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ceph: fix race during filling readdir cache

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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>
This commit is contained in:
Yan, Zheng 2016-02-26 16:27:13 +08:00 committed by Ilya Dryomov
parent 89f081730c
commit af5e5eb574
1 changed files with 7 additions and 2 deletions
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9
fs/ceph/inode.c
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@ -1349,15 +1349,20 @@ static int fill_readdir_cache(struct inode *dir, struct dentry *dn,
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) &&