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[BUG] When a scrub failed immediately without any byte scrubbed, the returned btrfs_scrub_progress::last_physical will always be 0, even if there is a non-zero @start passed into btrfs_scrub_dev() for resume cases. This will reset the progress and make later scrub resume start from the beginning. [CAUSE] The function btrfs_scrub_dev() accepts a @progress parameter to copy its updated progress to the caller, there are cases where we either don't touch progress::last_physical at all or copy 0 into last_physical: - last_physical not updated at all If some error happened before scrubbing any super block or chunk, we will not copy the progress, leaving the @last_physical untouched. E.g. failed to allocate @sctx, scrubbing a missing device or even there is already a running scrub and so on. All those cases won't touch @progress at all, resulting the last_physical untouched and will be left as 0 for most cases. - Error out before scrubbing any bytes In those case we allocated @sctx, and sctx->stat.last_physical is all zero (initialized by kvzalloc()). Unfortunately some critical errors happened during scrub_enumerate_chunks() or scrub_supers() before any stripe is really scrubbed. In that case although we will copy sctx->stat back to @progress, since no byte is really scrubbed, last_physical will be overwritten to 0. [FIX] Make sure the parameter @progress always has its @last_physical member updated to @start parameter inside btrfs_scrub_dev(). At the very beginning of the function, set @progress->last_physical to @start, so that even if we error out without doing progress copying, last_physical is still at @start. Then after we got @sctx allocated, set sctx->stat.last_physical to @start, this will make sure even if we didn't get any byte scrubbed, at the progress copying stage the @last_physical is not left as zero. This should resolve the resume progress reset problem. Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.