65adc27375
Add a new rg_skip field to struct gfs2_rgrp, replacing __pad. The rg_skip field has the following meaning: - If rg_skip is zero, it is considered unset and not useful. - If rg_skip is non-zero, its value will be the number of blocks between this rgrp's address and the next rgrp's address. This can be used as a hint by fsck.gfs2 when rebuilding a bad rindex, for example. This will provide less dependency on the rindex in future, and allow tools such as fsck.gfs2 to iterate the resource groups without keeping the rindex around. The field is updated in gfs2_rgrp_out() so that existing file systems will have it set. This means that any resource groups that aren't ever written will not be updated. The final rgrp is a special case as there is no next rgrp, so it will always have a rg_skip of 0 (unless the fs is extended). Before this patch, gfs2_rgrp_out() zeroes the __pad field explicitly, so the rg_skip field can get set back to 0 in cases where nodes with and without this patch are mixed in a cluster. In some cases, the field may bounce between being set by one node and then zeroed by another which may harm performance slightly, e.g. when two nodes create many small files. In testing this situation is rare but it becomes more likely as the filesystem fills up and there are fewer resource groups to choose from. The problem goes away when all nodes are running with this patch. Dipping into the space currently occupied by the rg_reserved field would have resulted in the same problem as it is also explicitly zeroed, so unfortunately there is no other way around it. Signed-off-by: Andrew Price <anprice@redhat.com> Signed-off-by: Bob Peterson <rpeterso@redhat.com> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.