[PATCH] BLOCK: Separate the bounce buffering code from the highmem code [try #6]

Move the bounce buffer code from mm/highmem.c to mm/bounce.c so that it can be
more easily disabled when the block layer is disabled.

!!!NOTE!!! There may be a bug in this code: Should init_emergency_pool() be
	   contingent on CONFIG_HIGHMEM?

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 302 insertions, 0 deletions

diff --git a/mm/bounce.c b/mm/bounce.c
new file mode 100644
index 000000000000..e4b62d2a4024
--- /dev/null
+++ b/mm/bounce.c
@@ -0,0 +1,302 @@
+/* bounce buffer handling for block devices
+ *
+ * - Split from highmem.c
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/swap.h>
+#include <linux/bio.h>
+#include <linux/pagemap.h>
+#include <linux/mempool.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/highmem.h>
+#include <linux/blktrace_api.h>
+#include <asm/tlbflush.h>
+
+#define POOL_SIZE       64
+#define ISA_POOL_SIZE   16
+
+static mempool_t *page_pool, *isa_page_pool;
+
+#ifdef CONFIG_HIGHMEM
+static __init int init_emergency_pool(void)
+{
+        struct sysinfo i;
+        si_meminfo(&i);
+        si_swapinfo(&i);
+
+        if (!i.totalhigh)
+                return 0;
+
+        page_pool = mempool_create_page_pool(POOL_SIZE, 0);
+        BUG_ON(!page_pool);
+        printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
+
+        return 0;
+}
+
+__initcall(init_emergency_pool);
+
+/*
+ * highmem version, map in to vec
+ */
+static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
+{
+        unsigned long flags;
+        unsigned char *vto;
+
+        local_irq_save(flags);
+        vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
+        memcpy(vto + to->bv_offset, vfrom, to->bv_len);
+        kunmap_atomic(vto, KM_BOUNCE_READ);
+        local_irq_restore(flags);
+}
+
+#else /* CONFIG_HIGHMEM */
+
+#define bounce_copy_vec(to, vfrom)      \
+        memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
+
+#endif /* CONFIG_HIGHMEM */
+
+/*
+ * allocate pages in the DMA region for the ISA pool
+ */
+static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
+{
+        return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
+}
+
+/*
+ * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
+ * as the max address, so check if the pool has already been created.
+ */
+int init_emergency_isa_pool(void)
+{
+        if (isa_page_pool)
+                return 0;
+
+        isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
+                                       mempool_free_pages, (void *) 0);
+        BUG_ON(!isa_page_pool);
+
+        printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
+        return 0;
+}
+
+/*
+ * Simple bounce buffer support for highmem pages. Depending on the
+ * queue gfp mask set, *to may or may not be a highmem page. kmap it
+ * always, it will do the Right Thing
+ */
+static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
+{
+        unsigned char *vfrom;
+        struct bio_vec *tovec, *fromvec;
+        int i;
+
+        __bio_for_each_segment(tovec, to, i, 0) {
+                fromvec = from->bi_io_vec + i;
+
+                /*
+                 * not bounced
+                 */
+                if (tovec->bv_page == fromvec->bv_page)
+                        continue;
+
+                /*
+                 * fromvec->bv_offset and fromvec->bv_len might have been
+                 * modified by the block layer, so use the original copy,
+                 * bounce_copy_vec already uses tovec->bv_len
+                 */
+                vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
+
+                flush_dcache_page(tovec->bv_page);
+                bounce_copy_vec(tovec, vfrom);
+        }
+}
+
+static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
+{
+        struct bio *bio_orig = bio->bi_private;
+        struct bio_vec *bvec, *org_vec;
+        int i;
+
+        if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
+                set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);
+
+        /*
+         * free up bounce indirect pages used
+         */
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                org_vec = bio_orig->bi_io_vec + i;
+                if (bvec->bv_page == org_vec->bv_page)
+                        continue;
+
+                dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
+                mempool_free(bvec->bv_page, pool);
+        }
+
+        bio_endio(bio_orig, bio_orig->bi_size, err);
+        bio_put(bio);
+}
+
+static int bounce_end_io_write(struct bio *bio, unsigned int bytes_done, int err)
