Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] fscache: fix race between enablement and dropping of object | Date | Wed, 28 Nov 2018 15:12:30 +0000 |
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NeilBrown <neilb@suse.com> wrote:
> It was observed that a process blocked indefintely in > __fscache_read_or_alloc_page(), waiting for FSCACHE_COOKIE_LOOKING_UP > to be cleared via fscache_wait_for_deferred_lookup().
Was there a backtrace for that?
> This leaves a window where something else can set FSCACHE_COOKIE_LOOKING_UP
Attempting to enable the cookie again would have that effect.
> There is some uncertainty in this analysis, but it seems to be fit the > observations. Adding the wake in this patch will be handled correctly > by __fscache_read_or_alloc_page(), as it checks if ->backing_objects > is empty again, after waiting.
That should work. The read op should just then fail with -ENOBUFS, causing the netfs to issue the read over the network instead.
I think there's a more elegant solution to be had, but it'll take some thought as to how to achieve it.
David
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