d14e1ca305
This patch adds some instrumentation in gfs2's journal replay that indicates when we're about to overwrite a rgrp for which we already have a valid buffer_head. When this problem occurs, it's a situation in which this node has been granted a rgrp glock and subsequently read in buffer_heads for it, and possibly even made changes to the rgrp bits and/or allocation values. But now another node has failed and forced us to replay its journal, but its journal contains a copy of the same rgrp, without a revoke, which means we're about to overwrite a rgrp that we now rightfully own, with an obsolete copy. That is always a problem. It means the other node (which failed and left its journal to be replayed) failed to flush out its rgrp buffers, write out the revoke, and invalidate its copy before it released the glock to our possession. No node should ever release a glock until its metadata has been written to the journal and revoked and invalidated.. We also kludge around the problem and refuse to replace our good copy with the journals bad copy by not marking the buffer dirty, but never do it silently. That's wallpapering over a larger problem that still exists. IOW, if this situation can happen to this node, it can also happen to a different node and we wouldn't even know it or be able to circumvent it: Suppose we have a 3-node cluster: Node 1 fails, leaving an obsolete rgrp block in its journal without a revoke. Node 2 grabs the rgrp as soon as the rgrp glock is released and starts making changes, allocating and freeing blocks from the rgrp, etc. Node 3 replays the journal from node 1, oblivious and unaware that it's about to overwrite node 2's changes. So we still need to be vocal and log the error to make it apparent that a corruption path still exists in gfs2. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.