nilfs2: introduce secondary super block

The former versions didn't have extra super blocks.  This improves the
weak point by introducing another super block at unused region in tail of
the partition.

This doesn't break disk format compatibility; older versions just ingore
the secondary super block, and new versions just recover it if it doesn't
exist.  The partition created by an old mkfs may not have unused region,
but in that case, the secondary super block will not be added.

This doesn't make more redundant copies of the super block; it is a future
work.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 156 insertions, 24 deletions

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 661ab762d765..33400cf0bbe2 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
+#include <linux/crc32.h>
 #include "nilfs.h"
 #include "segment.h"
 #include "alloc.h"
@@ -105,7 +106,8 @@ void put_nilfs(struct the_nilfs *nilfs)
 	}
 	if (nilfs_init(nilfs)) {
 		nilfs_destroy_gccache(nilfs);
-		brelse(nilfs->ns_sbh);
+		brelse(nilfs->ns_sbh[0]);
+		brelse(nilfs->ns_sbh[1]);
 	}
 	kfree(nilfs);
 }
@@ -115,6 +117,7 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 {
 	struct buffer_head *bh_sr;
 	struct nilfs_super_root *raw_sr;
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
 	unsigned dat_entry_size, segment_usage_size, checkpoint_size;
 	unsigned inode_size;
 	int err;
@@ -124,9 +127,9 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 		return err;
 
 	down_read(&nilfs->ns_sem);
-	dat_entry_size = le16_to_cpu(nilfs->ns_sbp->s_dat_entry_size);
-	checkpoint_size = le16_to_cpu(nilfs->ns_sbp->s_checkpoint_size);
-	segment_usage_size = le16_to_cpu(nilfs->ns_sbp->s_segment_usage_size);
+	dat_entry_size = le16_to_cpu(sbp[0]->s_dat_entry_size);
+	checkpoint_size = le16_to_cpu(sbp[0]->s_checkpoint_size);
+	segment_usage_size = le16_to_cpu(sbp[0]->s_segment_usage_size);
 	up_read(&nilfs->ns_sem);
 
 	inode_size = nilfs->ns_inode_size;
@@ -270,11 +273,8 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 			nilfs_mdt_destroy(nilfs->ns_dat);
 			goto failed;
 		}
-		if (ri.ri_need_recovery == NILFS_RECOVERY_SR_UPDATED) {
-			down_write(&nilfs->ns_sem);
-			nilfs_update_last_segment(sbi, 0);
-			up_write(&nilfs->ns_sem);
-		}
+		if (ri.ri_need_recovery == NILFS_RECOVERY_SR_UPDATED)
+			sbi->s_super->s_dirt = 1;
 	}
 
 	set_nilfs_loaded(nilfs);
@@ -296,9 +296,8 @@ static unsigned long long nilfs_max_size(unsigned int blkbits)
 	return res;
 }
 
-static int
-nilfs_store_disk_layout(struct the_nilfs *nilfs, struct super_block *sb,
-			struct nilfs_super_block *sbp)
+static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
+				   struct nilfs_super_block *sbp)
 {
 	if (le32_to_cpu(sbp->s_rev_level) != NILFS_CURRENT_REV) {
 		printk(KERN_ERR "NILFS: revision mismatch "
@@ -309,6 +308,10 @@ nilfs_store_disk_layout(struct the_nilfs *nilfs, struct super_block *sb,
 		       NILFS_CURRENT_REV, NILFS_MINOR_REV);
 		return -EINVAL;
 	}
+	nilfs->ns_sbsize = le16_to_cpu(sbp->s_bytes);
+	if (nilfs->ns_sbsize > BLOCK_SIZE)
+		return -EINVAL;
+
 	nilfs->ns_inode_size = le16_to_cpu(sbp->s_inode_size);
 	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);
 
@@ -330,6 +333,122 @@ nilfs_store_disk_layout(struct the_nilfs *nilfs, struct super_block *sb,
 	return 0;
 }
 
