Re: [PATCH 3/3] zram: get rid of lockdep warning
From: Nitin Gupta
Date: Fri Jan 18 2013 - 16:34:05 EST
On Wed, Jan 16, 2013 at 6:12 PM, Minchan Kim <minchan@xxxxxxxxxx> wrote:
> Lockdep complains about recursive deadlock of zram->init_lock.
> [1] made it false positive because we can't request IO to zram
> before setting disksize. Anyway, we should shut lockdep up to
> avoid many reporting from user.
>
> This patch allocates zram's metadata out of lock so we can fix it.
> In addition, this patch replace GFP_KERNEL with GFP_NOIO/GFP_ATOMIC
> in request handle path for partial I/O.
>
> [1] zram: give up lazy initialization of zram metadata
>
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> drivers/staging/zram/zram_drv.c | 194 +++++++++++++++++++------------------
> drivers/staging/zram/zram_drv.h | 12 ++-
> drivers/staging/zram/zram_sysfs.c | 13 ++-
> 3 files changed, 118 insertions(+), 101 deletions(-)
>
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 3693780..eb1bc37 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -71,22 +71,22 @@ static void zram_stat64_inc(struct zram *zram, u64 *v)
> zram_stat64_add(zram, v, 1);
> }
>
> -static int zram_test_flag(struct zram *zram, u32 index,
> +static int zram_test_flag(struct zram_meta *meta, u32 index,
> enum zram_pageflags flag)
> {
> - return zram->table[index].flags & BIT(flag);
> + return meta->table[index].flags & BIT(flag);
> }
>
> -static void zram_set_flag(struct zram *zram, u32 index,
> +static void zram_set_flag(struct zram_meta *meta, u32 index,
> enum zram_pageflags flag)
> {
> - zram->table[index].flags |= BIT(flag);
> + meta->table[index].flags |= BIT(flag);
> }
>
> -static void zram_clear_flag(struct zram *zram, u32 index,
> +static void zram_clear_flag(struct zram_meta *meta, u32 index,
> enum zram_pageflags flag)
> {
> - zram->table[index].flags &= ~BIT(flag);
> + meta->table[index].flags &= ~BIT(flag);
> }
>
> static int page_zero_filled(void *ptr)
> @@ -106,16 +106,17 @@ static int page_zero_filled(void *ptr)
>
> static void zram_free_page(struct zram *zram, size_t index)
> {
> - unsigned long handle = zram->table[index].handle;
> - u16 size = zram->table[index].size;
> + struct zram_meta *meta = zram->meta;
> + unsigned long handle = meta->table[index].handle;
> + u16 size = meta->table[index].size;
>
> if (unlikely(!handle)) {
> /*
> * No memory is allocated for zero filled pages.
> * Simply clear zero page flag.
> */
> - if (zram_test_flag(zram, index, ZRAM_ZERO)) {
> - zram_clear_flag(zram, index, ZRAM_ZERO);
> + if (zram_test_flag(meta, index, ZRAM_ZERO)) {
> + zram_clear_flag(meta, index, ZRAM_ZERO);
> zram_stat_dec(&zram->stats.pages_zero);
> }
> return;
> @@ -124,17 +125,17 @@ static void zram_free_page(struct zram *zram, size_t index)
> if (unlikely(size > max_zpage_size))
> zram_stat_dec(&zram->stats.bad_compress);
>
> - zs_free(zram->mem_pool, handle);
> + zs_free(meta->mem_pool, handle);
>
> if (size <= PAGE_SIZE / 2)
> zram_stat_dec(&zram->stats.good_compress);
>
> zram_stat64_sub(zram, &zram->stats.compr_size,
> - zram->table[index].size);
> + meta->table[index].size);
> zram_stat_dec(&zram->stats.pages_stored);
>
> - zram->table[index].handle = 0;
> - zram->table[index].size = 0;
> + meta->table[index].handle = 0;
> + meta->table[index].size = 0;
> }
>
> static void handle_zero_page(struct bio_vec *bvec)
> @@ -159,20 +160,21 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> int ret = LZO_E_OK;
> size_t clen = PAGE_SIZE;
> unsigned char *cmem;
> - unsigned long handle = zram->table[index].handle;
> + struct zram_meta *meta = zram->meta;
> + unsigned long handle = meta->table[index].handle;
>
> - if (!handle || zram_test_flag(zram, index, ZRAM_ZERO)) {
> + if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
> memset(mem, 0, PAGE_SIZE);
> return 0;
> }
>
> - cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
> - if (zram->table[index].size == PAGE_SIZE)
> + cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
> + if (meta->table[index].size == PAGE_SIZE)
> memcpy(mem, cmem, PAGE_SIZE);
> else
> - ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
> + ret = lzo1x_decompress_safe(cmem, meta->table[index].size,
> mem, &clen);
> - zs_unmap_object(zram->mem_pool, handle);
> + zs_unmap_object(meta->mem_pool, handle);
>
> /* Should NEVER happen. Return bio error if it does. */
