btrfs-progs: Allow open_ctree to return fs_info even chunk tree is corrupted

Current open_ctree_fs_info() won't return anything if chunk tree root is
corrupted.
This makes some function, like btrfs-find-root, unable to find any older
chunk tree root, even it is possible to use system_chunk_array in super
block.

And at least two users in mail list has reported such heavily chunk
corruption.
Although we have 'btrfs rescue chunk-recovery' but it's too time
consuming and sometimes not able to cope with a specific filesystem
corruption.

This patch adds a new open ctree flag,
OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR, allowing fs_info to be returned from
open_ctree_fs_info() even there is no valid tree root in it.

Also adds a new close_ctree() variant, close_ctree_fs_info() to handle
possible fs_info without any root.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ adjusted error messages ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/ctree.h b/ctree.h
index 21b0445..5ab0f4a 100644 (file)
--- a/ctree.h
+++ b/ctree.h
@@ -1029,6 +1029,7 @@ struct btrfs_fs_info {
        unsigned int quota_enabled:1;
        unsigned int suppress_check_block_errors:1;
        unsigned int ignore_fsid_mismatch:1;
+       unsigned int ignore_chunk_tree_error:1;
 
        int (*free_extent_hook)(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,

diff --git a/disk-io.c b/disk-io.c
index bd0444b..2ec62cf 100644 (file)
--- a/disk-io.c
+++ b/disk-io.c
@@ -1168,8 +1168,14 @@ int btrfs_setup_chunk_tree_and_device_map(struct btrfs_fs_info *fs_info)
                                                    btrfs_super_chunk_root(sb),
                                                    blocksize, generation);
        if (!extent_buffer_uptodate(fs_info->chunk_root->node)) {
-               fprintf(stderr, "Couldn't read chunk root\n");
-               return -EIO;
+               if (fs_info->ignore_chunk_tree_error) {
+                       warning("cannot read chunk root, continue anyway");
+                       fs_info->chunk_root = NULL;
+                       return 0;
+               } else {
+                       error("cannot read chunk root");
+                       return -EIO;
+               }
        }
 
        if (!(btrfs_super_flags(sb) & BTRFS_SUPER_FLAG_METADUMP)) {
@@ -1212,6 +1218,8 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
                fs_info->suppress_check_block_errors = 1;
        if (flags & OPEN_CTREE_IGNORE_FSID_MISMATCH)
                fs_info->ignore_fsid_mismatch = 1;
+       if (flags & OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR)
+               fs_info->ignore_chunk_tree_error = 1;
 
        ret = btrfs_scan_fs_devices(fp, path, &fs_devices, sb_bytenr,
                                    (flags & OPEN_CTREE_RECOVER_SUPER),
@@ -1260,13 +1268,18 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
        if (ret)
                goto out_chunk;
 
+       /* Chunk tree root is unable to read, return directly */
+       if (!fs_info->chunk_root)
+               return fs_info;
+
        eb = fs_info->chunk_root->node;
        read_extent_buffer(eb, fs_info->chunk_tree_uuid,
                           btrfs_header_chunk_tree_uuid(eb),
                           BTRFS_UUID_SIZE);
 
        ret = btrfs_setup_all_roots(fs_info, root_tree_bytenr, flags);
-       if (ret && !(flags & __OPEN_CTREE_RETURN_CHUNK_ROOT))
+       if (ret && !(flags & __OPEN_CTREE_RETURN_CHUNK_ROOT) &&
+           !fs_info->ignore_chunk_tree_error)
                goto out_chunk;
 
        return fs_info;
@@ -1308,6 +1321,8 @@ struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr,
 {
        struct btrfs_fs_info *info;
 
+       /* This flags may not return fs_info with any valid root */
+       BUG_ON(flags & OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR);
        info = open_ctree_fs_info(filename, sb_bytenr, 0, flags);
        if (!info)
                return NULL;
@@ -1320,6 +1335,9 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
                                 enum btrfs_open_ctree_flags flags)
 {
        struct btrfs_fs_info *info;
+
+       /* This flags may not return fs_info with any valid root */
+       BUG_ON(flags & OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR);
        info = __open_ctree_fd(fp, path, sb_bytenr, 0, flags);
        if (!info)
                return NULL;
@@ -1658,14 +1676,15 @@ int write_ctree_super(struct btrfs_trans_handle *trans,
        return ret;
 }
 
-int close_ctree(struct btrfs_root *root)
+int close_ctree_fs_info(struct btrfs_fs_info *fs_info)
 {
        int ret;
        struct btrfs_trans_handle *trans;
-       struct btrfs_fs_info *fs_info = root->fs_info;
+       struct btrfs_root *root = fs_info->tree_root;
 
        if (fs_info->last_trans_committed !=
            fs_info->generation) {
+               BUG_ON(!root);
                trans = btrfs_start_transaction(root, 1);
                btrfs_commit_transaction(trans, root);
                trans = btrfs_start_transaction(root, 1);

diff --git a/disk-io.h b/disk-io.h
index d3e3aaa..c2eb1d6 100644 (file)
--- a/disk-io.h
+++ b/disk-io.h
@@ -53,7 +53,15 @@ enum btrfs_open_ctree_flags {
         * Like split PARTIAL into SKIP_CSUM/SKIP_EXTENT
         */
 
-       OPEN_CTREE_IGNORE_FSID_MISMATCH = (1 << 10)
+       OPEN_CTREE_IGNORE_FSID_MISMATCH = (1 << 10),
+
+       /*
+        * Allow open_ctree_fs_info() to return a incomplete fs_info with
+        * system chunks from super block only.
+        * It's useful for chunk corruption case.
+        * Makes no sense for open_ctree variants returning btrfs_root.
+        */
+       OPEN_CTREE_IGNORE_CHUNK_TREE_ERROR = (1 << 11)
 };
 
 static inline u64 btrfs_sb_offset(int mirror)
@@ -101,7 +109,13 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
 struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
                                         u64 sb_bytenr, u64 root_tree_bytenr,
                                         enum btrfs_open_ctree_flags flags);
-int close_ctree(struct btrfs_root *root);
+int close_ctree_fs_info(struct btrfs_fs_info *fs_info);
+static inline int close_ctree(struct btrfs_root *root)
+{
+       BUG_ON(!root);
+       return close_ctree_fs_info(root->fs_info);
+}
+
 int write_all_supers(struct btrfs_root *root);
 int write_ctree_super(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root);