+static int nilfs_valid_sb(struct nilfs_super_block *sbp)
+{
+	static unsigned char sum[4];
+	const int sumoff = offsetof(struct nilfs_super_block, s_sum);
+	size_t bytes;
+	u32 crc;
+
+	if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
+		return 0;
+	bytes = le16_to_cpu(sbp->s_bytes);
+	if (bytes > BLOCK_SIZE)
+		return 0;
+	crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,
+		       sumoff);
+	crc = crc32_le(crc, sum, 4);
+	crc = crc32_le(crc, (unsigned char *)sbp + sumoff + 4,
+		       bytes - sumoff - 4);
+	return crc == le32_to_cpu(sbp->s_sum);
+}
+
+static int nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
+{
+	return offset < ((le64_to_cpu(sbp->s_nsegments) *
+			  le32_to_cpu(sbp->s_blocks_per_segment)) <<
+			 (le32_to_cpu(sbp->s_log_block_size) + 10));
+}
+
+static void nilfs_release_super_block(struct the_nilfs *nilfs)
+{
+	int i;
+
+	for (i = 0; i < 2; i++) {
+		if (nilfs->ns_sbp[i]) {
+			brelse(nilfs->ns_sbh[i]);
+			nilfs->ns_sbh[i] = NULL;
+			nilfs->ns_sbp[i] = NULL;
+		}
+	}
+}
+
+void nilfs_fall_back_super_block(struct the_nilfs *nilfs)
+{
+	brelse(nilfs->ns_sbh[0]);
+	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
+	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
+	nilfs->ns_sbh[1] = NULL;
+	nilfs->ns_sbp[1] = NULL;
+}
+
+void nilfs_swap_super_block(struct the_nilfs *nilfs)
+{
+	struct buffer_head *tsbh = nilfs->ns_sbh[0];
+	struct nilfs_super_block *tsbp = nilfs->ns_sbp[0];
+
+	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
+	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
+	nilfs->ns_sbh[1] = tsbh;
+	nilfs->ns_sbp[1] = tsbp;
+}
+
+static int nilfs_load_super_block(struct the_nilfs *nilfs,
+				  struct super_block *sb, int blocksize,
+				  struct nilfs_super_block **sbpp)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	struct buffer_head **sbh = nilfs->ns_sbh;
+	u64 sb2off = NILFS_SB2_OFFSET_BYTES(nilfs->ns_bdev->bd_inode->i_size);
+	int valid[2], swp = 0;
+
+	sbp[0] = nilfs_read_super_block(sb, NILFS_SB_OFFSET_BYTES, blocksize,
+					&sbh[0]);
+	sbp[1] = nilfs_read_super_block(sb, sb2off, blocksize, &sbh[1]);
+
+	if (!sbp[0]) {
+		if (!sbp[1]) {
+			printk(KERN_ERR "NILFS: unable to read superblock\n");
+			return -EIO;
+		}
+		printk(KERN_WARNING
+		       "NILFS warning: unable to read primary superblock\n");
+	} else if (!sbp[1])
+		printk(KERN_WARNING
+		       "NILFS warning: unable to read secondary superblock\n");
+
+	valid[0] = nilfs_valid_sb(sbp[0]);
+	valid[1] = nilfs_valid_sb(sbp[1]);
+	swp = valid[1] &&
+		(!valid[0] ||
+		 le64_to_cpu(sbp[1]->s_wtime) > le64_to_cpu(sbp[0]->s_wtime));
+
+	if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
+		brelse(sbh[1]);
+		sbh[1] = NULL;
+		sbp[1] = NULL;
+		swp = 0;
+	}
+	if (!valid[swp]) {
+		nilfs_release_super_block(nilfs);
+		printk(KERN_ERR "NILFS: Can't find nilfs on dev %s.\n",
+		       sb->s_id);
+		return -EINVAL;
+	}
+
+	if (swp) {
+		printk(KERN_WARNING "NILFS warning: broken superblock. "
+		       "using spare superblock.\n");
+		nilfs_swap_super_block(nilfs);
+	}
+
+	nilfs->ns_sbwtime[0] = le64_to_cpu(sbp[0]->s_wtime);
+	nilfs->ns_sbwtime[1] = valid[!swp] ? le64_to_cpu(sbp[1]->s_wtime) : 0;
+	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
+	*sbpp = sbp[0];
+	return 0;
+}
+
 /**
  * init_nilfs - initialize a NILFS instance.
  * @nilfs: the_nilfs structure
@@ -352,16 +471,15 @@ nilfs_store_disk_layout(struct the_nilfs *nilfs, struct super_block *sb,
 int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 {
 	struct super_block *sb = sbi->s_super;
-	struct buffer_head *sbh;
 	struct nilfs_super_block *sbp;
 	struct backing_dev_info *bdi;
 	int blocksize;
-	int err = 0;
+	int err;
 
 	down_write(&nilfs->ns_sem);
 	if (nilfs_init(nilfs)) {
 		/* Load values from existing the_nilfs */
-		sbp = nilfs->ns_sbp;
+		sbp = nilfs->ns_sbp[0];
 		err = nilfs_store_magic_and_option(sb, sbp, data);
 		if (err)
 			goto out;
@@ -377,36 +495,50 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 		goto out;
 	}
 
-	sbp = nilfs_load_super_block(sb, &sbh);
-	if (!sbp) {
+	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
+	if (!blocksize) {
+		printk(KERN_ERR "NILFS: unable to set blocksize\n");
 		err = -EINVAL;
 		goto out;
 	}
+	err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
+	if (err)
+		goto out;
+
 	err = nilfs_store_magic_and_option(sb, sbp, data);
 	if (err)
 		goto failed_sbh;
 
 	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
 	if (sb->s_blocksize != blocksize) {
-		sbp = nilfs_reload_super_block(sb, &sbh, blocksize);
-		if (!sbp) {
+		int hw_blocksize = bdev_hardsect_size(sb->s_bdev);
+
+		if (blocksize < hw_blocksize) {
+			printk(KERN_ERR
+			       "NILFS: blocksize %d too small for device "
+			       "(sector-size = %d).\n",
+			       blocksize, hw_blocksize);
 			err = -EINVAL;
+			goto failed_sbh;
+		}
+		nilfs_release_super_block(nilfs);
+		sb_set_blocksize(sb, blocksize);
+
+		err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
+		if (err)
 			goto out;
 			/* not failed_sbh; sbh is released automatically
 			   when reloading fails. */
-		}
 	}
 	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
 
-	err = nilfs_store_disk_layout(nilfs, sb, sbp);
+	err = nilfs_store_disk_layout(nilfs, sbp);
 	if (err)
 		goto failed_sbh;
 
 	sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
 
 	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);
-	nilfs->ns_sbh = sbh;
-	nilfs->ns_sbp = sbp;
 
 	bdi = nilfs->ns_bdev->bd_inode_backing_dev_info;
 	if (!bdi)
@@ -443,7 +575,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	return err;
 
  failed_sbh:
-	brelse(sbh);
+	nilfs_release_super_block(nilfs);
 	goto out;
 }