> if (unlikely(ret != LZO_E_OK)) {
> @@ -190,11 +192,11 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
> int ret;
> struct page *page;
> unsigned char *user_mem, *uncmem = NULL;
> -
> + struct zram_meta *meta = zram->meta;
> page = bvec->bv_page;
>
> - if (unlikely(!zram->table[index].handle) ||
> - zram_test_flag(zram, index, ZRAM_ZERO)) {
> + if (unlikely(!meta->table[index].handle) ||
> + zram_test_flag(meta, index, ZRAM_ZERO)) {
> handle_zero_page(bvec);
> return 0;
> }
> @@ -202,7 +204,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
> user_mem = kmap_atomic(page);
> if (is_partial_io(bvec))
> /* Use a temporary buffer to decompress the page */
> - uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
> + uncmem = kmalloc(PAGE_SIZE, GFP_ATOMIC);
> else
> uncmem = user_mem;
>
> @@ -241,16 +243,17 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> unsigned long handle;
> struct page *page;
> unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
> + struct zram_meta *meta = zram->meta;
>
> page = bvec->bv_page;
> - src = zram->compress_buffer;
> + src = meta->compress_buffer;
>
> 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_KERNEL);
> + uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
> if (!uncmem) {
> pr_info("Error allocating temp memory!\n");
> ret = -ENOMEM;
> @@ -265,8 +268,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> * System overwrites unused sectors. Free memory associated
> * with this sector now.
> */
> - if (zram->table[index].handle ||
> - zram_test_flag(zram, index, ZRAM_ZERO))
> + if (meta->table[index].handle ||
> + zram_test_flag(meta, index, ZRAM_ZERO))
> zram_free_page(zram, index);
>
> user_mem = kmap_atomic(page);
> @@ -284,13 +287,13 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> if (!is_partial_io(bvec))
> kunmap_atomic(user_mem);
> zram_stat_inc(&zram->stats.pages_zero);
> - zram_set_flag(zram, index, ZRAM_ZERO);
> + zram_set_flag(meta, index, ZRAM_ZERO);
> ret = 0;
> goto out;
> }
>
> ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
> - zram->compress_workmem);
> + meta->compress_workmem);
>
> if (!is_partial_io(bvec)) {
> kunmap_atomic(user_mem);
> @@ -311,14 +314,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> src = uncmem;
> }
>
> - handle = zs_malloc(zram->mem_pool, clen);
> + handle = zs_malloc(meta->mem_pool, clen);
> if (!handle) {
> pr_info("Error allocating memory for compressed "
> "page: %u, size=%zu\n", index, clen);
> ret = -ENOMEM;
> goto out;
> }
> - cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
> + cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
>
> if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
> src = kmap_atomic(page);
> @@ -326,10 +329,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
> kunmap_atomic(src);
>
> - zs_unmap_object(zram->mem_pool, handle);
> + zs_unmap_object(meta->mem_pool, handle);
>
> - zram->table[index].handle = handle;
> - zram->table[index].size = clen;
> + meta->table[index].handle = handle;
> + meta->table[index].size = clen;
>
> /* Update stats */
> zram_stat64_add(zram, &zram->stats.compr_size, clen);
> @@ -472,33 +475,24 @@ error:
> void __zram_reset_device(struct zram *zram)
> {
> size_t index;
> + struct zram_meta *meta;
>
> if (!zram->init_done)
> goto out;
>
> + meta = zram->meta;
> zram->init_done = 0;
> -
> - /* Free various per-device buffers */
> - kfree(zram->compress_workmem);
> - free_pages((unsigned long)zram->compress_buffer, 1);
> -
> - zram->compress_workmem = NULL;
> - zram->compress_buffer = NULL;
> -
> /* Free all pages that are still in this zram device */
> for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
> - unsigned long handle = zram->table[index].handle;
> + unsigned long handle = meta->table[index].handle;
> if (!handle)
> continue;
>
> - zs_free(zram->mem_pool, handle);
> + zs_free(meta->mem_pool, handle);
> }
>
> - vfree(zram->table);
> - zram->table = NULL;
> -
> - zs_destroy_pool(zram->mem_pool);
> - zram->mem_pool = NULL;
> + zram_meta_free(zram->meta);
> + zram->meta = NULL;
>
> /* Reset stats */
> memset(&zram->stats, 0, sizeof(zram->stats));
> @@ -514,12 +508,64 @@ void zram_reset_device(struct zram *zram)
> up_write(&zram->init_lock);
> }
>
> -/* zram->init_lock should be held */
> -int zram_init_device(struct zram *zram)
> +void zram_meta_free(struct zram_meta *meta)
