2269,8 +2175,6 @@ EXPORT_SYMBOL(scsi_unblock_requests);
 
 int __init scsi_init_queue(void)
 {
-        int i;
-
         scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
                                            sizeof(struct scsi_data_buffer),
                                            0, 0, NULL);
@@ -2279,53 +2183,12 @@ int __init scsi_init_queue(void)
                 return -ENOMEM;
         }
 
-        for (i = 0; i < SG_MEMPOOL_NR; i++) {
-                struct sg_pool *sgp = sg_pools + i;
-                int size = sgp->size * sizeof(struct scatterlist);
-
-                sgp->slab = kmem_cache_create(sgp->name, size, 0,
-                                SLAB_HWCACHE_ALIGN, NULL);
-                if (!sgp->slab) {
-                        printk(KERN_ERR "SCSI: can't init sg slab %s\n",
-                                        sgp->name);
-                        goto cleanup_sdb;
-                }
-
-                sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
-                                                     sgp->slab);
-                if (!sgp->pool) {
-                        printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
-                                        sgp->name);
-                        goto cleanup_sdb;
-                }
-        }
-
         return 0;
-
-cleanup_sdb:
-        for (i = 0; i < SG_MEMPOOL_NR; i++) {
-                struct sg_pool *sgp = sg_pools + i;
-                if (sgp->pool)
-                        mempool_destroy(sgp->pool);
-                if (sgp->slab)
-                        kmem_cache_destroy(sgp->slab);
-        }
-        kmem_cache_destroy(scsi_sdb_cache);
-
-        return -ENOMEM;
 }
 
 void scsi_exit_queue(void)
 {
-        int i;
-
         kmem_cache_destroy(scsi_sdb_cache);
-
-        for (i = 0; i < SG_MEMPOOL_NR; i++) {
-                struct sg_pool *sgp = sg_pools + i;
-                mempool_destroy(sgp->pool);
-                kmem_cache_destroy(sgp->slab);
-        }
 }
 
 /**
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 556ec1ea2574..cb3c8fe6acd7 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -286,6 +286,31 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 #define SG_MAX_SINGLE_ALLOC             (PAGE_SIZE / sizeof(struct scatterlist))
 
 /*
+ * The maximum number of SG segments that we will put inside a
+ * scatterlist (unless chaining is used). Should ideally fit inside a
+ * single page, to avoid a higher order allocation.  We could define this
+ * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
+ * minimum value is 32
+ */
+#define SG_CHUNK_SIZE   128
+
+/*
+ * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
+ * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
+ */
+#ifdef CONFIG_ARCH_HAS_SG_CHAIN
+#define SG_MAX_SEGMENTS 2048
+#else
+#define SG_MAX_SEGMENTS SG_CHUNK_SIZE
+#endif
+
+#ifdef CONFIG_SG_POOL
+void sg_free_table_chained(struct sg_table *table, bool first_chunk);
+int sg_alloc_table_chained(struct sg_table *table, int nents,
+                           struct scatterlist *first_chunk);
+#endif
+
+/*
  * sg page iterator
  *
  * Iterates over sg entries page-by-page.  On each successful iteration,
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 74dafa75bae7..8ec7c30e35af 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -18,25 +18,6 @@ enum scsi_timeouts {
 };
 
 /*
- * The maximum number of SG segments that we will put inside a
- * scatterlist (unless chaining is used). Should ideally fit inside a
- * single page, to avoid a higher order allocation.  We could define this
- * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
- * minimum value is 32
- */
-#define SG_CHUNK_SIZE   128
-
-/*
- * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
- * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
- */
-#ifdef CONFIG_ARCH_HAS_SG_CHAIN
-#define SG_MAX_SEGMENTS 2048
-#else
-#define SG_MAX_SEGMENTS SG_CHUNK_SIZE
-#endif
-
-/*
  * DIX-capable adapters effectively support infinite chaining for the
  * protection information scatterlist
  */
diff --git a/lib/Kconfig b/lib/Kconfig
index 3cca1222578e..61d55bd0ed89 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -523,6 +523,13 @@ config SG_SPLIT
          a scatterlist. This should be selected by a driver or an API which
          whishes to split a scatterlist amongst multiple DMA channels.
 
+config SG_POOL
+        def_bool n
+        help
+         Provides a helper to allocate chained scatterlists. This should be
+         selected by a driver or an API which whishes to allocate chained
+         scatterlist.
+
 #
 # sg chaining option
 #
diff --git a/lib/Makefile b/lib/Makefile
index 7bd6fd436c97..bf01c2673423 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -178,6 +178,7 @@ obj-$(CONFIG_GENERIC_STRNLEN_USER) += strnlen_user.o
 obj-$(CONFIG_GENERIC_NET_UTILS) += net_utils.o
 
 obj-$(CONFIG_SG_SPLIT) += sg_split.o
+obj-$(CONFIG_SG_POOL) += sg_pool.o
 obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
 obj-$(CONFIG_IRQ_POLL) += irq_poll.o
 
