afs: Fix silly rename

Fix AFS's silly rename by the following means:

 (1) Set the destination directory in afs_do_silly_rename() so as to avoid
     misbehaviour and indicate that the directory data version will
     increment by 1 so as to avoid warnings about unexpected changes in the
     DV.  Also indicate that the ctime should be updated to avoid xfstest
     grumbling.

 (2) Note when the server indicates that a directory changed more than we
     expected (AFS_OPERATION_DIR_CONFLICT), indicating a conflict with a
     third party change, checking on successful completion of unlink and
     rename.

     The problem is that the FS.RemoveFile RPC op doesn't report the status
     of the unlinked file, though YFS.RemoveFile2 does.  This can be
     mitigated by the assumption that if the directory DV cranked by
     exactly 1, we can be sure we removed one link from the file; further,
     ordinarily in AFS, files cannot be hardlinked across directories, so
     if we reduce nlink to 0, the file is deleted.

     However, if the directory DV jumps by more than 1, we cannot know if a
     third party intervened by adding or removing a link on the file we
     just removed a link from.

     The same also goes for any vnode that is at the destination of the
     FS.Rename RPC op.

 (3) Make afs_vnode_commit_status() apply the nlink drop inside the cb_lock
     section along with the other attribute updates if ->op_unlinked is set
     on the descriptor for the appropriate vnode.

 (4) Issue a follow up status fetch to the unlinked file in the event of a
     third party conflict that makes it impossible for us to know if we
     actually deleted the file or not.

 (5) Provide a flag, AFS_VNODE_SILLY_DELETED, to make afs_getattr() lie to
     the user about the nlink of a silly deleted file so that it appears as
     0, not 1.

Found with the generic/035 and generic/084 xfstests.

Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 9420890e3577..573a5922c3bb 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -634,6 +634,7 @@ struct afs_vnode {
 #define AFS_VNODE_AUTOCELL	6		/* set if Vnode is an auto mount point */
 #define AFS_VNODE_PSEUDODIR	7 		/* set if Vnode is a pseudo directory */
 #define AFS_VNODE_NEW_CONTENT	8		/* Set if file has new content (create/trunc-0) */
+#define AFS_VNODE_SILLY_DELETED	9		/* Set if file has been silly-deleted */
 
 	struct list_head	wb_keys;	/* List of keys available for writeback */
 	struct list_head	pending_locks;	/* locks waiting to be granted */
@@ -748,6 +749,7 @@ struct afs_vnode_param {
 	bool			need_io_lock:1;	/* T if we need the I/O lock on this */
 	bool			update_ctime:1;	/* Need to update the ctime */
 	bool			set_size:1;	/* Must update i_size */
+	bool			op_unlinked:1;	/* True if file was unlinked by op */
 };
 
 /*
@@ -839,6 +841,7 @@ struct afs_operation {
 #define AFS_OPERATION_LOCK_1		0x0200	/* Set if have io_lock on file[1] */
 #define AFS_OPERATION_TRIED_ALL		0x0400	/* Set if we've tried all the fileservers */
 #define AFS_OPERATION_RETRY_SERVER	0x0800	/* Set if we should retry the current server */
+#define AFS_OPERATION_DIR_CONFLICT	0x1000	/* Set if we detected a 3rd-party dir change */
 };
 
 /*
@@ -1066,6 +1069,8 @@ extern int afs_wait_for_one_fs_probe(struct afs_server *, bool);
 /*
  * inode.c
  */
+extern const struct afs_operation_ops afs_fetch_status_operation;
+
 extern void afs_vnode_commit_status(struct afs_operation *, struct afs_vnode_param *);
 extern int afs_fetch_status(struct afs_vnode *, struct key *, bool, afs_access_t *);
 extern int afs_ilookup5_test_by_fid(struct inode *, void *);
@@ -1497,6 +1502,18 @@ static inline void afs_update_dentry_version(struct afs_operation *op,
 			(void *)(unsigned long)dir_vp->scb.status.data_version;
 }
 
+/*
+ * Check for a conflicting operation on a directory that we just unlinked from.
+ * If someone managed to sneak a link or an unlink in on the file we just
+ * unlinked, we won't be able to trust nlink on an AFS file (but not YFS).
+ */
+static inline void afs_check_dir_conflict(struct afs_operation *op,
+					  struct afs_vnode_param *dvp)
+{
+	if (dvp->dv_before + dvp->dv_delta != dvp->scb.status.data_version)
+		op->flags |= AFS_OPERATION_DIR_CONFLICT;
+}
+
 static inline int afs_io_error(struct afs_call *call, enum afs_io_error where)
 {
 	trace_afs_io_error(call->debug_id, -EIO, where);