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 via factoring out partial IO
routines to zram_bvec_partial_[read|write] which will be disabled
for most 4K page architecures.
x86(4K architecure)
add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-664 (-664)
function old new delta
zram_bvec_rw 2301 2039 -262
zram_decompress_page.isra 402 - -402
So, we will save 662 bytes.
However, as side effect, it will increase binary size in
non-4K architecure but it's not major for zram so I believe
benefit(maintainance, binary size for most architecture) is bigger.
Cc: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
drivers/block/zram/zram_drv.c | 259 ++++++++++++++++++++++++++++++------------
1 file changed, 186 insertions(+), 73 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index fefdf260503a..0f92dae177d6 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -98,10 +98,17 @@ 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)
{
@@ -543,8 +550,8 @@ static int zram_decompress_page(struct zram *zram, char
*mem, u32 index)
return 0;
}
-static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
- u32 index, int offset)
+static int zram_bvec_partial_read(struct zram *zram, struct bio_vec *bvec,
+ u32 index, int offset)
{
int ret;
struct page *page;
@@ -561,81 +568,87 @@ static int zram_bvec_read(struct zram *zram, struct
bio_vec *bvec,
}
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);
-
- user_mem = kmap_atomic(page);
- if (!is_partial_io(bvec))
- uncmem = user_mem;
-
+ /* Use a temporary buffer to decompress the page */
+ uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
if (!uncmem) {
pr_err("Unable to allocate temp memory\n");
- ret = -ENOMEM;
- goto out_cleanup;
+ return -ENOMEM;
}
+ user_mem = kmap_atomic(page);
ret = zram_decompress_page(zram, uncmem, index);
- /* Should NEVER happen. Return bio error if it does. */
if (unlikely(ret))
goto out_cleanup;
- if (is_partial_io(bvec))
- memcpy(user_mem + bvec->bv_offset, uncmem + offset,
+ memcpy(user_mem + bvec->bv_offset, uncmem + offset,
bvec->bv_len);
-
flush_dcache_page(page);
ret = 0;
out_cleanup:
kunmap_atomic(user_mem);
- if (is_partial_io(bvec))
- kfree(uncmem);
+ kfree(uncmem);
return ret;
}
-static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
- int offset)
+static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
+ u32 index, int offset)
{
- int ret = 0;
+ int ret;
+ struct page *page;
+ unsigned char *user_mem;
+ 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;
+ }
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+ user_mem = kmap_atomic(page);
+ ret = zram_decompress_page(zram, user_mem, index);
+ kunmap_atomic(user_mem);
+
+ flush_dcache_page(page);
+ return ret;
+}
+
+static int zram_bvec_partial_write(struct zram *zram, struct bio_vec *bvec,
+ u32 index, int offset)
+{
+ int ret = -ENOMEM;
unsigned int clen;
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;
+ struct zcomp_strm *zstrm;
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;
- }
+ /*
+ * 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)
+ return ret;
+
+ 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;
- }
+ memcpy(uncmem + offset, user_mem + bvec->bv_offset,
+ bvec->bv_len);
+ kunmap_atomic(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);
@@ -650,13 +663,8 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
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;
- }
-
if (unlikely(ret)) {
+ zcomp_stream_put(zram->comp);
pr_err("Compression failed! err=%d\n", ret);
goto out;
}
@@ -664,8 +672,7 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
src = zstrm->buffer;
if (unlikely(clen > max_zpage_size)) {
clen = PAGE_SIZE;
- if (is_partial_io(bvec))
- src = uncmem;
+ src = uncmem;
}
/*
@@ -689,8 +696,6 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
__GFP_MOVABLE);
if (!handle) {
zcomp_stream_put(zram->comp);
- zstrm = NULL;
-
atomic64_inc(&zram->stats.writestall);
handle = zs_malloc(meta->mem_pool, clen,
@@ -701,7 +706,6 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
pr_err("Error allocating memory for compressed page: %u,
size=%u\n",
index, clen);
- ret = -ENOMEM;
goto out;
}
@@ -710,22 +714,131 @@ 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;
+ zcomp_stream_put(zram->comp);
goto out;
}
cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
- if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
- src = kmap_atomic(page);
- copy_page(cmem, src);
- kunmap_atomic(src);
+ memcpy(cmem, src, clen);
+ zcomp_stream_put(zram->comp);
+ zs_unmap_object(meta->mem_pool, handle);
+
+ /*
+ * Free memory associated with this sector
+ * before overwriting unused sectors.
