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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, amosbianchi@google.com,
	joaodias@google.com, linux-mm@kvack.org, minchan@kernel.org,
	mm-commits@vger.kernel.org, sergey.senozhatsky@gmail.com,
	stable@vger.kernel.org, torvalds@linux-foundation.org
Subject: [patch 29/29] zram: fix broken page writeback
Date: Fri, 12 Mar 2021 21:08:41 -0800	[thread overview]
Message-ID: <20210313050841.HjY9UHuIF%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210312210632.9b7d62973d72a56fb13c7a03@linux-foundation.org>

From: Minchan Kim <minchan@kernel.org>
Subject: zram: fix broken page writeback

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>
---

 drivers/block/zram/zram_drv.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-fix-broken-page-writeback
+++ a/drivers/block/zram/zram_drv.c
@@ -638,8 +638,8 @@ static ssize_t writeback_store(struct de
 		if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))
 			return -EINVAL;
 
-		ret = kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index);
-		if (ret || index >= nr_pages)
+		if (kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index) ||
+				index >= nr_pages)
 			return -EINVAL;
 
 		nr_pages = 1;
@@ -663,7 +663,7 @@ static ssize_t writeback_store(struct de
 		goto release_init_lock;
 	}
 
-	while (nr_pages--) {
+	for (; nr_pages != 0; index++, nr_pages--) {
 		struct bio_vec bvec;
 
 		bvec.bv_page = page;
_

      parent reply	other threads:[~2021-03-13  5:09 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-13  5:06 incoming Andrew Morton
2021-03-13  5:07 ` [patch 01/29] memblock: fix section mismatch warning Andrew Morton
2021-03-13  5:07 ` [patch 02/29] stop_machine: mark helpers __always_inline Andrew Morton
2021-03-13  5:07 ` [patch 03/29] init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM Andrew Morton
2021-03-13  5:07 ` [patch 04/29] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout Andrew Morton
2021-03-13  5:07 ` [patch 05/29] mm/fork: clear PASID for new mm Andrew Morton
2021-03-13  5:07 ` [patch 06/29] hugetlb: dedup the code to add a new file_region Andrew Morton
2021-03-13  5:07 ` [patch 07/29] hugetlb: break earlier in add_reservation_in_range() when we can Andrew Morton
2021-03-13  5:07 ` [patch 08/29] mm: introduce page_needs_cow_for_dma() for deciding whether cow Andrew Morton
2021-03-13  5:07 ` [patch 09/29] mm: use is_cow_mapping() across tree where proper Andrew Morton
2021-03-13  5:07 ` [patch 10/29] hugetlb: do early cow when page pinned on src mm Andrew Morton
2021-03-13  5:07 ` [patch 11/29] mm/highmem.c: fix zero_user_segments() with start > end Andrew Morton
2021-03-13  5:07 ` [patch 12/29] binfmt_misc: fix possible deadlock in bm_register_write Andrew Morton
2021-03-13  5:07 ` [patch 13/29] MAINTAINERS: exclude uapi directories in API/ABI section Andrew Morton
2021-03-13  5:07 ` [patch 14/29] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP* Andrew Morton
2021-03-13  5:07 ` [patch 15/29] kfence: fix printk format for ptrdiff_t Andrew Morton
2021-03-13  5:07 ` [patch 16/29] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations Andrew Morton
2021-03-13  5:08 ` [patch 17/29] kfence: fix reports if constant function prefixes exist Andrew Morton
2021-03-13  5:08 ` [patch 18/29] include/linux/sched/mm.h: use rcu_dereference in in_vfork() Andrew Morton
2021-03-13  5:08 ` [patch 19/29] mm/madvise: replace ptrace attach requirement for process_madvise Andrew Morton
2021-03-13  5:08 ` [patch 20/29] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC Andrew Morton
2021-03-13  5:08 ` [patch 21/29] kasan: fix KASAN_STACK dependency for HW_TAGS Andrew Morton
2021-03-13  5:08 ` [patch 22/29] mm/userfaultfd: fix memory corruption due to writeprotect Andrew Morton
2021-03-13  5:08 ` [patch 23/29] mm, hwpoison: do not lock page again when me_huge_page() successfully recovers Andrew Morton
2021-03-13 19:23   ` Linus Torvalds
2021-03-14  6:36     ` HORIGUCHI NAOYA(堀口　直也)
2021-03-13  5:08 ` [patch 24/29] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls Andrew Morton
2021-03-13  5:08 ` [patch 25/29] ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign Andrew Morton
2021-03-13  5:08 ` [patch 26/29] mm/memcg: rename mem_cgroup_split_huge_fixup to split_page_memcg and add nr_pages argument Andrew Morton
2021-03-13  5:08 ` [patch 27/29] mm/memcg: set memcg when splitting page Andrew Morton
2021-03-13  5:08 ` [patch 28/29] zram: fix return value on writeback_store Andrew Morton
2021-03-13  5:08 ` Andrew Morton [this message]

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