Messages in this thread | | | Date | Fri, 21 Feb 2014 10:45:50 +0100 | From | Jan Kara <> | Subject | Re: [PATCH] ext4: avoid exposure of stale data in ext4_punch_hole() -v2 |
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On Thu 20-02-14 19:21:07, Ted Tso wrote: > On Fri, Sep 27, 2013 at 06:05:17PM +0200, Jan Kara wrote: > > On Fri 27-09-13 19:54:03, Maxim Patlasov wrote: > > > While handling punch-hole fallocate, it's useless to truncate page cache > > > before removing the range from extent tree (or block map in indirect case) > > > because page cache can be re-populated (by read-ahead or read(2) or mmap-ed > > > read) immediately after truncating page cache, but before updating extent > > > tree (or block map). In that case the user will see stale data even after > > > fallocate is completed. > > > > > > Changed in v2 (Thanks to Jan Kara): > > > - Until the problem of data corruption resulting from pages backed by > > > already freed blocks is fully resolved, the simple thing we can do now > > > is to add another truncation of pagecache after punch hole is done. > > The patch looks good. You can add: > > Reviewed-by: Jan Kara <jack@suse.cz> > > I was going through old patches, and it looks like this one got > dropped. My apologies. > > As far as I can tell, the underlying problem in the VFS/MM layer > hasn't been solved yet (Jan, can you confirm?), so I've queued this > patch for the next merge window. Yes, we didn't solve it yet. Thanks for queueing the patch!
Honza
-- Jan Kara <jack@suse.cz> SUSE Labs, CR
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