diff --git a/lib/sg_pool.c b/lib/sg_pool.c
new file mode 100644
index 000000000000..6dd30615a201
--- /dev/null
+++ b/lib/sg_pool.c
@@ -0,0 +1,172 @@
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/mempool.h>
+#include <linux/slab.h>
+
+#define SG_MEMPOOL_NR           ARRAY_SIZE(sg_pools)
+#define SG_MEMPOOL_SIZE         2
+
+struct sg_pool {
+        size_t          size;
+        char            *name;
+        struct kmem_cache       *slab;
+        mempool_t       *pool;
+};
+
+#define SP(x) { .size = x, "sgpool-" __stringify(x) }
+#if (SG_CHUNK_SIZE < 32)
+#error SG_CHUNK_SIZE is too small (must be 32 or greater)
+#endif
+static struct sg_pool sg_pools[] = {
+        SP(8),
+        SP(16),
+#if (SG_CHUNK_SIZE > 32)
+        SP(32),
+#if (SG_CHUNK_SIZE > 64)
+        SP(64),
+#if (SG_CHUNK_SIZE > 128)
+        SP(128),
+#if (SG_CHUNK_SIZE > 256)
+#error SG_CHUNK_SIZE is too large (256 MAX)
+#endif
+#endif
+#endif
+#endif
+        SP(SG_CHUNK_SIZE)
+};
+#undef SP
+
+static inline unsigned int sg_pool_index(unsigned short nents)
+{
+        unsigned int index;
+
+        BUG_ON(nents > SG_CHUNK_SIZE);
+
+        if (nents <= 8)
+                index = 0;
+        else
+                index = get_count_order(nents) - 3;
+
+        return index;
+}
+
+static void sg_pool_free(struct scatterlist *sgl, unsigned int nents)
+{
+        struct sg_pool *sgp;
+
+        sgp = sg_pools + sg_pool_index(nents);
+        mempool_free(sgl, sgp->pool);
+}
+
+static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
+{
+        struct sg_pool *sgp;
+
+        sgp = sg_pools + sg_pool_index(nents);
+        return mempool_alloc(sgp->pool, gfp_mask);
+}
+
+/**
+ * sg_free_table_chained - Free a previously mapped sg table
+ * @table:      The sg table header to use
+ * @first_chunk: was first_chunk not NULL in sg_alloc_table_chained?
+ *
+ *  Description:
+ *    Free an sg table previously allocated and setup with
+ *    sg_alloc_table_chained().
+ *
+ **/
+void sg_free_table_chained(struct sg_table *table, bool first_chunk)
+{
+        if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
+                return;
+        __sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
+}
+EXPORT_SYMBOL_GPL(sg_free_table_chained);
+
+/**
+ * sg_alloc_table_chained - Allocate and chain SGLs in an sg table
+ * @table:      The sg table header to use
+ * @nents:      Number of entries in sg list
+ * @first_chunk: first SGL
+ *
+ *  Description:
+ *    Allocate and chain SGLs in an sg table. If @nents@ is larger than
+ *    SG_CHUNK_SIZE a chained sg table will be setup.
+ *
+ **/
+int sg_alloc_table_chained(struct sg_table *table, int nents,
+                struct scatterlist *first_chunk)
+{
+        int ret;
+
+        BUG_ON(!nents);
+
+        if (first_chunk) {
+                if (nents <= SG_CHUNK_SIZE) {
+                        table->nents = table->orig_nents = nents;
+                        sg_init_table(table->sgl, nents);
+                        return 0;
+                }
+        }
+
+        ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
+                               first_chunk, GFP_ATOMIC, sg_pool_alloc);
+        if (unlikely(ret))
+                sg_free_table_chained(table, (bool)first_chunk);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
+
+static __init int sg_pool_init(void)
+{
+        int i;
+
+        for (i = 0; i < SG_MEMPOOL_NR; i++) {
+                struct sg_pool *sgp = sg_pools + i;
+                int size = sgp->size * sizeof(struct scatterlist);
+
+                sgp->slab = kmem_cache_create(sgp->name, size, 0,
+                                SLAB_HWCACHE_ALIGN, NULL);
+                if (!sgp->slab) {
+                        printk(KERN_ERR "SG_POOL: can't init sg slab %s\n",
+                                        sgp->name);
+                        goto cleanup_sdb;
+                }
+
+                sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
+                                                     sgp->slab);
+                if (!sgp->pool) {
+                        printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n",
+                                        sgp->name);
+                        goto cleanup_sdb;
+                }
+        }
+
+        return 0;
+
+cleanup_sdb:
+        for (i = 0; i < SG_MEMPOOL_NR; i++) {
+                struct sg_pool *sgp = sg_pools + i;
+                if (sgp->pool)
+                        mempool_destroy(sgp->pool);
+                if (sgp->slab)
+                        kmem_cache_destroy(sgp->slab);
+        }
+
+        return -ENOMEM;
+}
+
+static __exit void sg_pool_exit(void)
+{
+        int i;
+
+        for (i = 0; i < SG_MEMPOOL_NR; i++) {
+                struct sg_pool *sgp = sg_pools + i;
+                mempool_destroy(sgp->pool);
+                kmem_cache_destroy(sgp->slab);
+        }
+}
+
+module_init(sg_pool_init);
+module_exit(sg_pool_exit);