fs: Create a common fs_devread for ext4/reiserfs/zfs

The ext4, reiserfs and zfs filesystems all have their own implementation
of the same function, *_devread. Generalize this function into fs_devread
and put the code into fs/fs_internal.c.

Signed-off-by: Marek Behun <marek.behun@nic.cz>
[trini: Move fs/fs_internal.o hunk to the end of fs/Makefile as all
cases need it]
Signed-off-by: Tom Rini <trini@konsulko.com>

fs/fs_internal.c

@@ -0,0 +1,92 @@
+/*
+ * 2017 by Marek Behun <marek.behun@nic.cz>
+ *
+ * Derived from code in ext4/dev.c, which was based on reiserfs/dev.c
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#include <common.h>
+#include <compiler.h>
+#include <part.h>
+#include <memalign.h>
+
+int fs_devread(struct blk_desc *blk, disk_partition_t *partition,
+	       lbaint_t sector, int byte_offset, int byte_len, char *buf)
+{
+	unsigned block_len;
+	int log2blksz = blk->log2blksz;
+	ALLOC_CACHE_ALIGN_BUFFER(char, sec_buf, (blk ? blk->blksz : 0));
+	if (blk == NULL) {
+		printf("** Invalid Block Device Descriptor (NULL)\n");
+		return 0;
+	}
+
+	/* Check partition boundaries */
+	if ((sector + ((byte_offset + byte_len - 1) >> log2blksz))
+	    >= partition->size) {
+		printf("%s read outside partition " LBAFU "\n", __func__,
+		       sector);
+		return 0;
+	}
+
+	/* Get the read to the beginning of a partition */
+	sector += byte_offset >> log2blksz;
+	byte_offset &= blk->blksz - 1;
+
+	debug(" <" LBAFU ", %d, %d>\n", sector, byte_offset, byte_len);
+
+	if (byte_offset != 0) {
+		int readlen;
+		/* read first part which isn't aligned with start of sector */
+		if (blk_dread(blk, partition->start + sector, 1,
+			      (void *)sec_buf) != 1) {
+			printf(" ** %s read error **\n", __func__);
+			return 0;
+		}
+		readlen = min((int)blk->blksz - byte_offset,
+			      byte_len);
+		memcpy(buf, sec_buf + byte_offset, readlen);
+		buf += readlen;
+		byte_len -= readlen;
+		sector++;
+	}
+
+	if (byte_len == 0)
+		return 1;
+
+	/* read sector aligned part */
+	block_len = byte_len & ~(blk->blksz - 1);
+
+	if (block_len == 0) {
+		ALLOC_CACHE_ALIGN_BUFFER(u8, p, blk->blksz);
+
+		block_len = blk->blksz;
+		blk_dread(blk, partition->start + sector, 1,
+			  (void *)p);
+		memcpy(buf, p, byte_len);
+		return 1;
+	}
+
+	if (blk_dread(blk, partition->start + sector,
+		      block_len >> log2blksz, (void *)buf) !=
+			block_len >> log2blksz) {
+		printf(" ** %s read error - block\n", __func__);
+		return 0;
+	}
+	block_len = byte_len & ~(blk->blksz - 1);
+	buf += block_len;
+	byte_len -= block_len;
+	sector += block_len / blk->blksz;
+
+	if (byte_len != 0) {
+		/* read rest of data which are not in whole sector */
+		if (blk_dread(blk, partition->start + sector, 1,
+			      (void *)sec_buf) != 1) {
+			printf("* %s read error - last part\n", __func__);
+			return 0;
+		}
+		memcpy(buf, sec_buf, byte_len);
+	}
+	return 1;
+}