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313facc5bd
Snapshot-aware defrag has been disabled since commit8101c8dbf6("Btrfs: disable snapshot aware defrag for now") almost 6 years ago. Let's remove the dead code. If someone is up to the task of bringing it back, they can dig it up from git. This is logically a revert of commit38c227d87c("Btrfs: snapshot-aware defrag") except that now we have to clear the EXTENT_DEFRAG bit to avoid need_force_cow() returning true forever. The reasons to disable were caused by runtime problems (like long stalls or memory consumption) on heavily referenced extents (eg. thousands of snapshots). There were attempts to fix that but never finished. Current defrag breaks the extent references and some users prefer that behaviour over the one implemented by snapshot aware (ie. keeping links for defragmentation). To enable both usecases we'd need to extend defrag ioctl but let's do that properly from scratch. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Omar Sandoval <osandov@fb.com> Reviewed-by: David Sterba <dsterba@suse.com> [ enhance ] 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.