From 05064084e82d057f8d74590c51581650e060fbb8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 14 Jun 2014 07:12:41 +0100 Subject: [PATCH] fix __swap_writepage() compile failure on old gcc versions Tetsuo Handa wrote: "Commit 62a8067a7f35 ("bio_vec-backed iov_iter") introduced an unnamed union inside a struct which gcc-4.4.7 cannot handle. Name the unnamed union as u in order to fix build failure" Let's do this instead: there is only one place in the entire tree that steps into this breakage. Anon structs and unions work in older gcc versions; as the matter of fact, we have those in the tree - see e.g. struct ieee80211_tx_info in include/net/mac80211.h What doesn't work is handling their initializers: struct { int a; union { int b; char c; }; } x[2] = {{.a = 1, .c = 'a'}, {.a = 0, .b = 1}}; is the obvious syntax for initializer, perfectly fine for C11 and handled correctly by gcc-4.7 or later. Earlier versions, though, break on it - declaration is fine and so's access to fields (i.e. x[0].c = 'a'; would produce the right code), but members of the anon structs and unions are not inserted into the right namespace. Tellingly, those older versions will not barf on struct {int a; struct {int a;};}; - looks like they just have it hacked up somewhere around the handling of . and -> instead of doing the right thing. The easiest way to deal with that crap is to turn initialization of those fields (in the only place where we have such initializer of iov_iter) into plain assignment. Reported-by: Tetsuo Handa Reported-by: Russell King Signed-off-by: Al Viro Signed-off-by: Linus Torvalds --- mm/page_io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_io.c b/mm/page_io.c index 243a9b76e5ce..955db8b0d497 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -274,8 +274,8 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, .count = PAGE_SIZE, .iov_offset = 0, .nr_segs = 1, - .bvec = &bv }; + from.bvec = &bv; /* older gcc versions are broken */ init_sync_kiocb(&kiocb, swap_file); kiocb.ki_pos = page_file_offset(page); -- 2.20.1