zram: partial IO refactoring

For architecture(PAGE_SIZE > 4K), zram have supported partial IO.
However, the mixed code for handling normal/partial IO is too mess,
error-prone to modify IO handler functions with upcoming feature so this
patch aims for cleaning up zram's IO handling functions.

Link: http://lkml.kernel.org/r/1492052365-16169-3-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 184 insertions, 153 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8a38ff0c16a3..47e15fec3cd0 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -45,6 +45,8 @@ static const char *default_compressor = "lzo";
 /* Module params (documentation at end) */
 static unsigned int num_devices = 1;
 
+static void zram_free_page(struct zram *zram, size_t index);
+
 static inline bool init_done(struct zram *zram)
 {
         return zram->disksize;
@@ -98,10 +100,17 @@ static void zram_set_obj_size(struct zram_meta *meta,
         meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
 }
 
+#if PAGE_SIZE != 4096
 static inline bool is_partial_io(struct bio_vec *bvec)
 {
         return bvec->bv_len != PAGE_SIZE;
 }
+#else
+static inline bool is_partial_io(struct bio_vec *bvec)
+{
+        return false;
+}
+#endif
 
 static void zram_revalidate_disk(struct zram *zram)
 {
@@ -189,18 +198,6 @@ static bool page_same_filled(void *ptr, unsigned long *element)
         return true;
 }
 
-static void handle_same_page(struct bio_vec *bvec, unsigned long element)
-{
-        struct page *page = bvec->bv_page;
-        void *user_mem;
-
-        user_mem = kmap_atomic(page);
-        zram_fill_page(user_mem + bvec->bv_offset, bvec->bv_len, element);
-        kunmap_atomic(user_mem);
-
-        flush_dcache_page(page);
-}
-
 static ssize_t initstate_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
@@ -416,6 +413,53 @@ static DEVICE_ATTR_RO(io_stat);
 static DEVICE_ATTR_RO(mm_stat);
 static DEVICE_ATTR_RO(debug_stat);
 
+static bool zram_same_page_read(struct zram *zram, u32 index,
+                                struct page *page,
+                                unsigned int offset, unsigned int len)
+{
+        struct zram_meta *meta = zram->meta;
+
+        bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+        if (unlikely(!meta->table[index].handle) ||
+                        zram_test_flag(meta, index, ZRAM_SAME)) {
+                void *mem;
+
+                bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+                mem = kmap_atomic(page);
+                zram_fill_page(mem + offset, len, meta->table[index].element);
+                kunmap_atomic(mem);
+                return true;
+        }
+        bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+        return false;
+}
+
+static bool zram_same_page_write(struct zram *zram, u32 index,
+                                        struct page *page)
+{
+        unsigned long element;
+        void *mem = kmap_atomic(page);
+
+        if (page_same_filled(mem, &element)) {
+                struct zram_meta *meta = zram->meta;
+
+                kunmap_atomic(mem);
+                /* Free memory associated with this sector now. */
+                bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+                zram_free_page(zram, index);
+                zram_set_flag(meta, index, ZRAM_SAME);
+                zram_set_element(meta, index, element);
+                bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+                atomic64_inc(&zram->stats.same_pages);
+                return true;
+        }
+        kunmap_atomic(mem);
+
+        return false;
+}
+
 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 {
         size_t num_pages = disksize >> PAGE_SHIFT;
@@ -502,169 +546,103 @@ static void zram_free_page(struct zram *zram, size_t index)
         zram_set_obj_size(meta, index, 0);
 }
 
-static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
+static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
 {
-        int ret = 0;
-        unsigned char *cmem;
-        struct zram_meta *meta = zram->meta;
+        int ret;
         unsigned long handle;
         unsigned int size;
+        void *src, *dst;
+        struct zram_meta *meta = zram->meta;
+
+        if (zram_same_page_read(zram, index, page, 0, PAGE_SIZE))
+                return 0;
 
         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
         handle = meta->table[index].handle;
         size = zram_get_obj_size(meta, index);
 
-        if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) {
-                bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
-                zram_fill_page(mem, PAGE_SIZE, meta->table[index].element);
-                return 0;
-        }
-
-        cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
+        src = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
         if (size == PAGE_SIZE) {
-                memcpy(mem, cmem, PAGE_SIZE);
+                dst = kmap_atomic(page);
+                memcpy(dst, src, PAGE_SIZE);
+                kunmap_atomic(dst);
+                ret = 0;
         } else {
                 struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
 
-                ret = zcomp_decompress(zstrm, cmem, size, mem);
+                dst = kmap_atomic(page);
+                ret = zcomp_decompress(zstrm, src, size, dst);
+                kunmap_atomic(dst);
                 zcomp_stream_put(zram->comp);
         }
         zs_unmap_object(meta->mem_pool, handle);
         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
         /* Should NEVER happen. Return bio error if it does. */
-        if (unlikely(ret)) {
+        if (unlikely(ret))
                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
-                return ret;
-        }
 
