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net: support kmap_local forced debugging in skb_frag_foreach 

Skb frags may be backed by highmem and/or compound pages. Highmem
pages need kmap_atomic mappings to access. But kmap_atomic maps a
single page, not the entire compound page.

skb_foreach_page iterates over an skb frag, in one step in the common
case, page by page only if kmap_atomic must be called for each page.
The decision logic is captured in skb_frag_must_loop.

CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP extends kmap from highmem to all
pages, to increase code coverage.

Extend skb_frag_must_loop to this new condition.

Link: https://lore.kernel.org/linux-mm/20210106180132.41dc249d@gandalf.local.home/
Fixes: 0e91a0c698 ("mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP")
Reported-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
master
Willem de Bruijn 2021-01-09 17:18:32 -05:00 committed by Jakub Kicinski
parent e56b3d94d9
commit 29766bcffa
1 changed files with 1 additions and 1 deletions
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2
include/linux/skbuff.h
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@ -366,7 +366,7 @@ static inline void skb_frag_size_sub(skb_frag_t *frag, int delta)
static inline bool skb_frag_must_loop(struct page *p)
{
#if defined(CONFIG_HIGHMEM)
if (PageHighMem(p))
if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(p))
return true;
#endif
return false;