Messages in this thread |  | | | Date | Sun, 27 Sep 2009 10:10:35 -0700 | | From | Andrew Morton <> | | Subject | Re: [PATCH] bdi_sync_writeback should WB_SYNC_NONE first |
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On Sun, 27 Sep 2009 18:55:14 +0200 Jens Axboe <jens.axboe@oracle.com> wrote:
> > I wasn't referring to this patch actually. The code as it stands in > > Linus's tree right now attempts to write back up to 2^63 pages... > > I agree, it could make the fs sync take a looong time. This is not a new > issue, though.
It _should_ be a new issue. The old code would estimate the number of dirty pages up-front and would then add a +50% fudge factor, so if we started the sync with 1GB dirty memory, we write back a max of 1.5GB.
However that might have got broken.
void sync_inodes_sb(struct super_block *sb, int wait) { struct writeback_control wbc = { .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE, .range_start = 0, .range_end = LLONG_MAX, }; if (!wait) { unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY); unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS); wbc.nr_to_write = nr_dirty + nr_unstable + (inodes_stat.nr_inodes - inodes_stat.nr_unused); } else wbc.nr_to_write = LONG_MAX; /* doesn't actually matter */ sync_sb_inodes(sb, &wbc); } a) the +50% isn't there in 2.6.31
b) the wait=true case appears to be vulnerable to livelock in 2.6.31.
whodidthat
38f21977663126fef53f5585e7f1653d8ebe55c4 did that back in January.
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