-        return 0;
+        return ret;
 }
 
 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
-                          u32 index, int offset)
+                                u32 index, int offset)
 {
         int ret;
         struct page *page;
-        unsigned char *user_mem, *uncmem = NULL;
-        struct zram_meta *meta = zram->meta;
-        page = bvec->bv_page;
 
-        bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
-        if (unlikely(!meta->table[index].handle) ||
-                        zram_test_flag(meta, index, ZRAM_SAME)) {
-                bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
-                handle_same_page(bvec, meta->table[index].element);
-                return 0;
+        page = bvec->bv_page;
+        if (is_partial_io(bvec)) {
+                /* Use a temporary buffer to decompress the page */
+                page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
+                if (!page)
+                        return -ENOMEM;
         }
-        bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
-        if (is_partial_io(bvec))
-                /* Use  a temporary buffer to decompress the page */
-                uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
+        ret = zram_decompress_page(zram, page, index);
+        if (unlikely(ret))
+                goto out;
 
-        user_mem = kmap_atomic(page);
-        if (!is_partial_io(bvec))
-                uncmem = user_mem;
+        if (is_partial_io(bvec)) {
+                void *dst = kmap_atomic(bvec->bv_page);
+                void *src = kmap_atomic(page);
 
-        if (!uncmem) {
-                pr_err("Unable to allocate temp memory\n");
-                ret = -ENOMEM;
-                goto out_cleanup;
+                memcpy(dst + bvec->bv_offset, src + offset, bvec->bv_len);
+                kunmap_atomic(src);
+                kunmap_atomic(dst);
         }
-
-        ret = zram_decompress_page(zram, uncmem, index);
-        /* Should NEVER happen. Return bio error if it does. */
-        if (unlikely(ret))
-                goto out_cleanup;
-
+out:
         if (is_partial_io(bvec))
-                memcpy(user_mem + bvec->bv_offset, uncmem + offset,
-                                bvec->bv_len);
+                __free_page(page);
 
-        flush_dcache_page(page);
-        ret = 0;
-out_cleanup:
-        kunmap_atomic(user_mem);
-        if (is_partial_io(bvec))
-                kfree(uncmem);
         return ret;
 }
 
-static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
-                           int offset)
+static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
+                        struct page *page,
+                        unsigned long *out_handle, unsigned int *out_comp_len)
 {
-        int ret = 0;
-        unsigned int clen;
+        int ret;
+        unsigned int comp_len;
+        void *src;
+        unsigned long alloced_pages;
         unsigned long handle = 0;
-        struct page *page;
-        unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
         struct zram_meta *meta = zram->meta;
-        struct zcomp_strm *zstrm = NULL;
-        unsigned long alloced_pages;
-        unsigned long element;
-
-        page = bvec->bv_page;
-        if (is_partial_io(bvec)) {
-                /*
-                 * This is a partial IO. We need to read the full page
-                 * before to write the changes.
-                 */
-                uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
-                if (!uncmem) {
-                        ret = -ENOMEM;
-                        goto out;
-                }
-                ret = zram_decompress_page(zram, uncmem, index);
-                if (ret)
-                        goto out;
-        }
 
 compress_again:
-        user_mem = kmap_atomic(page);
-        if (is_partial_io(bvec)) {
-                memcpy(uncmem + offset, user_mem + bvec->bv_offset,
-                       bvec->bv_len);
-                kunmap_atomic(user_mem);
-                user_mem = NULL;
-        } else {
-                uncmem = user_mem;
-        }
-
-        if (page_same_filled(uncmem, &element)) {
-                if (user_mem)
-                        kunmap_atomic(user_mem);
-                /* Free memory associated with this sector now. */
-                bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
-                zram_free_page(zram, index);
-                zram_set_flag(meta, index, ZRAM_SAME);
-                zram_set_element(meta, index, element);
-                bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
-
-                atomic64_inc(&zram->stats.same_pages);
-                ret = 0;
-                goto out;
-        }
-
-        zstrm = zcomp_stream_get(zram->comp);
-        ret = zcomp_compress(zstrm, uncmem, &clen);
-        if (!is_partial_io(bvec)) {
-                kunmap_atomic(user_mem);
-                user_mem = NULL;
-                uncmem = NULL;
-        }
+        src = kmap_atomic(page);
+        ret = zcomp_compress(*zstrm, src, &comp_len);
+        kunmap_atomic(src);
 
         if (unlikely(ret)) {
                 pr_err("Compression failed! err=%d\n", ret);
-                goto out;
+                if (handle)
+                        zs_free(meta->mem_pool, handle);
+                return ret;
         }
 
-        src = zstrm->buffer;
-        if (unlikely(clen > max_zpage_size)) {
-                clen = PAGE_SIZE;
-                if (is_partial_io(bvec))
-                        src = uncmem;
-        }
+        if (unlikely(comp_len > max_zpage_size))
+                comp_len = PAGE_SIZE;
 