> {
> - int ret;
> - size_t num_pages;
> + zs_destroy_pool(meta->mem_pool);
> + kfree(meta->compress_workmem);
> + free_pages((unsigned long)meta->compress_buffer, 1);
> + vfree(meta->table);
> + kfree(meta);
> +}
> +
> +struct zram_meta *zram_meta_alloc(u64 disksize)
> +{
> + size_t num_pages;
> + struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
> + if (!meta)
> + goto out;
> +
> + meta->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> + if (!meta->compress_workmem) {
> + pr_err("Error allocating compressor working memory!\n");
> + goto free_meta;
> + }
> +
> + meta->compress_buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> + if (!meta->compress_buffer) {
> + pr_err("Error allocating compressor buffer space\n");
> + goto free_workmem;
> + }
> +
> + num_pages = disksize >> PAGE_SHIFT;
> + meta->table = vzalloc(num_pages * sizeof(*meta->table));
> + if (!meta->table) {
> + pr_err("Error allocating zram address table\n");
> + goto free_buffer;
> + }
> +
> + meta->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
> + if (!meta->mem_pool) {
> + pr_err("Error creating memory pool\n");
> + goto free_table;
> + }
> +
> + return meta;
> +
> +free_table:
> + vfree(meta->table);
> +free_buffer:
> + free_pages((unsigned long)meta->compress_buffer, 1);
> +free_workmem:
> + kfree(meta->compress_workmem);
> +free_meta:
> + kfree(meta);
> + meta = NULL;
> +out:
> + return meta;
> +}
>
> +void zram_init_device(struct zram *zram, struct zram_meta *meta)
> +{
> if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) {
> pr_info(
> "There is little point creating a zram of greater than "
> @@ -534,51 +580,13 @@ int zram_init_device(struct zram *zram)
> );
> }
>
> - zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> - if (!zram->compress_workmem) {
> - pr_err("Error allocating compressor working memory!\n");
> - ret = -ENOMEM;
> - goto fail_no_table;
> - }
> -
> - zram->compress_buffer =
> - (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> - if (!zram->compress_buffer) {
> - pr_err("Error allocating compressor buffer space\n");
> - ret = -ENOMEM;
> - goto fail_no_table;
> - }
> -
> - num_pages = zram->disksize >> PAGE_SHIFT;
> - zram->table = vzalloc(num_pages * sizeof(*zram->table));
> - if (!zram->table) {
> - pr_err("Error allocating zram address table\n");
> - ret = -ENOMEM;
> - goto fail_no_table;
> - }
> -
> /* zram devices sort of resembles non-rotational disks */
> queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
>
> - zram->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
> - if (!zram->mem_pool) {
> - pr_err("Error creating memory pool\n");
> - ret = -ENOMEM;
> - goto fail;
> - }
> -
> + zram->meta = meta;
> zram->init_done = 1;
>
> pr_debug("Initialization done!\n");
> - return 0;
> -
> -fail_no_table:
> - /* To prevent accessing table entries during cleanup */
> - zram->disksize = 0;
> -fail:
> - __zram_reset_device(zram);
> - pr_err("Initialization failed: err=%d\n", ret);
> - return ret;
> }
>
> static void zram_slot_free_notify(struct block_device *bdev,
> diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
> index 5b671d1..2d1a3f1 100644
> --- a/drivers/staging/zram/zram_drv.h
> +++ b/drivers/staging/zram/zram_drv.h
> @@ -83,11 +83,15 @@ struct zram_stats {
> u32 bad_compress; /* % of pages with compression ratio>=75% */
> };
>
> -struct zram {
> - struct zs_pool *mem_pool;
> +struct zram_meta {
> void *compress_workmem;
> void *compress_buffer;
> struct table *table;
> + struct zs_pool *mem_pool;
> +};
> +
> +struct zram {
> + struct zram_meta *meta;
> spinlock_t stat64_lock; /* protect 64-bit stats */
> struct rw_semaphore lock; /* protect compression buffers and table
> * against concurrent read and writes */
> @@ -111,7 +115,9 @@ unsigned int zram_get_num_devices(void);
> extern struct attribute_group zram_disk_attr_group;
> #endif
>
> -extern int zram_init_device(struct zram *zram);
> extern void zram_reset_device(struct zram *zram);
> +extern struct zram_meta *zram_meta_alloc(u64 disksize);
> +extern void zram_meta_free(struct zram_meta *meta);
> +extern void zram_init_device(struct zram *zram, struct zram_meta *meta);
>
This separation of zram and zram_meta looks weird and unncessary. I
would prefer just having
a single struct zram as before.
Thanks,
Nitin
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