+{
+        if (bio->bi_size)
+                return 1;
+
+        bounce_end_io(bio, page_pool, err);
+        return 0;
+}
+
+static int bounce_end_io_write_isa(struct bio *bio, unsigned int bytes_done, int err)
+{
+        if (bio->bi_size)
+                return 1;
+
+        bounce_end_io(bio, isa_page_pool, err);
+        return 0;
+}
+
+static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
+{
+        struct bio *bio_orig = bio->bi_private;
+
+        if (test_bit(BIO_UPTODATE, &bio->bi_flags))
+                copy_to_high_bio_irq(bio_orig, bio);
+
+        bounce_end_io(bio, pool, err);
+}
+
+static int bounce_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
+{
+        if (bio->bi_size)
+                return 1;
+
+        __bounce_end_io_read(bio, page_pool, err);
+        return 0;
+}
+
+static int bounce_end_io_read_isa(struct bio *bio, unsigned int bytes_done, int err)
+{
+        if (bio->bi_size)
+                return 1;
+
+        __bounce_end_io_read(bio, isa_page_pool, err);
+        return 0;
+}
+
+static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
+                               mempool_t *pool)
+{
+        struct page *page;
+        struct bio *bio = NULL;
+        int i, rw = bio_data_dir(*bio_orig);
+        struct bio_vec *to, *from;
+
+        bio_for_each_segment(from, *bio_orig, i) {
+                page = from->bv_page;
+
+                /*
+                 * is destination page below bounce pfn?
+                 */
+                if (page_to_pfn(page) < q->bounce_pfn)
+                        continue;
+
+                /*
+                 * irk, bounce it
+                 */
+                if (!bio)
+                        bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);
+
+                to = bio->bi_io_vec + i;
+
+                to->bv_page = mempool_alloc(pool, q->bounce_gfp);
+                to->bv_len = from->bv_len;
+                to->bv_offset = from->bv_offset;
+                inc_zone_page_state(to->bv_page, NR_BOUNCE);
+
+                if (rw == WRITE) {
+                        char *vto, *vfrom;
+
+                        flush_dcache_page(from->bv_page);
+                        vto = page_address(to->bv_page) + to->bv_offset;
+                        vfrom = kmap(from->bv_page) + from->bv_offset;
+                        memcpy(vto, vfrom, to->bv_len);
+                        kunmap(from->bv_page);
+                }
+        }
+
+        /*
+         * no pages bounced
+         */
+        if (!bio)
+                return;
+
+        /*
+         * at least one page was bounced, fill in possible non-highmem
+         * pages
+         */
+        __bio_for_each_segment(from, *bio_orig, i, 0) {
+                to = bio_iovec_idx(bio, i);
+                if (!to->bv_page) {
+                        to->bv_page = from->bv_page;
+                        to->bv_len = from->bv_len;
+                        to->bv_offset = from->bv_offset;
+                }
+        }
+
+        bio->bi_bdev = (*bio_orig)->bi_bdev;
+        bio->bi_flags |= (1 << BIO_BOUNCED);
+        bio->bi_sector = (*bio_orig)->bi_sector;
+        bio->bi_rw = (*bio_orig)->bi_rw;
+
+        bio->bi_vcnt = (*bio_orig)->bi_vcnt;
+        bio->bi_idx = (*bio_orig)->bi_idx;
+        bio->bi_size = (*bio_orig)->bi_size;
+
+        if (pool == page_pool) {
+                bio->bi_end_io = bounce_end_io_write;
+                if (rw == READ)
+                        bio->bi_end_io = bounce_end_io_read;
+        } else {
+                bio->bi_end_io = bounce_end_io_write_isa;
+                if (rw == READ)
+                        bio->bi_end_io = bounce_end_io_read_isa;
+        }
+
+        bio->bi_private = *bio_orig;
+        *bio_orig = bio;
+}
+
+void blk_queue_bounce(request_queue_t *q, struct bio **bio_orig)
+{
+        mempool_t *pool;
+
+        /*
+         * for non-isa bounce case, just check if the bounce pfn is equal
+         * to or bigger than the highest pfn in the system -- in that case,
+         * don't waste time iterating over bio segments
+         */
+        if (!(q->bounce_gfp & GFP_DMA)) {
+                if (q->bounce_pfn >= blk_max_pfn)
+                        return;
+                pool = page_pool;
+        } else {
+                BUG_ON(!isa_page_pool);
+                pool = isa_page_pool;
+        }
+
+        blk_add_trace_bio(q, *bio_orig, BLK_TA_BOUNCE);
+
+        /*
+         * slow path
+         */
+        __blk_queue_bounce(q, bio_orig, pool);
+}
+
+EXPORT_SYMBOL(blk_queue_bounce);