GitLab

Alain reports that lab.nexedi.com backup restoration sometimes fails with error like

    ...
    # file gitlab/misc -> .../srv/backup/backup-gitlab.git/gitlab-backup.Pj0fpp/gitlab_backup/db/database.pgdump/7630.dat/7630.dat.ry main.cmd_restore: main.blob_to_file: write .../srv/backup/backup-gitlab.git/gitlab-backup.Pj0fpp/gitlab_backup/db/database.pgdump/7630.dat/7630.dat.ry: bad address

which means that write system call invoked by writefile at tail of blob_to_file returned EFAULT.

The blob_to_file function is organized approximately as this:

    blob_to_file(blob_sha1, path) {
        blob = ReadObject(blob_sha1, git.ObjectBlob)
        blob_content = blob.Data()
        writefile(path, blob_content)
    }

and getting EFAULT inside writefile means that blob_content points to
some unmapped memory.

How that could be?

The answer is that blob.Data(), as implemented by git2go, returns []byte
that points to Cgo memory owned by blob object, and t...