Messages in this thread | | | Subject | Re: [PATCH] mm: cleancache: fix corruption on missed inode invalidation | From | Andrey Ryabinin <> | Date | Mon, 12 Nov 2018 14:40:06 +0300 |
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On 11/12/18 2:31 PM, Jan Kara wrote: > On Mon 12-11-18 12:57:34, Pavel Tikhomirov wrote: >> If all pages are deleted from the mapping by memory reclaim and also >> moved to the cleancache: >> >> __delete_from_page_cache >> (no shadow case) >> unaccount_page_cache_page >> cleancache_put_page >> page_cache_delete >> mapping->nrpages -= nr >> (nrpages becomes 0) >> >> We don't clean the cleancache for an inode after final file truncation >> (removal). >> >> truncate_inode_pages_final >> check (nrpages || nrexceptional) is false >> no truncate_inode_pages >> no cleancache_invalidate_inode(mapping) >> >> These way when reading the new file created with same inode we may get >> these trash leftover pages from cleancache and see wrong data instead of >> the contents of the new file. >> >> Fix it by always doing truncate_inode_pages which is already ready for >> nrpages == 0 && nrexceptional == 0 case and just invalidates inode. >> >> Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache") >> To: Andrew Morton <akpm@linux-foundation.org> >> Cc: Johannes Weiner <hannes@cmpxchg.org> >> Cc: Mel Gorman <mgorman@techsingularity.net> >> Cc: Jan Kara <jack@suse.cz> >> Cc: Matthew Wilcox <willy@infradead.org> >> Cc: Andi Kleen <ak@linux.intel.com> >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Reviewed-by: Vasily Averin <vvs@virtuozzo.com> >> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com> >> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> >> --- >> mm/truncate.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) > > The patch looks good but can you add a short comment before the > truncate_inode_pages() call explaining why it needs to be called always? > Something like: > > /* > * Cleancache needs notification even if there are no pages or > * shadow entries... > */
Or we can just call cleancache_invalidate_inode(mapping) on else branch, so the code would be more self-explanatory, and also avoid function call in no-cleancache setups, which should the most of setups.
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