+ */
+ 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);
+ bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+ /* Update stats */
+ atomic64_add(clen, &zram->stats.compr_data_size);
+ atomic64_inc(&zram->stats.pages_stored);
+ ret = 0;
+out:
+ kfree(uncmem);
+ return ret;
+}
+
+static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
+ int offset)
+{
+ int ret;
+ unsigned int clen;
+ unsigned long handle = 0;
+ struct page *page;
+ void *user_mem, *cmem;
+ struct zram_meta *meta = zram->meta;
+ struct zcomp_strm *zstrm;
+ unsigned long alloced_pages;
+ unsigned long element;
+
+ page = bvec->bv_page;
+compress_again:
+ user_mem = kmap_atomic(page);
+ if (page_same_filled(user_mem, &element)) {
+ 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);
+ return 0;
+ }
+
+ zstrm = zcomp_stream_get(zram->comp);
+ ret = zcomp_compress(zstrm, user_mem, &clen);
+ kunmap_atomic(user_mem);
+
+ if (unlikely(ret)) {
+ pr_err("Compression failed! err=%d\n", ret);
+ zcomp_stream_put(zram->comp);
+ return ret;
+ }
+
+ if (unlikely(clen > max_zpage_size))
+ clen = PAGE_SIZE;
+
+ /*
+ * handle allocation has 2 paths:
+ * a) fast path is executed with preemption disabled (for
+ * per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
+ * since we can't sleep;
+ * b) slow path enables preemption and attempts to allocate
+ * the page with __GFP_DIRECT_RECLAIM bit set. we have to
+ * put per-cpu compression stream and, thus, to re-do
+ * the compression once handle is allocated.
+ *
+ * if we have a 'non-null' handle here then we are coming
+ * from the slow path and handle has already been allocated.
+ */
+ if (!handle)
+ handle = zs_malloc(meta->mem_pool, clen,
+ __GFP_KSWAPD_RECLAIM |
+ __GFP_NOWARN |
+ __GFP_HIGHMEM |
+ __GFP_MOVABLE);
+ if (!handle) {
+ zcomp_stream_put(zram->comp);
+ atomic64_inc(&zram->stats.writestall);
+ handle = zs_malloc(meta->mem_pool, clen,
+ GFP_NOIO | __GFP_HIGHMEM |
+ __GFP_MOVABLE);
+ if (handle)
+ goto compress_again;
+
+ pr_err("Error allocating memory for compressed page: %u,
size=%u\n",
+ index, clen);
+ return -ENOMEM;
+ }
+
+ alloced_pages = zs_get_total_pages(meta->mem_pool);
+ update_used_max(zram, alloced_pages);
+
+ if (zram->limit_pages && alloced_pages > zram->limit_pages) {
+ zs_free(meta->mem_pool, handle);
+ zcomp_stream_put(zram->comp);
+ return -ENOMEM;
+ }
+
+ cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
+
+ if (clen == PAGE_SIZE) {
+ user_mem = kmap_atomic(page);
+ copy_page(cmem, user_mem);
+ kunmap_atomic(user_mem);
} else {
- memcpy(cmem, src, clen);
+ memcpy(cmem, zstrm->buffer, clen);
}
zcomp_stream_put(zram->comp);
- zstrm = NULL;
zs_unmap_object(meta->mem_pool, handle);
/*
@@ -734,7 +847,6 @@ 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);
bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
@@ -742,12 +854,7 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
/* Update stats */
atomic64_add(clen, &zram->stats.compr_data_size);
atomic64_inc(&zram->stats.pages_stored);
-out:
- if (zstrm)
- zcomp_stream_put(zram->comp);
- if (is_partial_io(bvec))
- kfree(uncmem);
- return ret;
+ return 0;
}
/*
@@ -801,10 +908,16 @@ 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);
+ if (!is_partial_io(bvec))
+ ret = zram_bvec_read(zram, bvec, index, offset);
+ else
+ ret = zram_bvec_partial_read(zram, bvec, index, offset);
} else {
atomic64_inc(&zram->stats.num_writes);
- ret = zram_bvec_write(zram, bvec, index, offset);
+ if (!is_partial_io(bvec))
+ ret = zram_bvec_write(zram, bvec, index, offset);
+ else
+ ret = zram_bvec_partial_write(zram, bvec, index,
offset);
}
generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
--
2.7.4
