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Dan reports: The patch5e1f0f098b: "mm, compaction: capture a page under direct compaction" from Mar 5, 2019, leads to the following Smatch complaint: mm/compaction.c:2321 compact_zone_order() error: we previously assumed 'capture' could be null (see line 2313) mm/compaction.c 2288 static enum compact_result compact_zone_order(struct zone *zone, int order, 2289 gfp_t gfp_mask, enum compact_priority prio, 2290 unsigned int alloc_flags, int classzone_idx, 2291 struct page **capture) ^^^^^^^ 2313 if (capture) ^^^^^^^ Check for NULL 2314 current->capture_control = &capc; 2315 2316 ret = compact_zone(&cc, &capc); 2317 2318 VM_BUG_ON(!list_empty(&cc.freepages)); 2319 VM_BUG_ON(!list_empty(&cc.migratepages)); 2320 2321 *capture = capc.page; ^^^^^^^^ Unchecked dereference. 2322 current->capture_control = NULL; 2323 In practice this is not an issue, as the only caller path passes non-NULL capture: __alloc_pages_direct_compact() struct page *page = NULL; try_to_compact_pages(capture = &page); compact_zone_order(capture = capture); So let's remove the unnecessary check, which should also make Smatch happy. Fixes:5e1f0f098b("mm, compaction: capture a page under direct compaction") Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Link: http://lkml.kernel.org/r/18b0df3c-0589-d96c-23fa-040798fee187@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.