Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) | Date | Tue, 16 Sep 2014 09:44:57 -0400 |
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Milosz Tanski <milosz@adfin.com> writes:
> Jeff, > > This patchset creates a new read (readv2/preadv2) syscall(s) that take > a extra flag argument (kind of like recvmsg). What it doesn't do is > change the current behavior of of the O_NONBLOCK, if the file is > open() with O_NONBLOCK flag. It shouldn't break any existing > applications since you have to opt into using this by using the new > syscall.
Hi, Milosz,
Ah, I misread one of the patches. Now that I've applied the series, I see that you're testing the flag argument, not the file open flags.
> I don't have a preference either way if we should create a new flag or > re-use O_NONBLOCK the flag. Instead, I'm hoping to get some consensus > here from senior kernel developers like yourself. Maybe a RWF_NONBLOCK > (I'm stealing from eventfd, EFD_NONBLOCK).
I think I'd rather name the flag something other than O_NONBLOCK, if for no other reason that to avoid confusion.
> As a side note, I noticed that EFD_NONBLOCK, SFD_NONBLOCK, etc... all > alias to the value of O_NONBLOCK and there's a bunch of bug checks in > the code like this: > BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
That's because the flag is passed on to anon_inode_getfile. See also this define:
#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
A general note on your subjects -- you should make them more specific to the subsystem you're updating. Commit titles like "documentation update" are a bit too broad. ;-)
Cheers, Jeff
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