From ce682a73b7447652f898ce1d1d0416a456df5416 Mon Sep 17 00:00:00 2001 From: Paul Barker Date: Tue, 19 Jan 2021 16:26:09 +0000 Subject: wic: Copy rootfs dir if fstab needs updating By default, wic updates the /etc/fstab in the rootfs to include details of additional partitions described in the selected wks file. If this modification is performed in place, other tasks which create an image file from the rootfs directory (e.g. do_image_tar and do_image_ext4) will pick up the modified fstab file which would not be appropriate for those images as they do not include the additional partitions described in the wks file. wic does undo modifications to the fstab file once it has finished creating the filesystem image, however this leaves open a race condition if one of the other tasks reads the contents of the fstab file from the rootfs directory between the point where wic modifies the fstab file and the point where wic restores the files original content. This could be solved by adding a lockfile for tasks which use the rootfs directory to ensure that no other such task is reading the rootfs directory while do_image_wic is running. This would serialize several do_image_* tasks and result in slower builds, especially for large images. Another drawback of this solution is that it is hard to selectively optimise - adding lockfiles to do_image_* tasks would result in these tasks always being serialized even if no fstab modification will take place. An alternative solution is to copy the rootfs directory when fstab needs to be modified. The code to do this in wic already exists as it is needed when including or excluding content in the rootfs. This still results in an impact on build times but the copy uses hardlinks if possible (so little data is actually copied) and we can make selective optimisations to improve things. The rootfs copy will only take place if fstab modification is required (or if it was already needed to include or exclude rootfs content). We can also follow up with further optimisations after this commit. So this second solution is chosen. Fixes [Yocto #13994] Signed-off-by: Paul Barker Signed-off-by: Richard Purdie --- scripts/lib/wic/partition.py | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'scripts/lib/wic/partition.py') diff --git a/scripts/lib/wic/partition.py b/scripts/lib/wic/partition.py index 286c7867cb..f59eceb23d 100644 --- a/scripts/lib/wic/partition.py +++ b/scripts/lib/wic/partition.py @@ -54,6 +54,7 @@ class Partition(): self.uuid = args.uuid self.fsuuid = args.fsuuid self.type = args.type + self.updated_fstab_path = None self.lineno = lineno self.source_file = "" @@ -118,11 +119,13 @@ class Partition(): return self.fixed_size if self.fixed_size else self.size def prepare(self, creator, cr_workdir, oe_builddir, rootfs_dir, - bootimg_dir, kernel_dir, native_sysroot): + bootimg_dir, kernel_dir, native_sysroot, updated_fstab_path): """ Prepare content for individual partitions, depending on partition command parameters. """ + self.updated_fstab_path = updated_fstab_path + if not self.source: if not self.size and not self.fixed_size: raise WicError("The %s partition has a size of zero. Please " -- cgit 1.2.3-korg