2009/10/7 Wu Fengguang <fengguang.wu@xxxxxxxxx>:
[...]
> + if (bdi_cap_writeback_dirty(mapping->backing_dev_info) &&
> + !mapping->a_ops->writepages) {
> + wbc.range_start = (page->index + 1) << PAGE_CACHE_SHIFT;
> + wbc.nr_to_write = LUMPY_PAGEOUT_PAGES - 1;
> + generic_writepages(mapping, &wbc);
> + iput(inode);
I am afraid calling iput() from within pageout code is not generally
safe: it can trigger a lot of file system activity (think
open-unlinked file) that is not supposed to happen in the
direct-reclaim context. Limiting pageout clustering to kswapd might be
a better idea---this would improve direct-reclaim latency too, but
still, file systems are not designed for re-entrant calls to iput().
Thank you,
Nikita.
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