4 files changed, 81 insertions, 49 deletions

diff --git a/block/Kconfig b/block/Kconfig
index 7db9a411649d..3e97f2bc446f 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -5,14 +5,18 @@ menuconfig BLOCK
        bool "Enable the block layer" if EMBEDDED
        default y
        help
-         This permits the block layer to be removed from the kernel if it's not
-         needed (on some embedded devices for example).  If this option is
-         disabled, then blockdev files will become unusable and some
-         filesystems (such as ext3) will become unavailable.
+         Provide block layer support for the kernel.
 
-         This option will also disable SCSI character devices and USB storage
-         since they make use of various block layer definitions and
-         facilities.
+         Disable this option to remove the block layer support from the
+         kernel. This may be useful for embedded devices.
+
+         If this option is disabled:
+
+           - block device files will become unusable
+           - some filesystems (such as ext3) will become unavailable.
+
+         Also, SCSI character devices and USB storage will be disabled since
+         they make use of various block layer definitions and facilities.
 
          Say Y here unless you know you really don't want to mount disks and
          suchlike.
@@ -23,9 +27,20 @@ config LBD
         bool "Support for Large Block Devices"
         depends on !64BIT
         help
-          Say Y here if you want to attach large (bigger than 2TB) discs to
-          your machine, or if you want to have a raid or loopback device
-          bigger than 2TB.  Otherwise say N.
+          Enable block devices of size 2TB and larger.
+
+          This option is required to support the full capacity of large
+          (2TB+) block devices, including RAID, disk, Network Block Device,
+          Logical Volume Manager (LVM) and loopback.
+
+          For example, RAID devices are frequently bigger than the capacity
+          of the largest individual hard drive.
+
+          This option is not required if you have individual disk drives
+          which total 2TB+ and you are not aggregating the capacity into
+          a large block device (e.g. using RAID or LVM).
+
+          If unsure, say N.
 
 config BLK_DEV_IO_TRACE
         bool "Support for tracing block io actions"
@@ -33,19 +48,21 @@ config BLK_DEV_IO_TRACE
         select RELAY
         select DEBUG_FS
         help
-          Say Y here, if you want to be able to trace the block layer actions
+          Say Y here if you want to be able to trace the block layer actions
           on a given queue. Tracing allows you to see any traffic happening
-          on a block device queue. For more information (and the user space
-          support tools needed), fetch the blktrace app from:
+          on a block device queue. For more information (and the userspace
+          support tools needed), fetch the blktrace tools from:
 
           git://git.kernel.dk/blktrace.git
 
+          If unsure, say N.
+
 config LSF
         bool "Support for Large Single Files"
         depends on !64BIT
         help
-          Say Y here if you want to be able to handle very large files (bigger
-          than 2TB), otherwise say N.
+          Say Y here if you want to be able to handle very large files (2TB
+          and larger), otherwise say N.
 
           If unsure, say Y.
 
@@ -53,14 +70,16 @@ config BLK_DEV_BSG
         bool "Block layer SG support v4 (EXPERIMENTAL)"
         depends on EXPERIMENTAL
         ---help---
-        Saying Y here will enable generic SG (SCSI generic) v4 support
-        for any block device.
-
-        Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4
-        can handle complicated SCSI commands: tagged variable length cdbs
-        with bidirectional data transfers and generic request/response
-        protocols (e.g. Task Management Functions and SMP in Serial
-        Attached SCSI).
+          Saying Y here will enable generic SG (SCSI generic) v4 support
+          for any block device.
+
+          Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4
+          can handle complicated SCSI commands: tagged variable length cdbs
+          with bidirectional data transfers and generic request/response
+          protocols (e.g. Task Management Functions and SMP in Serial
+          Attached SCSI).
+
+          If unsure, say N.
 
 endif # BLOCK
 
diff --git a/block/blk-map.c b/block/blk-map.c
index c07d9c8317f4..3c942bd6422a 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <scsi/sg.h>            /* for struct sg_iovec */
 
