dcc3eb9638
This patch removes all haphazard code implementing nocow writers exclusion from pending snapshot creation and switches to using the drew lock to ensure this invariant still holds. 'Readers' are snapshot creators from create_snapshot and 'writers' are nocow writers from buffered write path or btrfs_setsize. This locking scheme allows for multiple snapshots to happen while any nocow writers are blocked, since writes to page cache in the nocow path will make snapshots inconsistent. So for performance reasons we'd like to have the ability to run multiple concurrent snapshots and also favors readers in this case. And in case there aren't pending snapshots (which will be the majority of the cases) we rely on the percpu's writers counter to avoid cacheline contention. The main gain from using the drew lock is it's now a lot easier to reason about the guarantees of the locking scheme and whether there is some silent breakage lurking. Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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.