From 85188b767924b3a92f7d1214db7f0910513f8f5d Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 23 Mar 2021 12:01:04 +0000 Subject: [PATCH] btrfs: fix raid6 qstripe kmap MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from stable-5.10.22 commit b2a48761321893e07721d8a2528c6db0b8ac75bf bugzilla: 50796 -------------------------------- commit d70cef0d46729808dc53f145372c02b145c92604 upstream. When a qstripe is required an extra page is allocated and mapped. There were 3 problems: 1) There is no corresponding call of kunmap() for the qstripe page. 2) There is no reason to map the qstripe page more than once if the number of bits set in rbio->dbitmap is greater than one. 3) There is no reason to map the parity page and unmap it each time through the loop. The page memory can continue to be reused with a single mapping on each iteration by raid6_call.gen_syndrome() without remapping. So map the page for the duration of the loop. Similarly, improve the algorithm by mapping the parity page just 1 time. Fixes: 5a6ac9eacb49 ("Btrfs, raid56: support parity scrub on raid56") CC: stable@vger.kernel.org # 4.4.x: c17af96554a8: btrfs: raid56: simplify tracking of Q stripe presence CC: stable@vger.kernel.org # 4.4.x Signed-off-by: Ira Weiny Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Acked-by:  Weilong Chen Signed-off-by: Zheng Zengkai --- fs/btrfs/raid56.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c index 255490f42b5d..9d33bf0154ab 100644 --- a/fs/btrfs/raid56.c +++ b/fs/btrfs/raid56.c @@ -2363,16 +2363,21 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio, SetPageUptodate(p_page); if (has_qstripe) { + /* RAID6, allocate and map temp space for the Q stripe */ q_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM); if (!q_page) { __free_page(p_page); goto cleanup; } SetPageUptodate(q_page); + pointers[rbio->real_stripes - 1] = kmap(q_page); } atomic_set(&rbio->error, 0); + /* Map the parity stripe just once */ + pointers[nr_data] = kmap(p_page); + for_each_set_bit(pagenr, rbio->dbitmap, rbio->stripe_npages) { struct page *p; void *parity; @@ -2382,16 +2387,8 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio, pointers[stripe] = kmap(p); } - /* then add the parity stripe */ - pointers[stripe++] = kmap(p_page); - if (has_qstripe) { - /* - * raid6, add the qstripe and call the - * library function to fill in our p/q - */ - pointers[stripe++] = kmap(q_page); - + /* RAID6, call the library function to fill in our P/Q */ raid6_call.gen_syndrome(rbio->real_stripes, PAGE_SIZE, pointers); } else { @@ -2412,12 +2409,14 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio, for (stripe = 0; stripe < nr_data; stripe++) kunmap(page_in_rbio(rbio, stripe, pagenr, 0)); - kunmap(p_page); } + kunmap(p_page); __free_page(p_page); - if (q_page) + if (q_page) { + kunmap(q_page); __free_page(q_page); + } writeback: /* -- GitLab