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During defrag, at btrfs_defrag_file(), we have this loop that iterates over a file range in steps no larger than 256K subranges. If the range is too long, there's no way to interrupt it. So make the loop check in each iteration if there's signal pending, and if there is, break and return -AGAIN to userspace. Before kernel 5.16, we used to allow defrag to be cancelled through a signal, but that was lost with commit7b508037d4("btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()"). This change adds back the possibility to cancel a defrag with a signal and keeps the same semantics, returning -EAGAIN to user space (and not the usually more expected -EINTR). This is also motivated by a recent bug on 5.16 where defragging a 1 byte file resulted in iterating from file range 0 to (u64)-1, as hitting the bug triggered a too long loop, basically requiring one to reboot the machine, as it was not possible to cancel defrag. Fixes:7b508037d4("btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()") CC: stable@vger.kernel.org # 5.16 Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Filipe Manana <fdmanana@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 Restructured Text 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.