Re: [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed,  9 Jun 2010 10:37:18 +1000
Dave Chinner <david@xxxxxxxxxxxxx> wrote:

> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> If a filesystem writes more than one page in ->writepage, write_cache_pages
> fails to notice this and continues to attempt writeback when wbc->nr_to_write
> has gone negative - this trace was captured from XFS:
> 
> 
>     wbc_writeback_start: towrt=1024
>     wbc_writepage: towrt=1024
>     wbc_writepage: towrt=0
>     wbc_writepage: towrt=-1
>     wbc_writepage: towrt=-5
>     wbc_writepage: towrt=-21
>     wbc_writepage: towrt=-85
> 
> This has adverse effects on filesystem writeback behaviour. write_cache_pages()
> needs to terminate after a certain number of pages are written, not after a
> certain number of calls to ->writepage are made.  This is a regression
> introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add
> no_nrwrite_index_update writeback control flag"), but cannot be reverted
> directly due to subsequent bug fixes that have gone in on top of it.

Might be needed in -stable.  Unfortunately the most important piece of
information which is needed to make that decision was cunningly hidden
from us behind the vague-to-the-point-of-uselessness term "adverse
effects".

_what_ "adverse effects"??

--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux