From: Amir Goldstein <amir73il@xxxxxxxxxxxx>
On snapshot take, after copying the pre-allocated blocks, some are
fixed to make the snapshot image appear as a valid Ext4 file system.
The has_snapshot flags is cleared from the super block as well as
the last_snapshot field and all snapshot inodes are cleared
(to appear as empty inodes).
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
---
fs/ext4/ext4.h | 2 +
fs/ext4/inode.c | 4 +-
fs/ext4/snapshot_ctl.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e76faae..198d7d4 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1839,6 +1839,8 @@ struct buffer_head *ext4_bread(handle_t *, struct inode *,
int ext4_get_block(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
+extern blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
+ struct ext4_inode_info *ei);
extern struct inode *ext4_iget(struct super_block *, unsigned long);
extern int ext4_write_inode(struct inode *, struct writeback_control *);
extern int ext4_setattr(struct dentry *, struct iattr *);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1558a7b..d703a55 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5178,8 +5178,8 @@ void ext4_get_inode_flags(struct ext4_inode_info *ei)
} while (cmpxchg(&ei->i_flags, old_fl, new_fl) != old_fl);
}
-static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
- struct ext4_inode_info *ei)
+blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
+ struct ext4_inode_info *ei)
{
blkcnt_t i_blocks ;
struct inode *inode = &(ei->vfs_inode);
diff --git a/fs/ext4/snapshot_ctl.c b/fs/ext4/snapshot_ctl.c
index 9d915a9..360581d 100644
--- a/fs/ext4/snapshot_ctl.c
+++ b/fs/ext4/snapshot_ctl.c
@@ -393,6 +393,7 @@ static int ext4_snapshot_create(struct inode *inode)
unsigned long ino;
struct ext4_iloc iloc;
ext4_fsblk_t bmap_blk = 0, imap_blk = 0, inode_blk = 0;
+ ext4_fsblk_t prev_inode_blk = 0;
ext4_fsblk_t snapshot_blocks = ext4_blocks_count(sbi->s_es);
if (active_snapshot) {
snapshot_debug(1, "failed to add snapshot because active "
@@ -540,7 +541,9 @@ static int ext4_snapshot_create(struct inode *inode)
goto out_handle;
}
- ino = inode->i_ino;
+ /* start with root inode and continue with snapshot list */
+ ino = EXT4_ROOT_INO;
+alloc_inode_blocks:
/*
* pre-allocate the following blocks in the new snapshot:
* - block and inode bitmap blocks of ino's block group
@@ -553,6 +556,11 @@ static int ext4_snapshot_create(struct inode *inode)
inode_blk = ext4_get_inode_block(sb, ino, &iloc);
+ if (!inode_blk || inode_blk == prev_inode_blk)
+ goto next_snapshot;
+
+ /* not same inode and bitmap blocks as prev snapshot */
+ prev_inode_blk = inode_blk;
bmap_blk = 0;
imap_blk = 0;
desc = ext4_get_group_desc(sb, iloc.block_group, NULL);
@@ -601,6 +609,10 @@ next_snapshot:
err = -EIO;
goto out_handle;
}
+ if (ino == EXT4_ROOT_INO) {
+ ino = inode->i_ino;
+ goto alloc_inode_blocks;
+ }
snapshot_debug(1, "snapshot (%u) created\n", inode->i_generation);
err = 0;
out_handle:
@@ -693,6 +705,10 @@ int ext4_snapshot_take(struct inode *inode)
struct inode *curr_inode;
struct ext4_iloc iloc;
struct ext4_group_desc *desc;
+ ext4_fsblk_t prev_inode_blk = 0;
+ struct ext4_inode *raw_inode;
+ blkcnt_t excluded_blocks = 0;
+ int fixing = 0;
int i;
int err = -EIO;
@@ -752,7 +768,9 @@ int ext4_snapshot_take(struct inode *inode)
goto out_unlockfs;
}
- curr_inode = inode;
+ /* start with root inode and continue with snapshot list */
+ curr_inode = sb->s_root->d_inode;
+copy_inode_blocks:
/*
* copy the following blocks to the new snapshot:
* - block and inode bitmap blocks of curr_inode block group
@@ -769,6 +787,11 @@ int ext4_snapshot_take(struct inode *inode)
err = err ? : -EIO;
goto out_unlockfs;
}
+ if (fixing)
+ goto fix_inode_copy;
+ if (iloc.bh->b_blocknr == prev_inode_blk)
+ goto next_inode;
+ prev_inode_blk = iloc.bh->b_blocknr;
brelse(bhs[COPY_BLOCK_BITMAP]);
bhs[COPY_BLOCK_BITMAP] = sb_bread(sb,
ext4_block_bitmap(sb, desc));
@@ -784,12 +807,59 @@ int ext4_snapshot_take(struct inode *inode)
goto out_unlockfs;
mask = NULL;
}
+ /* this is the copy pass */
+ goto next_inode;
+fix_inode_copy:
+ /* this is the fixing pass */
+ /* get snapshot copy of raw inode */
+ brelse(sbh);
+ sbh = ext4_getblk(NULL, inode,
+ SNAPSHOT_IBLOCK(iloc.bh->b_blocknr),
+ SNAPMAP_READ, &err);
+ if (!sbh)
+ goto out_unlockfs;
+ iloc.bh = sbh;
+ raw_inode = ext4_raw_inode(&iloc);
+ /*
+ * Snapshot inode blocks are excluded from COW bitmap,
+ * so they appear to be not allocated in the snapshot's
+ * block bitmap. If we want the snapshot image to pass
+ * fsck with no errors, we need to detach those blocks
+ * from the copy of the snapshot inode, so we fix the
+ * snapshot inodes to appear as empty regular files.
+ */
+ excluded_blocks += ext4_inode_blocks(raw_inode,
+ EXT4_I(curr_inode)) >>
+ (curr_inode->i_blkbits - 9);
+ lock_buffer(sbh);
+ ext4_isize_set(raw_inode, 0);
+ raw_inode->i_blocks_lo = 0;
+ raw_inode->i_blocks_high = 0;
+ raw_inode->i_flags &= cpu_to_le32(~EXT4_SNAPFILE_FL);
+ memset(raw_inode->i_block, 0, sizeof(raw_inode->i_block));
+ unlock_buffer(sbh);
+ mark_buffer_dirty(sbh);
+ sync_dirty_buffer(sbh);
+
+next_inode:
+ if (curr_inode->i_ino == EXT4_ROOT_INO) {
+ curr_inode = inode;
+ goto copy_inode_blocks;
+ }
/*
* copy super block to snapshot and fix it
*/
lock_buffer(es_bh);
memcpy(es_bh->b_data, sbi->s_sbh->b_data, sb->s_blocksize);
+ /* set the IS_SNAPSHOT flag to signal fsck this is a snapshot */
+ es->s_flags |= cpu_to_le32(EXT4_FLAGS_IS_SNAPSHOT);
+ /* reset snapshots list in snapshot's super block copy */
+ es->s_snapshot_inum = 0;
+ es->s_snapshot_list = 0;
+ /* fix free blocks count after clearing old snapshot inode blocks */
+ ext4_free_blocks_count_set(es, ext4_free_blocks_count(es) +
+ excluded_blocks);
set_buffer_uptodate(es_bh);
unlock_buffer(es_bh);
mark_buffer_dirty(es_bh);
--
1.7.4.1
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