erofs-utils: tar: support ddtaridx format informally

`ddtaridx` is a customized tar meta-only format implemented in
Alibaba's OverlayBD project [1].

Please don't use it externally if you have no idea of this except for
the OverlayBD project.  It will be removed if some better way exists.

[1] https://github.com/containerd/overlaybd

Cc: Yifan Yuan <tuji.yyf@alibaba-inc.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240713064028.4134602-1-hsiangkao@linux.alibaba.com

diff --git a/include/erofs/tar.h b/include/erofs/tar.h
index 403f3a8271c9832d17e4c06facdebcf95931ab22..6fa72eb3ad273222d10fa03d509190fac2c118ce 100644 (file)
--- a/include/erofs/tar.h
+++ b/include/erofs/tar.h
@@ -61,6 +61,7 @@ struct erofs_tarfile {
        int fd;
        u64 offset;
        bool index_mode, headeronly_mode, rvsp_mode, aufs;
+       bool ddtaridx_mode;
 };
 
 void erofs_iostream_close(struct erofs_iostream *ios);

diff --git a/lib/tar.c b/lib/tar.c
index 5e2c5b82a9173a34e3358ce02527da78a986900a..cefda3750edaa9a480ebad36649f0001e4d3b90b 100644 (file)
--- a/lib/tar.c
+++ b/lib/tar.c
@@ -611,19 +611,6 @@ static int tarerofs_write_file_data(struct erofs_inode *inode,
        return 0;
 }
 
-static int tarerofs_write_file_index(struct erofs_inode *inode,
-               struct erofs_tarfile *tar, erofs_off_t data_offset)
-{
-       int ret;
-
-       ret = tarerofs_write_chunkes(inode, data_offset);
-       if (ret)
-               return ret;
-       if (erofs_iostream_lskip(&tar->ios, inode->i_size))
-               return -EIO;
-       return 0;
-}
-
 int tarerofs_parse_tar(struct erofs_inode *root, struct erofs_tarfile *tar)
 {
        char path[PATH_MAX];
@@ -631,7 +618,7 @@ int tarerofs_parse_tar(struct erofs_inode *root, struct erofs_tarfile *tar)
        struct erofs_sb_info *sbi = root->sbi;
        bool whout, opq, e = false;
        struct stat st;
-       erofs_off_t tar_offset, data_offset;
+       erofs_off_t tar_offset, dataoff;
 
        struct tar_header *th;
        struct erofs_dentry *d;
@@ -658,6 +645,10 @@ restart:
        tar_offset = tar->offset;
        ret = erofs_iostream_read(&tar->ios, (void **)&th, sizeof(*th));
        if (ret != sizeof(*th)) {
+               if (tar->headeronly_mode || tar->ddtaridx_mode) {
+                       ret = 1;
+                       goto out;
+               }
                erofs_err("failed to read header block @ %llu", tar_offset);
                ret = -EIO;
                goto out;
@@ -691,7 +682,7 @@ restart:
                cksum += (unsigned int)((u8*)th)[j];
                ckksum += (int)((char*)th)[j];
        }
-       if (csum != cksum && csum != ckksum) {
+       if (!tar->ddtaridx_mode && csum != cksum && csum != ckksum) {
                erofs_err("chksum mismatch @ %llu", tar_offset);
                ret = -EBADMSG;
                goto out;
@@ -770,8 +761,9 @@ restart:
                        path[--j] = '\0';
        }
 
-       data_offset = tar->offset;
-       tar->offset += st.st_size;
+       dataoff = tar->offset;
+       if (!(tar->headeronly_mode || tar->ddtaridx_mode))
+               tar->offset += st.st_size;
        switch(th->typeflag) {
        case '0':
        case '7':
@@ -860,7 +852,7 @@ restart:
 
        /* EROFS metadata index referring to the original tar data */
        if (tar->index_mode && sbi->extra_devices &&
-           erofs_blkoff(sbi, data_offset)) {
+           erofs_blkoff(sbi, dataoff)) {
                erofs_err("invalid tar data alignment @ %llu", tar_offset);
                ret = -EIO;
                goto out;
@@ -985,16 +977,27 @@ new_inode:
                } else if (inode->i_size) {
                        if (tar->headeronly_mode) {
                                ret = erofs_write_zero_inode(inode);
+                       } else if (tar->ddtaridx_mode) {
+                               dataoff = le64_to_cpu(*(__le64 *)(th->devmajor));
+                               if (tar->rvsp_mode) {
+                                       inode->datasource = EROFS_INODE_DATA_SOURCE_RESVSP;
+                                       inode->i_ino[1] = dataoff;
+                                       ret = 0;
+                               } else {
+                                       ret = tarerofs_write_chunkes(inode, dataoff);
+                               }
                        } else if (tar->rvsp_mode) {
                                inode->datasource = EROFS_INODE_DATA_SOURCE_RESVSP;
-                               inode->i_ino[1] = data_offset;
+                               inode->i_ino[1] = dataoff;
                                if (erofs_iostream_lskip(&tar->ios, inode->i_size))
                                        ret = -EIO;
                                else
                                        ret = 0;
                        } else if (tar->index_mode) {
-                               ret = tarerofs_write_file_index(inode, tar,
-                                                               data_offset);
+                               ret = tarerofs_write_chunkes(inode, dataoff);
+                               if (!ret && erofs_iostream_lskip(&tar->ios,
+                                                                inode->i_size))
+                                       ret = -EIO;
                        } else {
                                ret = tarerofs_write_file_data(inode, tar);
                        }