Re: [PATCH v7 4/4] zram: get rid of lockdep warning

From: Ric Mason
Date: Tue Feb 05 2013 - 01:20:07 EST

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In reply to: Minchan Kim: "Re: [PATCH v7 4/4] zram: get rid of lockdep warning"
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On Tue, 2013-02-05 at 15:06 +0900, Minchan Kim wrote:
> On Mon, Feb 04, 2013 at 01:39:24AM -0600, Ric Mason wrote:
> > On Mon, 2013-02-04 at 08:46 +0900, Minchan Kim 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.
> > >
> > > [1] : zram: force disksize setting before using zram
> > >
> > > Acked-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
> > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> > > ---
> > > drivers/staging/zram/zram_drv.c | 189 +++++++++++++++++++------------------
> > > drivers/staging/zram/zram_drv.h | 12 ++-
> > > drivers/staging/zram/zram_sysfs.c | 11 ++-
> > > 3 files changed, 116 insertions(+), 96 deletions(-)
> > >
> > > diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> > > index 85055c4..56e3203 100644
> > > --- a/drivers/staging/zram/zram_drv.c
> > > +++ b/drivers/staging/zram/zram_drv.c
> > > @@ -61,22 +61,22 @@ 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)
> > > @@ -96,16 +96,17 @@ 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->stats.pages_zero--;
> > > }
> > > return;
> > > @@ -114,17 +115,17 @@ static void zram_free_page(struct zram *zram, size_t index)
> > > if (unlikely(size > max_zpage_size))
> > > zram->stats.bad_compress--;
> > >
> > > - zs_free(zram->mem_pool, handle);
> > > + zs_free(meta->mem_pool, handle);
> > >
> > > if (size <= PAGE_SIZE / 2)
> > > zram->stats.good_compress--;
> > >
> > > zram_stat64_sub(zram, &zram->stats.compr_size,
> > > - zram->table[index].size);
> > > + meta->table[index].size);
> > > 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)
> > > @@ -149,20 +150,21 @@ 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)) {
> > > @@ -180,11 +182,11 @@ 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;
> > > }
> > > @@ -232,9 +234,10 @@ 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;
> >
> > Could you explain compress_buffer is used for what? Thanks for your
> > clarify!
>
> IMHO, it is used for storing compressed result in write path
> while compress_workmem is used for compression temporally.

Oh, I see, thanks. :)

>
> >
> > >
> > > if (is_partial_io(bvec)) {
> > > /*
> > > @@ -256,8 +259,8 @@ 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);
> > > @@ -276,13 +279,13 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> > > if (is_partial_io(bvec))
> > > kfree(uncmem);
> > > 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);
> > > @@ -303,14 +306,14 @@ 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);
> > > @@ -318,10 +321,10 @@ 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);
> > > @@ -464,34 +467,25 @@ error:
> > > void __zram_reset_device(struct zram *zram)
> > > {
> > > size_t index;
> > > + struct zram_meta *meta;
> > >
> > > if (!zram->init_done)
> > > return;
> > >
> > > + 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));
> > >
> > > @@ -506,12 +500,65 @@ 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)
> > > +{
> > > + 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)
> > > {
> > > - int ret;
> > > 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(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 "
> > > @@ -526,51 +573,13 @@ 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(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);
> > >
> > > #endif
> > > diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
> > > index 369db12..e6a929d 100644
> > > --- a/drivers/staging/zram/zram_sysfs.c
> > > +++ b/drivers/staging/zram/zram_sysfs.c
> > > @@ -56,22 +56,26 @@ static ssize_t disksize_store(struct device *dev,
> > > struct device_attribute *attr, const char *buf, size_t len)
> > > {
> > > u64 disksize;
> > > + struct zram_meta *meta;
> > > struct zram *zram = dev_to_zram(dev);
> > >
> > > disksize = memparse(buf, NULL);
> > > if (!disksize)
> > > return -EINVAL;
> > >
> > > + disksize = PAGE_ALIGN(disksize);
> > > + meta = zram_meta_alloc(disksize);
> > > down_write(&zram->init_lock);
> > > if (zram->init_done) {
> > > up_write(&zram->init_lock);
> > > + zram_meta_free(meta);
> > > pr_info("Cannot change disksize for initialized device\n");
> > > return -EBUSY;
> > > }
> > >
> > > - zram->disksize = PAGE_ALIGN(disksize);
> > > + zram->disksize = disksize;
> > > set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> > > - zram_init_device(zram);
> > > + zram_init_device(zram, meta);
> > > up_write(&zram->init_lock);
> > >
> > > return len;
> > > @@ -182,9 +186,10 @@ static ssize_t mem_used_total_show(struct device *dev,
> > > {
> > > u64 val = 0;
> > > struct zram *zram = dev_to_zram(dev);
> > > + struct zram_meta *meta = zram->meta;
> > >
> > > if (zram->init_done)
> > > - val = zs_get_total_size_bytes(zram->mem_pool);
> > > + val = zs_get_total_size_bytes(meta->mem_pool);
> > >
> > > return sprintf(buf, "%llu\n", val);
> > > }
> >
> >
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
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