Commit 55635ba7 authored May 03, 2017 by Andrey Ryabinin Committed by Linus Torvalds May 03, 2017

fs: fix data invalidation in the cleancache during direct IO

Patch series "Properly invalidate data in the cleancache", v2.

We've noticed that after direct IO write, buffered read sometimes gets
stale data which is coming from the cleancache.  The reason for this is
that some direct write hooks call call invalidate_inode_pages2[_range]()
conditionally iff mapping->nrpages is not zero, so we may not invalidate
data in the cleancache.

Another odd thing is that we check only for ->nrpages and don't check
for ->nrexceptional, but invalidate_inode_pages2[_range] also
invalidates exceptional entries as well.  So we invalidate exceptional
entries only if ->nrpages != 0? This doesn't feel right.

 - Patch 1 fixes direct IO writes by removing ->nrpages check.
 - Patch 2 fixes similar case in invalidate_bdev().
     Note: I only fixed conditional cleancache_invalidate_inode() here.
       Do we also need to add ->nrexceptional check in into invalidate_bdev()?

 - Patches 3-4: some optimizations.

This patch (of 4):

Some direct IO write fs hooks call invalidate_inode_pages2[_range]()
conditionally iff mapping->nrpages is not zero.  This can't be right,
because invalidate_inode_pages2[_range]() also invalidate data in the
cleancache via cleancache_invalidate_inode() call.  So if page cache is
empty but there is some data in the cleancache, buffered read after
direct IO write would get stale data from the cleancache.

Also it doesn't feel right to check only for ->nrpages because
invalidate_inode_pages2[_range] invalidates exceptional entries as well.

Fix this by calling invalidate_inode_pages2[_range]() regardless of
nrpages state.

Note: nfs,cifs,9p doesn't need similar fix because the never call
cleancache_get_page() (nor directly, nor via mpage_readpage[s]()), so
they are not affected by this bug.

Fixes: c515e1fd ("mm/fs: add hooks to support cleancache")
Link: http://lkml.kernel.org/r/20170424164135.22350-2-aryabinin@virtuozzo.com


Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Kuznetsov <kuznet@virtuozzo.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Nikolay Borisov <n.borisov.lkml@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f0fe9984

fs/iomap.c

+8 −10

Original line number	Diff line number	Diff line
		@@ -887,7 +887,6 @@ iomap_dio_rw(struct kiocb iocb, struct iov_iter iter,
		flags \|= IOMAP_WRITE;
		}

		if (mapping->nrpages) {
		ret = filemap_write_and_wait_range(mapping, start, end);
		if (ret)
		goto out_free_dio;
		@@ -896,7 +895,6 @@ iomap_dio_rw(struct kiocb iocb, struct iov_iter iter,
		start >> PAGE_SHIFT, end >> PAGE_SHIFT);
		WARN_ON_ONCE(ret);
		ret = 0;
		}

		inode_dio_begin(inode);

		@@ -951,7 +949,7 @@ iomap_dio_rw(struct kiocb iocb, struct iov_iter iter,
		* one is a pretty crazy thing to do, so we don't support it 100%. If
		* this invalidation fails, tough, the write still worked...
		*/
		if (iov_iter_rw(iter) == WRITE && mapping->nrpages) {
		if (iov_iter_rw(iter) == WRITE) {
		int err = invalidate_inode_pages2_range(mapping,
		start >> PAGE_SHIFT, end >> PAGE_SHIFT);
		WARN_ON_ONCE(err);

mm/filemap.c

+11 −15

Original line number	Diff line number	Diff line
		@@ -2720,7 +2720,6 @@ generic_file_direct_write(struct kiocb iocb, struct iov_iter from)
		* about to write. We do this before the write so that we can return
		* without clobbering -EIOCBQUEUED from ->direct_IO().
		*/
		if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
		pos >> PAGE_SHIFT, end);
		/*
		@@ -2732,7 +2731,6 @@ generic_file_direct_write(struct kiocb iocb, struct iov_iter from)
		return 0;
		goto out;
		}
		}

		written = mapping->a_ops->direct_IO(iocb, from);

		@@ -2744,10 +2742,8 @@ generic_file_direct_write(struct kiocb iocb, struct iov_iter from)
		* so we don't support it 100%. If this invalidation
		* fails, tough, the write still worked...
		*/
		if (mapping->nrpages) {
		invalidate_inode_pages2_range(mapping,
		pos >> PAGE_SHIFT, end);
		}

		if (written > 0) {
		pos += written;

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