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zram: implement rw_page operation of zram
This patch implements rw_page operation for zram block device. I implemented the feature in zram and tested it. Test bed was the G2, LG electronic mobile device, whtich has msm8974 processor and 2GB memory. With a memory allocation test program consuming memory, the system generates swap. Operating time of swap_write_page() was measured. -------------------------------------------------- | | operating time | improvement | | | (20 runs average) | | -------------------------------------------------- |with patch | 1061.15 us | +2.4% | -------------------------------------------------- |without patch| 1087.35 us | | -------------------------------------------------- Each test(with paged_io,with BIO) result set shows normal distribution and has equal variance. I mean the two values are valid result to compare. I can say operation with paged I/O(without BIO) is faster 2.4% with confidence level 95%. [minchan@kernel.org: make rw_page opeartion return 0] [minchan@kernel.org: rely on the bi_end_io for zram_rw_page fails] [sergey.senozhatsky@gmail.com: code cleanup] [minchan@kernel.org: add comment] Signed-off-by: karam.lee <karam.lee@lge.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Jerome Marchand <jmarchan@redhat.com> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Nitin Gupta <ngupta@vflare.org> Cc: <seungho1.park@lge.com> Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: 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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@ -945,8 +945,52 @@ static void zram_slot_free_notify(struct block_device *bdev,
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atomic64_inc(&zram->stats.notify_free);
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}
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static int zram_rw_page(struct block_device *bdev, sector_t sector,
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struct page *page, int rw)
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{
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int offset, err;
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u32 index;
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struct zram *zram;
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struct bio_vec bv;
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zram = bdev->bd_disk->private_data;
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if (!valid_io_request(zram, sector, PAGE_SIZE)) {
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atomic64_inc(&zram->stats.invalid_io);
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return -EINVAL;
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}
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down_read(&zram->init_lock);
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if (unlikely(!init_done(zram))) {
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err = -EIO;
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goto out_unlock;
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}
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index = sector >> SECTORS_PER_PAGE_SHIFT;
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offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
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bv.bv_page = page;
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bv.bv_len = PAGE_SIZE;
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bv.bv_offset = 0;
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err = zram_bvec_rw(zram, &bv, index, offset, rw);
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out_unlock:
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up_read(&zram->init_lock);
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/*
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* If I/O fails, just return error(ie, non-zero) without
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* calling page_endio.
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* It causes resubmit the I/O with bio request by upper functions
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* of rw_page(e.g., swap_readpage, __swap_writepage) and
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* bio->bi_end_io does things to handle the error
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* (e.g., SetPageError, set_page_dirty and extra works).
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*/
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if (err == 0)
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page_endio(page, rw, 0);
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return err;
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}
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static const struct block_device_operations zram_devops = {
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.swap_slot_free_notify = zram_slot_free_notify,
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.rw_page = zram_rw_page,
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.owner = THIS_MODULE
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};
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