104 lines
3.1 KiB
Diff
104 lines
3.1 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
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Date: Fri, 23 Mar 2018 09:19:21 +0100
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Subject: [PATCH] mm/shmem: do not wait for lock_page() in
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shmem_unused_huge_shrink()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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shmem_unused_huge_shrink() gets called from reclaim path. Waiting for
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page lock may lead to deadlock there.
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There was a bug report that may be attributed to this:
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http://lkml.kernel.org/r/alpine.LRH.2.11.1801242349220.30642@mail.ewheeler.net
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Replace lock_page() with trylock_page() and skip the page if we failed to
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lock it. We will get to the page on the next scan.
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We can test for the PageTransHuge() outside the page lock as we only need
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protection against splitting the page under us. Holding pin oni the page
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is enough for this.
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Link: http://lkml.kernel.org/r/20180316210830.43738-1-kirill.shutemov@linux.intel.com
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Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure")
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Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
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Reported-by: Eric Wheeler <linux-mm@lists.ewheeler.net>
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Acked-by: Michal Hocko <mhocko@suse.com>
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Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
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Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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Cc: Hugh Dickins <hughd@google.com>
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Cc: <stable@vger.kernel.org> [4.8+]
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Signed-off-by: Andrew Morton <>
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(cherry-picked from https://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git/commit/?h=since-4.15&id=73eccc61c701ee7b4223aea2079542a712feeea7)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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mm/shmem.c | 31 ++++++++++++++++++++-----------
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1 file changed, 20 insertions(+), 11 deletions(-)
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diff --git a/mm/shmem.c b/mm/shmem.c
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index 859e4c224b80..2aae929eb90b 100644
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--- a/mm/shmem.c
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+++ b/mm/shmem.c
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@@ -483,36 +483,45 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
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info = list_entry(pos, struct shmem_inode_info, shrinklist);
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inode = &info->vfs_inode;
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- if (nr_to_split && split >= nr_to_split) {
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- iput(inode);
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- continue;
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- }
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+ if (nr_to_split && split >= nr_to_split)
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+ goto leave;
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- page = find_lock_page(inode->i_mapping,
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+ page = find_get_page(inode->i_mapping,
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(inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
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if (!page)
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goto drop;
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+ /* No huge page at the end of the file: nothing to split */
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if (!PageTransHuge(page)) {
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- unlock_page(page);
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put_page(page);
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goto drop;
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}
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+ /*
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+ * Leave the inode on the list if we failed to lock
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+ * the page at this time.
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+ *
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+ * Waiting for the lock may lead to deadlock in the
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+ * reclaim path.
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+ */
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+ if (!trylock_page(page)) {
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+ put_page(page);
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+ goto leave;
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+ }
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+
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ret = split_huge_page(page);
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unlock_page(page);
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put_page(page);
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- if (ret) {
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- /* split failed: leave it on the list */
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- iput(inode);
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- continue;
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- }
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+ /* If split failed leave the inode on the list */
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+ if (ret)
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+ goto leave;
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split++;
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drop:
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list_del_init(&info->shrinklist);
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removed++;
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+leave:
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iput(inode);
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}
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--
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2.14.2
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