On Wed, Oct 09, 2024 at 06:13:39PM +0200, Johannes Berg wrote: > From: Johannes Berg <johannes.berg@xxxxxxxxx> > > As struct file_operations is really big, but (most) debugfs > files only use simple_open, read and write, and don't need > anything else, this wastes a lot of space for NULL pointers. You added llseek too, I'm guessing you need/want that? > Add a struct debugfs_short_fops and some bookkeeping code in > debugfs so that users can use that with debugfs_create_file() > using _Generic to figure out which function to use. That's crazy, but nice work! > Converting mac80211 to use it where possible saves quite a > bit of space: > > 1010127 205064 1220 1216411 128f9b net/mac80211/mac80211.ko (before) > 981199 205064 1220 1187483 121e9b net/mac80211/mac80211.ko (after) > ------- > -28928 = ~28KiB > > With a marginal space cost in debugfs: > > 8701 550 16 9267 2433 fs/debugfs/inode.o (before) > 25233 325 32 25590 63f6 fs/debugfs/file.o (before) > 8914 558 16 9488 2510 fs/debugfs/inode.o (after) > 25380 325 32 25737 6489 fs/debugfs/file.o (after) > --------------- > +360 +8 > > (All on x86-64) > > A simple spatch suggests there are more than 300 instances, > not even counting the ones hidden in macros like in mac80211, > that could be trivially converted, for additional savings of > about 240 bytes for each. > > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> > --- > fs/debugfs/file.c | 100 ++++++++++++++++++++++++++++------------ > fs/debugfs/inode.c | 63 +++++++++++-------------- > fs/debugfs/internal.h | 6 +++ > include/linux/debugfs.h | 60 ++++++++++++++++++++++-- > 4 files changed, 159 insertions(+), 70 deletions(-) That's real savings so I'm all for it unless someone else objects? thanks, greg k-h
