From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + mm-use-memalloc_nofs_save-in-readahead-path.patch added to -mm tree Date: Tue, 14 Apr 2020 18:18:07 -0700 Message-ID: <20200415011807.gvwfzju8V%akpm@linux-foundation.org> References: <20200412004155.1a8f4e081b4e03ef5903abb5@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:51466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392444AbgDOBSJ (ORCPT ); Tue, 14 Apr 2020 21:18:09 -0400 In-Reply-To: <20200412004155.1a8f4e081b4e03ef5903abb5@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: darrick.wong@oracle.com, dchinner@redhat.com, ebiggers@google.com, gaoxiang25@huawei.com, hch@lst.de, jaegeuk@kernel.org, jhubbard@nvidia.com, joseph.qi@linux.alibaba.com, junxiao.bi@oracle.com, mhocko@suse.com, mm-commits@vger.kernel.org, william.kucharski@oracle.com, willy@infradead.org, xiyou.wangcong@gmail.com, yuchao0@huawei.com, ziy@nvidia.com The patch titled Subject: mm: use memalloc_nofs_save in readahead path has been added to the -mm tree. Its filename is mm-use-memalloc_nofs_save-in-readahead-path.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-use-memalloc_nofs_save-in-readahead-path.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-use-memalloc_nofs_save-in-readahead-path.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: "Matthew Wilcox (Oracle)" Subject: mm: use memalloc_nofs_save in readahead path Ensure that memory allocations in the readahead path do not attempt to reclaim file-backed pages, which could lead to a deadlock. It is possible, though unlikely this is the root cause of a problem observed by Cong Wang. Link: http://lkml.kernel.org/r/20200414150233.24495-16-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reported-by: Cong Wang Suggested-by: Michal Hocko Reviewed-by: William Kucharski Cc: Chao Yu Cc: Christoph Hellwig Cc: Darrick J. Wong Cc: Dave Chinner Cc: Eric Biggers Cc: Gao Xiang Cc: Jaegeuk Kim Cc: John Hubbard Cc: Joseph Qi Cc: Junxiao Bi Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/readahead.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) --- a/mm/readahead.c~mm-use-memalloc_nofs_save-in-readahead-path +++ a/mm/readahead.c @@ -22,6 +22,7 @@ #include #include #include +#include #include "internal.h" @@ -186,6 +187,18 @@ void page_cache_readahead_unbounded(stru unsigned long i; /* + * Partway through the readahead operation, we will have added + * locked pages to the page cache, but will not yet have submitted + * them for I/O. Adding another page may need to allocate memory, + * which can trigger memory reclaim. Telling the VM we're in + * the middle of a filesystem operation will cause it to not + * touch file-backed pages, preventing a deadlock. Most (all?) + * filesystems already specify __GFP_NOFS in their mapping's + * gfp_mask, but let's be explicit here. + */ + unsigned int nofs = memalloc_nofs_save(); + + /* * Preallocate as many pages as we will need. */ for (i = 0; i < nr_to_read; i++) { @@ -229,6 +242,7 @@ void page_cache_readahead_unbounded(stru * will then handle the error. */ read_pages(&rac, &page_pool, false); + memalloc_nofs_restore(nofs); } EXPORT_SYMBOL_GPL(page_cache_readahead_unbounded); _ Patches currently in -mm which might be from willy@infradead.org are mm-move-readahead-prototypes-from-mmh.patch mm-return-void-from-various-readahead-functions.patch mm-ignore-return-value-of-readpages.patch mm-move-readahead-nr_pages-check-into-read_pages.patch mm-add-new-readahead_control-api.patch mm-use-readahead_control-to-pass-arguments.patch mm-rename-various-offset-parameters-to-index.patch mm-rename-readahead-loop-variable-to-i.patch mm-remove-page_offset-from-readahead-loop.patch mm-put-readahead-pages-in-cache-earlier.patch mm-add-readahead-address-space-operation.patch mm-move-end_index-check-out-of-readahead-loop.patch mm-add-page_cache_readahead_unbounded.patch mm-document-why-we-dont-set-pagereadahead.patch mm-use-memalloc_nofs_save-in-readahead-path.patch fs-convert-mpage_readpages-to-mpage_readahead.patch btrfs-convert-from-readpages-to-readahead.patch erofs-convert-uncompressed-files-from-readpages-to-readahead.patch erofs-convert-compressed-files-from-readpages-to-readahead.patch ext4-convert-from-readpages-to-readahead.patch ext4-pass-the-inode-to-ext4_mpage_readpages.patch f2fs-convert-from-readpages-to-readahead.patch f2fs-pass-the-inode-to-f2fs_mpage_readpages.patch fuse-convert-from-readpages-to-readahead.patch iomap-convert-from-readpages-to-readahead.patch