| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 27/93] ceph: fix race during filling readdir cache | Date | Thu, 6 Oct 2016 10:28:57 +0200 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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From: Yan, Zheng <zyan@redhat.com>
commit af5e5eb574776cdf1b756a27cc437bff257e22fe upstream.
Readdir cache uses page cache to save dentry pointers. When adding dentry pointers to middle of a page, we need to make sure the page already exists. Otherwise the beginning part of the page will be invalid pointers.
Signed-off-by: Yan, Zheng <zyan@redhat.com> Cc: Nikolay Borisov <kernel@kyup.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/ceph/inode.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/ceph/inode.c +++ b/fs/ceph/inode.c @@ -1358,15 +1358,20 @@ static int fill_readdir_cache(struct ino if (!ctl->page || pgoff != page_index(ctl->page)) { ceph_readdir_cache_release(ctl); - ctl->page = grab_cache_page(&dir->i_data, pgoff); + if (idx == 0) + ctl->page = grab_cache_page(&dir->i_data, pgoff); + else + ctl->page = find_lock_page(&dir->i_data, pgoff); if (!ctl->page) { ctl->index = -1; - return -ENOMEM; + return idx == 0 ? -ENOMEM : 0; } /* reading/filling the cache are serialized by * i_mutex, no need to use page lock */ unlock_page(ctl->page); ctl->dentries = kmap(ctl->page); + if (idx == 0) + memset(ctl->dentries, 0, PAGE_CACHE_SIZE); } if (req->r_dir_release_cnt == atomic64_read(&ci->i_release_count) &&
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