logfs: survive logfs_buf_recover read errors

Refusing to mount beats a kernel crash.
Signed-off-by: Joern Engel <joern@logfs.org>

fs/logfs/journal.c

@@ -132,10 +132,9 @@ static int read_area(struct super_block *sb, struct logfs_je_area *a)
 
 	ofs = dev_ofs(sb, area->a_segno, area->a_written_bytes);
 	if (super->s_writesize > 1)
-		logfs_buf_recover(area, ofs, a + 1, super->s_writesize);
+		return logfs_buf_recover(area, ofs, a + 1, super->s_writesize);
 	else
-		logfs_buf_recover(area, ofs, NULL, 0);
-	return 0;
+		return logfs_buf_recover(area, ofs, NULL, 0);
 }
 
 static void *unpack(void *from, void *to)
@@ -245,7 +244,7 @@ static int read_je(struct super_block *sb, u64 ofs)
 		read_erasecount(sb, unpack(jh, scratch));
 		break;
 	case JE_AREA:
-		read_area(sb, unpack(jh, scratch));
+		err = read_area(sb, unpack(jh, scratch));
 		break;
 	case JE_OBJ_ALIAS:
 		err = logfs_load_object_aliases(sb, unpack(jh, scratch),

fs/logfs/logfs.h

@@ -598,19 +598,19 @@ void freeseg(struct super_block *sb, u32 segno);
 int logfs_init_areas(struct super_block *sb);
 void logfs_cleanup_areas(struct super_block *sb);
 int logfs_open_area(struct logfs_area *area, size_t bytes);
-void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
+int __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
 		int use_filler);
 
-static inline void logfs_buf_write(struct logfs_area *area, u64 ofs,
+static inline int logfs_buf_write(struct logfs_area *area, u64 ofs,
 		void *buf, size_t len)
 {
-	__logfs_buf_write(area, ofs, buf, len, 0);
+	return __logfs_buf_write(area, ofs, buf, len, 0);
 }
 
-static inline void logfs_buf_recover(struct logfs_area *area, u64 ofs,
+static inline int logfs_buf_recover(struct logfs_area *area, u64 ofs,
 		void *buf, size_t len)
 {
-	__logfs_buf_write(area, ofs, buf, len, 1);
+	return __logfs_buf_write(area, ofs, buf, len, 1);
 }
 
 /* super.c */

fs/logfs/segment.c

@@ -67,7 +67,7 @@ static struct page *get_mapping_page(struct super_block *sb, pgoff_t index,
 	return page;
 }
 
-void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
+int __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
 		int use_filler)
 {
 	pgoff_t index = ofs >> PAGE_SHIFT;
@@ -81,8 +81,10 @@ void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
 		copylen = min((ulong)len, PAGE_SIZE - offset);
 
 		page = get_mapping_page(area->a_sb, index, use_filler);
-		SetPageUptodate(page);
+		if (IS_ERR(page))
+			return PTR_ERR(page);
 		BUG_ON(!page); /* FIXME: reserve a pool */
+		SetPageUptodate(page);
 		memcpy(page_address(page) + offset, buf, copylen);
 		SetPagePrivate(page);
 		page_cache_release(page);
@@ -92,6 +94,7 @@ void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
 		offset = 0;
 		index++;
 	} while (len);
+	return 0;
 }
 
 static void pad_partial_page(struct logfs_area *area)