Re: + zram-factor-out-partial-io-routine.patch added to -mm tree

From: Minchan Kim
Date: Mon Apr 03 2017 - 01:13:07 EST

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Hi Andrew,

Could you drop this patchset because I will send new patchset to replace
this.

Thanks.

On Wed, Mar 29, 2017 at 03:25:32PM -0700, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
>
> The patch titled
> Subject: zram: factor out partial IO routine
> has been added to the -mm tree. Its filename is
> zram-factor-out-partial-io-routine.patch
>
> This patch should soon appear at
> http://ozlabs.org/~akpm/mmots/broken-out/zram-factor-out-partial-io-routine.patch
> and later at
> http://ozlabs.org/~akpm/mmotm/broken-out/zram-factor-out-partial-io-routine.patch
>
> Before you just go and hit "reply", please:
> a) Consider who else should be cc'ed
> b) Prefer to cc a suitable mailing list as well
> c) Ideally: find the original patch on the mailing list and do a
> reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
>
> ------------------------------------------------------
> From: Minchan Kim <minchan@xxxxxxxxxx>
> Subject: zram: factor out partial IO routine
>
> For architecture(PAGE_SIZE > 4K), zram have supported partial IO.
> However, the mixed code for handling normal/partial IO is too messy,
> 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.
>
> Link: http://lkml.kernel.org/r/1490773683-10701-1-git-send-email-minchan@xxxxxxxxxx
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> drivers/block/zram/zram_drv.c | 259 ++++++++++++++++++++++----------
> 1 file changed, 186 insertions(+), 73 deletions(-)
>
> diff -puN drivers/block/zram/zram_drv.c~zram-factor-out-partial-io-routine drivers/block/zram/zram_drv.c
> --- a/drivers/block/zram/zram_drv.c~zram-factor-out-partial-io-routine
> +++ a/drivers/block/zram/zram_drv.c
> @@ -98,10 +98,17 @@ static void zram_set_obj_size(struct zra
> 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)
> {
> @@ -544,8 +551,8 @@ static int zram_decompress_page(struct z
> 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;
> @@ -562,81 +569,87 @@ static int zram_bvec_read(struct zram *z
> }
> 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);
> @@ -651,13 +664,8 @@ compress_again:
>
> 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;
> }
> @@ -665,8 +673,7 @@ compress_again:
> src = zstrm->buffer;
> if (unlikely(clen > max_zpage_size)) {
> clen = PAGE_SIZE;
> - if (is_partial_io(bvec))
> - src = uncmem;
> + src = uncmem;
> }
>
> /*
> @@ -690,8 +697,6 @@ compress_again:
> __GFP_MOVABLE);
> if (!handle) {
> zcomp_stream_put(zram->comp);
> - zstrm = NULL;
> -
> atomic64_inc(&zram->stats.writestall);
>
> handle = zs_malloc(meta->mem_pool, clen,
> @@ -702,7 +707,6 @@ compress_again:
>
> pr_err("Error allocating memory for compressed page: %u, size=%u\n",
> index, clen);
> - ret = -ENOMEM;
> goto out;
> }
>
> @@ -711,22 +715,131 @@ compress_again:
>
> 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);
>
> /*
> @@ -735,7 +848,6 @@ 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);
> bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> @@ -743,12 +855,7 @@ compress_again:
> /* 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;
> }
>
> /*
> @@ -802,10 +909,16 @@ static int zram_bvec_rw(struct zram *zra
>
> 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);
> _
>
> Patches currently in -mm which might be from minchan@xxxxxxxxxx are
>
> mm-reclaim-madv_free-pages-fix.patch
> mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one.patch
> mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one-fix.patch
> mm-do-not-use-double-negation-for-testing-page-flags.patch
> mm-remove-unncessary-ret-in-page_referenced.patch
> mm-remove-swap_dirty-in-ttu.patch
> mm-remove-swap_mlock-check-for-swap_success-in-ttu.patch
> mm-make-the-try_to_munlock-void-function.patch
> mm-remove-swap_mlock-in-ttu.patch
> mm-remove-swap_again-in-ttu.patch
> mm-make-ttus-return-boolean.patch
> mm-make-rmap_walk-void-function.patch
> mm-make-rmap_one-boolean-function.patch
> mm-remove-swap_.patch
> mm-remove-swap_-fix.patch
> zram-factor-out-partial-io-routine.patch
>
> --
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Previous message: Minchan Kim: "Re: [PATCH] zram: set physical queue limits to avoid array out of bounds accesses"
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