Ceph » Linux kernel client

Hit it again:

generic/467 73s ... - output mismatch (see /data/xfstests-dev/results//generic/467.out.bad)
    --- tests/generic/467.out    2022-04-07 21:42:10.690048179 +0800
    +++ /data/xfstests-dev/results//generic/467.out.bad    2022-07-12 16:52:45.692472984 +0800
    @@ -1,5 +1,6 @@
     QA output created by 467
     test_file_handles TEST_DIR/467-dir -dp
    +open_by_handle(/mnt/kcephfs.A/467-dir/file000002) opened an unlinked file!
     test_file_handles TEST_DIR/467-dir -rp
     test_file_handles TEST_DIR/467-dir -dkr
     test_file_handles TEST_DIR/467-dir -lr
    ...
    (Run 'diff -u /data/xfstests-dev/tests/generic/467.out /data/xfstests-dev/results//generic/467.out.bad'  to see the entire diff)
Ran: generic/467
Failures: generic/467
Failed 1 of 1 tests

Locally I have reproduced it and the root cause is that just after a file was deleted and only the unsafe reply was received, but the dentry was still held by the unlink request->r_dentry.

So later when the xfstests-dev test try to open it by using open_by_handle_at() the kernel will succeed:

182 static struct dentry *__fh_to_dentry(struct super_block *sb, u64 ino)
183 {                  
184         struct inode *inode = __lookup_inode(sb, ino);
185         int err;
186    
187         if (IS_ERR(inode))
188                 return ERR_CAST(inode);             
189         /* We need LINK caps to reliably check i_nlink */
190         err = ceph_do_getattr(inode, CEPH_CAP_LINK_SHARED, false);                                                                                 
191         if (err) {
192                 iput(inode);   
193                 return ERR_PTR(err);                
194         }
195         /* -ESTALE if inode as been unlinked and no file is open */
196         if ((inode->i_nlink == 0) && (atomic_read(&inode->i_count) == 1)) {
197                 iput(inode);   
198                 return ERR_PTR(-ESTALE);            
199         }
200         return d_obtain_alias(inode);       
201 }

To fix it we need to make sure the dentry is not unhashed.