On Tue, Mar 17, 2020 at 05:54:00AM -0300, Bruno Meneguele wrote: > On Tue, Mar 17, 2020 at 11:03:26AM +0900, Sergey Senozhatsky wrote: > > On (20/03/13 08:02), Bruno Meneguele wrote: > > > Ok, I poorly expressed the notion of "documentantion". The userspace > > > doesn't tell about returning -ESPIPE, but to the functions work properly > > > they watch for -ESPIPE returning from the syscall. For instance, gblic > > > dprintf() implementation: > > > > > > dprintf: > > > __vdprintf_internal: > > > _IO_new_file_attach: > > > > > > if (_IO_SEEKOFF (fp, (off64_t)0, _IO_seek_cur, _IOS_INPUT|_IOS_OUTPUT) > > > == _IO_pos_BAD && errno != ESPIPE) > > > return NULL; > > > > > > With that, if the seek fails, but return anything other than ESPIPE the > > > dprintf() will also fail returning -EINVAL to dprintf() caller. While if > > > ESPIPE is returned, it's "ignored" and the call still works. The way we > > > have today make kmsg an exception case among the rest of the system > > > files where you can open with dprintf. > > > > > > One of the things I could agree with is removing the SEEK call from > > > dprintf, since fprintf basically follows the same steps, but doesn't > > > seek anything. But at the same time, IMO it makes sense to make kmsg > > > interface complaint with the errno return values. > > > > The code in questions is very old. So let's add the missing bit to the > > kernel. At the same time, we probably can have a slightly more detailed > > documentation / code comment. > > > > -ss > > > > Sure thing. > > I'm going to send a v2 of this patch with more details still today or > tomorrow. > > Thanks! > Just fyi, v2 was posted: https://lkml.org/lkml/2020/3/17/321 -- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
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