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Subject[PATCH v2 2/6] zram: partial IO refactoring
Date
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.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
drivers/block/zram/zram_drv.c | 337 +++++++++++++++++++++++-------------------
1 file changed, 184 insertions(+), 153 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 9c3f862b72f4..c4445995fd13 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)
{
@@ -191,18 +200,6 @@ 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)
{
@@ -418,6 +415,53 @@ 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;
@@ -504,169 +548,103 @@ 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:
@@ -682,27 +660,21 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
* 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);
@@ -710,22 +682,45 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,

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);

/*
@@ -734,19 +729,54 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
*/
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;
}

@@ -802,6 +832,7 @@ 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);
--
2.7.4
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