zram: write incompressible pages to backing device
This patch enables write IO to transfer data to backing device. For that, it implements write_to_bdev function which creates new bio and chaining with parent bio to make the parent bio asynchrnous. For rw_page which don't have parent bio, it submit owned bio and handle IO completion by zram_page_end_io. Also, this patch defines new flag ZRAM_WB to mark written page for later read IO. [xieyisheng1@huawei.com: fix typo in comment] Link: http://lkml.kernel.org/r/1502707447-6944-2-git-send-email-xieyisheng1@huawei.com Link: http://lkml.kernel.org/r/1498459987-24562-8-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com> Cc: Juneho Choi <juno.choi@lge.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -445,9 +445,76 @@ static void put_entry_bdev(struct zram *zram, unsigned long entry)
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WARN_ON_ONCE(!was_set);
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}
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void zram_page_end_io(struct bio *bio)
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{
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struct page *page = bio->bi_io_vec[0].bv_page;
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page_endio(page, op_is_write(bio_op(bio)),
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blk_status_to_errno(bio->bi_status));
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bio_put(bio);
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}
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static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
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u32 index, struct bio *parent,
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unsigned long *pentry)
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{
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struct bio *bio;
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unsigned long entry;
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bio = bio_alloc(GFP_ATOMIC, 1);
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if (!bio)
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return -ENOMEM;
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entry = get_entry_bdev(zram);
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if (!entry) {
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bio_put(bio);
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return -ENOSPC;
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}
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bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
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bio->bi_bdev = zram->bdev;
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if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len,
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bvec->bv_offset)) {
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bio_put(bio);
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put_entry_bdev(zram, entry);
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return -EIO;
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}
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if (!parent) {
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bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
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bio->bi_end_io = zram_page_end_io;
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} else {
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bio->bi_opf = parent->bi_opf;
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bio_chain(bio, parent);
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}
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submit_bio(bio);
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*pentry = entry;
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return 0;
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}
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static void zram_wb_clear(struct zram *zram, u32 index)
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{
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unsigned long entry;
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zram_clear_flag(zram, index, ZRAM_WB);
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entry = zram_get_element(zram, index);
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zram_set_element(zram, index, 0);
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put_entry_bdev(zram, entry);
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}
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#else
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static bool zram_wb_enabled(struct zram *zram) { return false; }
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static inline void reset_bdev(struct zram *zram) {};
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static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
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u32 index, struct bio *parent,
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unsigned long *pentry)
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{
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return -EIO;
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}
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static void zram_wb_clear(struct zram *zram, u32 index) {}
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#endif
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@ -672,7 +739,13 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
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*/
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static void zram_free_page(struct zram *zram, size_t index)
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{
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unsigned long handle = zram_get_handle(zram, index);
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unsigned long handle;
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if (zram_wb_enabled(zram) && zram_test_flag(zram, index, ZRAM_WB)) {
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zram_wb_clear(zram, index);
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atomic64_dec(&zram->stats.pages_stored);
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return;
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}
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/*
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* No memory is allocated for same element filled pages.
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@ -686,6 +759,7 @@ static void zram_free_page(struct zram *zram, size_t index)
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return;
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}
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handle = zram_get_handle(zram, index);
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if (!handle)
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return;
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@ -770,7 +844,8 @@ out:
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return ret;
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}
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static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
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static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
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u32 index, struct bio *bio)
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{
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int ret = 0;
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unsigned long alloced_pages;
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@ -781,6 +856,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
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struct page *page = bvec->bv_page;
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unsigned long element = 0;
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enum zram_pageflags flags = 0;
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bool allow_wb = true;
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mem = kmap_atomic(page);
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if (page_same_filled(mem, &element)) {
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@ -805,8 +881,20 @@ compress_again:
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return ret;
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}
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if (unlikely(comp_len > max_zpage_size))
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if (unlikely(comp_len > max_zpage_size)) {
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if (zram_wb_enabled(zram) && allow_wb) {
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zcomp_stream_put(zram->comp);
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ret = write_to_bdev(zram, bvec, index, bio, &element);
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if (!ret) {
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flags = ZRAM_WB;
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ret = 1;
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goto out;
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}
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allow_wb = false;
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goto compress_again;
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}
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comp_len = PAGE_SIZE;
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}
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/*
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* handle allocation has 2 paths:
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@ -866,10 +954,11 @@ out:
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*/
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zram_slot_lock(zram, index);
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zram_free_page(zram, index);
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if (flags == ZRAM_SAME) {
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zram_set_flag(zram, index, ZRAM_SAME);
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if (flags) {
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zram_set_flag(zram, index, flags);
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zram_set_element(zram, index, element);
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} else {
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} else {
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zram_set_handle(zram, index, handle);
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zram_set_obj_size(zram, index, comp_len);
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}
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@ -881,7 +970,7 @@ out:
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}
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static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
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u32 index, int offset)
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u32 index, int offset, struct bio *bio)
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{
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int ret;
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struct page *page = NULL;
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@ -914,7 +1003,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
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vec.bv_offset = 0;
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}
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ret = __zram_bvec_write(zram, &vec, index);
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ret = __zram_bvec_write(zram, &vec, index, bio);
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out:
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if (is_partial_io(bvec))
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__free_page(page);
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@ -965,7 +1054,7 @@ static void zram_bio_discard(struct zram *zram, u32 index,
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* Returns 1 if IO request was successfully submitted.
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*/
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static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
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int offset, bool is_write)
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int offset, bool is_write, struct bio *bio)
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{
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unsigned long start_time = jiffies;
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int rw_acct = is_write ? REQ_OP_WRITE : REQ_OP_READ;
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@ -980,7 +1069,7 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
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flush_dcache_page(bvec->bv_page);
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} else {
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atomic64_inc(&zram->stats.num_writes);
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ret = zram_bvec_write(zram, bvec, index, offset);
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ret = zram_bvec_write(zram, bvec, index, offset, bio);
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}
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generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
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@ -1024,7 +1113,7 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
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bv.bv_len = min_t(unsigned int, PAGE_SIZE - offset,
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unwritten);
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if (zram_bvec_rw(zram, &bv, index, offset,
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op_is_write(bio_op(bio))) < 0)
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op_is_write(bio_op(bio)), bio) < 0)
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goto out;
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bv.bv_offset += bv.bv_len;
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@ -1098,7 +1187,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
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bv.bv_len = PAGE_SIZE;
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bv.bv_offset = 0;
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ret = zram_bvec_rw(zram, &bv, index, offset, is_write);
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ret = zram_bvec_rw(zram, &bv, index, offset, is_write, NULL);
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out:
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/*
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* If I/O fails, just return error(ie, non-zero) without
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@ -60,9 +60,10 @@ static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
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/* Flags for zram pages (table[page_no].value) */
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enum zram_pageflags {
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/* Page consists entirely of zeros */
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/* Page consists the same element */
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ZRAM_SAME = ZRAM_FLAG_SHIFT,
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ZRAM_ACCESS, /* page is now accessed */
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ZRAM_WB, /* page is stored on backing_device */
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__NR_ZRAM_PAGEFLAGS,
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};
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