Eric Dumazet a écrit :

Jason Gunthorpe a écrit :

quoted

quoted

One way to handle this is to switch tcp_read() to use the underlying file O_NONBLOCK
flag, as other socket operations do. And let SPLICE_F_NONBLOCK control the pipe output only.

arg, this was tcp_splice_read() of course

quoted

Thanks Eric, this seems reasonable from my userspace perspective.

I admit I don't understand why SPLICE_F_NONBLOCK exists, it seems very
un-unixy to have a syscall completely ignore the NONBLOCK flag of the
fd it is called on. Ie setting NONBLOCK on the pipe itself does
nothing when using splice..

Hmm, good question, I dont have the answer but I'll digg one.

commit	29e350944fdc2dfca102500790d8ad6d6ff4f69d
splice: add SPLICE_F_NONBLOCK flag

It doesn't make the splice itself necessarily nonblocking (because the
actual file descriptors that are spliced from/to may block unless they
have the O_NONBLOCK flag set), but it makes the splice pipe operations
nonblocking.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>


See Linus intention was pretty clear : O_NONBLOCK should be taken into account
by 'actual file that are spliced from/to', regardless of SPLICE_F_NONBLOCK flag