         /*
          * handle allocation has 2 paths:
@@ -680,27 +658,21 @@ compress_again:
          * from the slow path and handle has already been allocated.
          */
         if (!handle)
-                handle = zs_malloc(meta->mem_pool, clen,
+                handle = zs_malloc(meta->mem_pool, comp_len,
                                 __GFP_KSWAPD_RECLAIM |
                                 __GFP_NOWARN |
                                 __GFP_HIGHMEM |
                                 __GFP_MOVABLE);
         if (!handle) {
                 zcomp_stream_put(zram->comp);
-                zstrm = NULL;
-
                 atomic64_inc(&zram->stats.writestall);
-
-                handle = zs_malloc(meta->mem_pool, clen,
+                handle = zs_malloc(meta->mem_pool, comp_len,
                                 GFP_NOIO | __GFP_HIGHMEM |
                                 __GFP_MOVABLE);
+                *zstrm = zcomp_stream_get(zram->comp);
                 if (handle)
                         goto compress_again;
-
-                pr_err("Error allocating memory for compressed page: %u, size=%u\n",
-                        index, clen);
-                ret = -ENOMEM;
-                goto out;
+                return -ENOMEM;
         }
 
         alloced_pages = zs_get_total_pages(meta->mem_pool);
@@ -708,22 +680,45 @@ compress_again:
 
         if (zram->limit_pages && alloced_pages > zram->limit_pages) {
                 zs_free(meta->mem_pool, handle);
-                ret = -ENOMEM;
-                goto out;
+                return -ENOMEM;
         }
 
-        cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
+        *out_handle = handle;
+        *out_comp_len = comp_len;
+        return 0;
+}
 
-        if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
+static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
+{
+        int ret;
+        unsigned long handle;
+        unsigned int comp_len;
+        void *src, *dst;
+        struct zcomp_strm *zstrm;
+        struct zram_meta *meta = zram->meta;
+        struct page *page = bvec->bv_page;
+
+        if (zram_same_page_write(zram, index, page))
+                return 0;
+
+        zstrm = zcomp_stream_get(zram->comp);
+        ret = zram_compress(zram, &zstrm, page, &handle, &comp_len);
+        if (ret) {
+                zcomp_stream_put(zram->comp);
+                return ret;
+        }
+
+
+        dst = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
+
+        src = zstrm->buffer;
+        if (comp_len == PAGE_SIZE)
                 src = kmap_atomic(page);
-                memcpy(cmem, src, PAGE_SIZE);
+        memcpy(dst, src, comp_len);
+        if (comp_len == PAGE_SIZE)
                 kunmap_atomic(src);
-        } else {
-                memcpy(cmem, src, clen);
-        }
 
         zcomp_stream_put(zram->comp);
-        zstrm = NULL;
         zs_unmap_object(meta->mem_pool, handle);
 
         /*
@@ -732,19 +727,54 @@ compress_again:
          */
         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
         zram_free_page(zram, index);
-
         meta->table[index].handle = handle;
-        zram_set_obj_size(meta, index, clen);
+        zram_set_obj_size(meta, index, comp_len);
         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
         /* Update stats */
-        atomic64_add(clen, &zram->stats.compr_data_size);
+        atomic64_add(comp_len, &zram->stats.compr_data_size);
         atomic64_inc(&zram->stats.pages_stored);
+        return 0;
+}
+
+static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
+                                u32 index, int offset)
+{
+        int ret;
+        struct page *page = NULL;
+        void *src;
+        struct bio_vec vec;
+
+        vec = *bvec;
+        if (is_partial_io(bvec)) {
+                void *dst;
+                /*
+                 * This is a partial IO. We need to read the full page
+                 * before to write the changes.
+                 */
+                page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
+                if (!page)
+                        return -ENOMEM;
+
+                ret = zram_decompress_page(zram, page, index);
+                if (ret)
+                        goto out;
+
+                src = kmap_atomic(bvec->bv_page);
+                dst = kmap_atomic(page);
+                memcpy(dst + offset, src + bvec->bv_offset, bvec->bv_len);
+                kunmap_atomic(dst);
+                kunmap_atomic(src);
+
+                vec.bv_page = page;
+                vec.bv_len = PAGE_SIZE;
+                vec.bv_offset = 0;
+        }
+
+        ret = __zram_bvec_write(zram, &vec, index);
 out:
-        if (zstrm)
-                zcomp_stream_put(zram->comp);
         if (is_partial_io(bvec))
-                kfree(uncmem);
+                __free_page(page);
         return ret;
 }
 
@@ -800,6 +830,7 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
         if (!is_write) {
                 atomic64_inc(&zram->stats.num_reads);
                 ret = zram_bvec_read(zram, bvec, index, offset);
+                flush_dcache_page(bvec->bv_page);
         } else {
                 atomic64_inc(&zram->stats.num_writes);
                 ret = zram_bvec_write(zram, bvec, index, offset);