 #include "blk.h"
 
@@ -140,25 +141,8 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
                 ubuf += ret;
         }
 
-        /*
-         * __blk_rq_map_user() copies the buffers if starting address
-         * or length isn't aligned to dma_pad_mask.  As the copied
-         * buffer is always page aligned, we know that there's enough
-         * room for padding.  Extend the last bio and update
-         * rq->data_len accordingly.
-         *
-         * On unmap, bio_uncopy_user() will use unmodified
-         * bio_map_data pointed to by bio->bi_private.
-         */
-        if (len & q->dma_pad_mask) {
-                unsigned int pad_len = (q->dma_pad_mask & ~len) + 1;
-                struct bio *tail = rq->biotail;
-
-                tail->bi_io_vec[tail->bi_vcnt - 1].bv_len += pad_len;
-                tail->bi_size += pad_len;
-
-                rq->extra_len += pad_len;
-        }
+        if (!bio_flagged(bio, BIO_USER_MAPPED))
+                rq->cmd_flags |= REQ_COPY_USER;
 
         rq->buffer = rq->data = NULL;
         return 0;
@@ -194,15 +178,26 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
                         struct sg_iovec *iov, int iov_count, unsigned int len)
 {
         struct bio *bio;
+        int i, read = rq_data_dir(rq) == READ;
+        int unaligned = 0;
 
         if (!iov || iov_count <= 0)
                 return -EINVAL;
 
-        /* we don't allow misaligned data like bio_map_user() does.  If the
-         * user is using sg, they're expected to know the alignment constraints
-         * and respect them accordingly */
-        bio = bio_map_user_iov(q, NULL, iov, iov_count,
-                                rq_data_dir(rq) == READ);
+        for (i = 0; i < iov_count; i++) {
+                unsigned long uaddr = (unsigned long)iov[i].iov_base;
+
+                if (uaddr & queue_dma_alignment(q)) {
+                        unaligned = 1;
+                        break;
+                }
+        }
+
+        if (unaligned || (q->dma_pad_mask & len))
+                bio = bio_copy_user_iov(q, iov, iov_count, read);
+        else
+                bio = bio_map_user_iov(q, NULL, iov, iov_count, read);
+
         if (IS_ERR(bio))
                 return PTR_ERR(bio);
 
@@ -212,6 +207,9 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
                 return -EINVAL;
         }
 
+        if (!bio_flagged(bio, BIO_USER_MAPPED))
+                rq->cmd_flags |= REQ_COPY_USER;
+
         bio_get(bio);
         blk_rq_bio_prep(q, rq, bio);
         rq->buffer = rq->data = NULL;
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 0f58616bcd7f..b5c5c4a9e3f0 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -220,6 +220,15 @@ new_segment:
                 bvprv = bvec;
         } /* segments in rq */
 
+
+        if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
+            (rq->data_len & q->dma_pad_mask)) {
+                unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
+
+                sg->length += pad_len;
+                rq->extra_len += pad_len;
+        }
+
         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
                 if (rq->cmd_flags & REQ_RW)
                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 54d0db116153..fc41d83be22b 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -276,9 +276,12 @@ int blk_register_queue(struct gendisk *disk)
 
         struct request_queue *q = disk->queue;
 
-        if (!q || !q->request_fn)
+        if (WARN_ON(!q))
                 return -ENXIO;
 
+        if (!q->request_fn)
+                return 0;
+
         ret = kobject_add(&q->kobj, kobject_get(&disk->dev.kobj),
                           "%s", "queue");
         if (ret < 0)
@@ -300,7 +303,10 @@ void blk_unregister_queue(struct gendisk *disk)
 {
         struct request_queue *q = disk->queue;
 
-        if (q && q->request_fn) {
+        if (WARN_ON(!q))
+                return;
+
+        if (q->request_fn) {
                 elv_unregister_queue(q);
 
                 kobject_uevent(&q->kobj, KOBJ_REMOVE);