afs: split afs_pagecache_valid() out of afs_validate()

For the map_pages() method, we need a test that does not sleep. The page
fault handler will continue to call the fault() method where we can sleep
and do the full revalidation there.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Acked-by: David Howells <[e-mail]>
Tested-by: David Howells <[e-mail]>
Cc: Darrick J. Wong <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/afs/file.c

···
 static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff)
 {
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(vmf->vma->vm_file));
-	struct afs_file *af = vmf->vma->vm_file->private_data;
 
-	switch (afs_validate(vnode, af->key)) {
-	case 0:
+	if (afs_pagecache_valid(vnode))
 		return filemap_map_pages(vmf, start_pgoff, end_pgoff);
-	case -ENOMEM:
-		return VM_FAULT_OOM;
-	case -EINTR:
-	case -ERESTARTSYS:
-		return VM_FAULT_RETRY;
-	case -ESTALE:
-	default:
-		return VM_FAULT_SIGBUS;
-	}
+	return 0;
 }
 
 static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)

fs/afs/inode.c

···
 }
 
 /*
+ * Returns true if the pagecache is still valid.  Does not sleep.
+ */
+bool afs_pagecache_valid(struct afs_vnode *vnode)
+{
+	if (unlikely(test_bit(AFS_VNODE_DELETED, &vnode->flags))) {
+		if (vnode->netfs.inode.i_nlink)
+			clear_nlink(&vnode->netfs.inode);
+		return true;
+	}
+
+	if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags) &&
+	    afs_check_validity(vnode))
+		return true;
+
+	return false;
+}
+
+/*
  * validate a vnode/inode
  * - there are several things we need to check
  *   - parent dir data changes (rm, rmdir, rename, mkdir, create, link,
···
 	       vnode->fid.vid, vnode->fid.vnode, vnode->flags,
 	       key_serial(key));
 
-	if (unlikely(test_bit(AFS_VNODE_DELETED, &vnode->flags))) {
-		if (vnode->netfs.inode.i_nlink)
-			clear_nlink(&vnode->netfs.inode);
-		goto valid;
-	}
-
-	if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags) &&
-	    afs_check_validity(vnode))
+	if (afs_pagecache_valid(vnode))
 		goto valid;
 
 	down_write(&vnode->validate_lock);

fs/afs/internal.h

···
 extern struct inode *afs_root_iget(struct super_block *, struct key *);
 extern bool afs_check_validity(struct afs_vnode *);
 extern int afs_validate(struct afs_vnode *, struct key *);
+bool afs_pagecache_valid(struct afs_vnode *);
 extern int afs_getattr(struct mnt_idmap *idmap, const struct path *,
 		       struct kstat *, u32, unsigned int);
 extern int afs_setattr(struct mnt_idmap *idmap, struct dentry *, struct iattr *);