USER_DS vs oldfs

From: Matthew Wilcox
Date: Wed Sep 29 2004 - 07:23:34 EST



A common idiom in the compat code is:

old_fs = get_fs();
set_fs(KERNEL_DS);
ret = sys_fcntl(fd, (cmd == F_GETLK64) ? F_GETLK :
((cmd == F_SETLK64) ? F_SETLK : F_SETLKW),
(unsigned long)&f);
set_fs(old_fs);

Surely we know that the current 'fs' is USER_DS and so we could simply do:

set_fs(KERNEL_DS);
ret = sys_fcntl(fd, (cmd == F_GETLK64) ? F_GETLK :
((cmd == F_SETLK64) ? F_SETLK : F_SETLKW),
(unsigned long)&f);
set_fs(USER_DS);

--
"Next the statesmen will invent cheap lies, putting the blame upon
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince
himself that the war is just, and will thank God for the better sleep
he enjoys after this process of grotesque self-deception." -- Mark Twain
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