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UPSTREAM: zram: fix broken page writeback

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commit 0d8359620d9b ("zram: support page writeback") introduced two
problems.  It overwrites writeback_store's return value as kstrtol's
return value, which makes return value zero so user could see zero as
return value of write syscall even though it wrote data successfully.

It also breaks index value in the loop in that it doesn't increase the
index any longer.  It means it can write only first starting block index
so user couldn't write all idle pages in the zram so lose memory saving
chance.

This patch fixes those issues.

Link: https://lkml.kernel.org/r/20210312173949.2197662-2-minchan@kernel.org
Fixes: 0d8359620d9b("zram: support page writeback")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Amos Bianchi <amosbianchi@google.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: John Dias <joaodias@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 2766f1821600cc7562bae2128ad0b163f744c5d9)

Bug: 182850185
Signed-off-by: Amos Bianchi <amosbianchi@google.com>
Change-Id: I9836b6350727dc4fffc1cc939647235781f0a4ee
This commit is contained in:
Minchan Kim
2021-03-12 21:08:41 -08:00
committed by Suren Baghdasaryan
parent 542d1937ba
commit e4636b47ef
1 changed files with 3 additions and 3 deletions
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6
drivers/block/zram/zram_drv.c
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@@ -648,8 +648,8 @@ static ssize_t writeback_store(struct device *dev,
if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1)) if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))
return -EINVAL; return -EINVAL;
ret = kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index); if (kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index) ||
if (ret || index >= nr_pages) index >= nr_pages)
return -EINVAL; return -EINVAL;
nr_pages = 1; nr_pages = 1;
@@ -673,7 +673,7 @@ static ssize_t writeback_store(struct device *dev,
goto release_init_lock; goto release_init_lock;
} }
while (nr_pages--) { for (; nr_pages != 0; index++, nr_pages--) {
struct bio_vec bvec; struct bio_vec bvec;
bvec.bv_page = page; bvec.bv_page = page;