udf: Return error from udf_find_entry()

Return appropriate error from udf_find_entry() instead of just NULL.
That way we can distinguish the fact that some error happened when
looking up filename (and return error to userspace) from the fact that
we just didn't find the filename. Also update callers of
udf_find_entry() accordingly.

[JK: Improved udf_find_entry() documentation]
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/namei.c

@@ -138,6 +138,25 @@ int udf_write_fi(struct inode *inode, struct fileIdentDesc *cfi,
 	return 0;
 }
 
+/**
+ * udf_find_entry - find entry in given directory.
+ *
+ * @dir:	directory inode to search in
+ * @child:	qstr of the name
+ * @fibh:	buffer head / inode with file identifier descriptor we found
+ * @cfi:	found file identifier descriptor with given name
+ *
+ * This function searches in the directory @dir for a file name @child. When
+ * found, @fibh points to the buffer head(s) (bh is NULL for in ICB
+ * directories) containing the file identifier descriptor (FID). In that case
+ * the function returns pointer to the FID in the buffer or inode - but note
+ * that FID may be split among two buffers (blocks) so accessing it via that
+ * pointer isn't easily possible. This pointer can be used only as an iterator
+ * for other directory manipulation functions. For inspection of the FID @cfi
+ * can be used - the found FID is copied there.
+ *
+ * Returns pointer to FID, NULL when nothing found, or error code.
+ */
 static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 					    const struct qstr *child,
 					    struct udf_fileident_bh *fibh,
@@ -167,8 +186,11 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 	fibh->soffset = fibh->eoffset = f_pos & (sb->s_blocksize - 1);
 	if (dinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
 		if (inode_bmap(dir, f_pos >> sb->s_blocksize_bits, &epos,
-		    &eloc, &elen, &offset) != (EXT_RECORDED_ALLOCATED >> 30))
+		    &eloc, &elen, &offset) != (EXT_RECORDED_ALLOCATED >> 30)) {
+			fi = ERR_PTR(-EIO);
 			goto out_err;
+		}
+
 		block = udf_get_lb_pblock(sb, &eloc, offset);
 		if ((++offset << sb->s_blocksize_bits) < elen) {
 			if (dinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
@@ -179,19 +201,25 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 			offset = 0;
 
 		fibh->sbh = fibh->ebh = udf_tread(sb, block);
-		if (!fibh->sbh)
+		if (!fibh->sbh) {
+			fi = ERR_PTR(-EIO);
 			goto out_err;
+		}
 	}
 
 	fname = kmalloc(UDF_NAME_LEN, GFP_NOFS);
-	if (!fname)
+	if (!fname) {
+		fi = ERR_PTR(-ENOMEM);
 		goto out_err;
+	}
 
 	while (f_pos < size) {
 		fi = udf_fileident_read(dir, &f_pos, fibh, cfi, &epos, &eloc,
 					&elen, &offset);
-		if (!fi)
+		if (!fi) {
+			fi = ERR_PTR(-EIO);
 			goto out_err;
+		}
 
 		liu = le16_to_cpu(cfi->lengthOfImpUse);
 		lfi = cfi->lengthFileIdent;
@@ -234,12 +262,17 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 			continue;
 
 		flen = udf_get_filename(sb, nameptr, lfi, fname, UDF_NAME_LEN);
-		if (flen > 0 && udf_match(flen, fname, child->len, child->name))
+		if (flen < 0) {
+			fi = ERR_PTR(flen);
+			goto out_err;
+		}
+
+		if (udf_match(flen, fname, child->len, child->name))
 			goto out_ok;
 	}
 
-out_err:
 	fi = NULL;
+out_err:
 	if (fibh->sbh != fibh->ebh)
 		brelse(fibh->ebh);
 	brelse(fibh->sbh);
@@ -256,6 +289,7 @@ static struct dentry *udf_lookup(struct inode *dir, struct dentry *dentry,
 	struct inode *inode = NULL;
 	struct fileIdentDesc cfi;
 	struct udf_fileident_bh fibh;
+	struct fileIdentDesc *fi;
 
 	if (dentry->d_name.len > UDF_NAME_LEN - 2)
 		return ERR_PTR(-ENAMETOOLONG);
@@ -275,7 +309,11 @@ static struct dentry *udf_lookup(struct inode *dir, struct dentry *dentry,
 	} else
 #endif /* UDF_RECOVERY */
 
-	if (udf_find_entry(dir, &dentry->d_name, &fibh, &cfi)) {
+	fi = udf_find_entry(dir, &dentry->d_name, &fibh, &cfi);
+	if (IS_ERR(fi))
+		return ERR_CAST(fi);
+
+	if (fi) {
 		struct kernel_lb_addr loc;
 
 		if (fibh.sbh != fibh.ebh)
@@ -774,8 +812,11 @@ static int udf_rmdir(struct inode *dir, struct dentry *dentry)
 
 	retval = -ENOENT;
 	fi = udf_find_entry(dir, &dentry->d_name, &fibh, &cfi);
-	if (!fi)
+	if (IS_ERR_OR_NULL(fi)) {
+		if (fi)
+			retval = PTR_ERR(fi);
 		goto out;
+	}
 
 	retval = -EIO;
 	tloc = lelb_to_cpu(cfi.icb.extLocation);
@@ -817,8 +858,12 @@ static int udf_unlink(struct inode *dir, struct dentry *dentry)
 
 	retval = -ENOENT;
 	fi = udf_find_entry(dir, &dentry->d_name, &fibh, &cfi);
-	if (!fi)
+
+	if (IS_ERR_OR_NULL(fi)) {
+		if (fi)
+			retval = PTR_ERR(fi);
 		goto out;
+	}
 
 	retval = -EIO;
 	tloc = lelb_to_cpu(cfi.icb.extLocation);
@@ -1049,24 +1094,30 @@ static int udf_rename(struct inode *old_dir, struct dentry *old_dentry,
 	struct udf_inode_info *old_iinfo = UDF_I(old_inode);
 
 	ofi = udf_find_entry(old_dir, &old_dentry->d_name, &ofibh, &ocfi);
-	if (ofi) {
-		if (ofibh.sbh != ofibh.ebh)
-			brelse(ofibh.ebh);
-		brelse(ofibh.sbh);
+	if (IS_ERR(ofi)) {
+		retval = PTR_ERR(ofi);
+		goto end_rename;
 	}
+
+	if (ofibh.sbh != ofibh.ebh)
+		brelse(ofibh.ebh);
+
+	brelse(ofibh.sbh);
 	tloc = lelb_to_cpu(ocfi.icb.extLocation);
 	if (!ofi || udf_get_lb_pblock(old_dir->i_sb, &tloc, 0)
 	    != old_inode->i_ino)
 		goto end_rename;
 
 	nfi = udf_find_entry(new_dir, &new_dentry->d_name, &nfibh, &ncfi);
-	if (nfi) {
-		if (!new_inode) {
-			if (nfibh.sbh != nfibh.ebh)
-				brelse(nfibh.ebh);
-			brelse(nfibh.sbh);
-			nfi = NULL;
-		}
+	if (IS_ERR(nfi)) {
+		retval = PTR_ERR(nfi);
+		goto end_rename;
+	}
+	if (nfi && !new_inode) {
+		if (nfibh.sbh != nfibh.ebh)
+			brelse(nfibh.ebh);
+		brelse(nfibh.sbh);
+		nfi = NULL;
 	}
 	if (S_ISDIR(old_inode->i_mode)) {
 		int offset = udf_ext0_offset(old_inode);