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Matthew Wilcox (Oracle) 7e934cf5ac xarray: Fix early termination of xas_for_each_marked 
xas_for_each_marked() is using entry == NULL as a termination condition
of the iteration. When xas_for_each_marked() is used protected only by
RCU, this can however race with xas_store(xas, NULL) in the following
way:

TASK1                                   TASK2
page_cache_delete()         	        find_get_pages_range_tag()
                                          xas_for_each_marked()
                                            xas_find_marked()
                                              off = xas_find_chunk()

  xas_store(&xas, NULL)
    xas_init_marks(&xas);
    ...
    rcu_assign_pointer(*slot, NULL);
                                              entry = xa_entry(off);

And thus xas_for_each_marked() terminates prematurely possibly leading
to missed entries in the iteration (translating to missing writeback of
some pages or a similar problem).

If we find a NULL entry that has been marked, skip it (unless we're trying
to allocate an entry).

Reported-by: Jan Kara <jack@suse.cz>
CC: stable@vger.kernel.org
Fixes: ef8e5717db ("page cache: Convert delete_batch to XArray")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-03-12 17:42:08 -04:00
..
fault-injection
ktest
kunit kunit/kunit_tool_test: Test '--build_dir' option run 2019-12-23 10:52:41 -07:00
nvdimm tools/testing/nvdimm: Fix mock support for ioremap 2019-12-11 17:11:10 -08:00
radix-tree xarray: Fix early termination of xas_for_each_marked 2020-03-12 17:42:08 -04:00
scatterlist
selftests selftests: mlxsw: qos_mc_aware: Fix mausezahn invocation 2020-01-15 04:16:30 -08:00
vsock