Mel Gorman <[email protected]> wrote:
>
> Hi,
>
> I am working on a direct reclaim strategy to free up large blocks of
> contiguous pages. The part I have is working fine, but I am finding a
> hundreds of pages that are being used for inodes that I need to reclaim. I
> tried purging the inode lists using a variation of prune_icache() but it
> is not working out.
>
> Given a struct page, that one knows is an inode, can anyone suggest the
> best way to find the inode using it and free it?
Simple answer: invalidate_mapping_pages(page->mapping, start, end).
Problem: races. If you pick a random page up off the LRU and start playing
with its mapping, what stops that mapping from getting freed under your
feet?
If the caller has a ref on the inode (say, you came in via a syscall
against an fd) then fine.
But if you picked the page up off the LRU then to avoid super-rare oopses
you'll need to pin the address_space somehow. One way is to
a) lock the page, which pins the address_space.
b) check that page->mapping is still non-NULL. Bale if it is.
c) bump page->mapping->host->i_count
d) unlock the page
e) diddle away with the address_space.
f) iput() the inode.
But beware that iput() can do a *ton* of stuff, so you need to be not
holding any locks and to not be called from any fancy contexts.
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