• Al Viro's avatar
    fix __swap_writepage() compile failure on old gcc versions · 05064084
    Al Viro authored
    Tetsuo Handa wrote:
     "Commit 62a8067a ("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: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Reported-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    05064084
page_io.c 9.53 KB