# git rev-parse -q --verify ee5e001196d1345b8fee25925ff5f1d67936081e^{commit}
ee5e001196d1345b8fee25925ff5f1d67936081e
already have revision, skipping fetch
# git checkout -q -f -B kisskb ee5e001196d1345b8fee25925ff5f1d67936081e
# git clean -qxdf
# < git log -1
# commit ee5e001196d1345b8fee25925ff5f1d67936081e
# Author: Slavomir Kaslev <kaslevs@vmware.com>
# Date:   Thu Feb 7 17:45:19 2019 +0200
# 
#     fs: Make splice() and tee() take into account O_NONBLOCK flag on pipes
#     
#     The current implementation of splice() and tee() ignores O_NONBLOCK set
#     on pipe file descriptors and checks only the SPLICE_F_NONBLOCK flag for
#     blocking on pipe arguments.  This is inconsistent since splice()-ing
#     from/to non-pipe file descriptors does take O_NONBLOCK into
#     consideration.
#     
#     Fix this by promoting O_NONBLOCK, when set on a pipe, to
#     SPLICE_F_NONBLOCK.
#     
#     Some context for how the current implementation of splice() leads to
#     inconsistent behavior.  In the ongoing work[1] to add VM tracing
#     capability to trace-cmd we stream tracing data over named FIFOs or
#     vsockets from guests back to the host.
#     
#     When we receive SIGINT from user to stop tracing, we set O_NONBLOCK on
#     the input file descriptor and set SPLICE_F_NONBLOCK for the next call to
#     splice().  If splice() was blocked waiting on data from the input FIFO,
#     after SIGINT splice() restarts with the same arguments (no
#     SPLICE_F_NONBLOCK) and blocks again instead of returning -EAGAIN when no
#     data is available.
#     
#     This differs from the splice() behavior when reading from a vsocket or
#     when we're doing a traditional read()/write() loop (trace-cmd's
#     --nosplice argument).
#     
#     With this patch applied we get the same behavior in all situations after
#     setting O_NONBLOCK which also matches the behavior of doing a
#     read()/write() loop instead of splice().
#     
#     This change does have potential of breaking users who don't expect
#     EAGAIN from splice() when SPLICE_F_NONBLOCK is not set.  OTOH programs
#     that set O_NONBLOCK and don't anticipate EAGAIN are arguably buggy[2].
#     
#      [1] https://github.com/skaslev/trace-cmd/tree/vsock
#      [2] https://github.com/torvalds/linux/blob/d47e3da1759230e394096fd742aad423c291ba48/fs/read_write.c#L1425
#     
#     Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com>
#     Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-ld --version
# < git log --format=%s --max-count=1 ee5e001196d1345b8fee25925ff5f1d67936081e
# < make -s -j 10 ARCH=mips O=/kisskb/build/linus_mips-allnoconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  allnoconfig
# make -s -j 10 ARCH=mips O=/kisskb/build/linus_mips-allnoconfig_mips CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/mips-linux/bin/mips-linux-  
/kisskb/src/arch/mips/vdso/Makefile:39: MIPS VDSO requires binutils >= 2.25
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:186:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
FIT description: Linux 5.0.0+
Created:         Tue Mar  5 14:47:13 2019
 Image 0 (kernel@0)
  Description:  Linux 5.0.0+
  Created:      Tue Mar  5 14:47:13 2019
  Type:         Kernel Image
  Compression:  gzip compressed
  Data Size:    625097 Bytes = 610.45 KiB = 0.60 MiB
  Architecture: MIPS
  OS:           Linux
  Load Address: 0x80100000
  Entry Point:  0x80215e80
  Hash algo:    sha1
  Hash value:   2481516fae7c5c7f326bedeadcb92984b9ef1adf
 Default Configuration: 'conf@default'
 Configuration 0 (conf@default)
  Description:  Generic Linux kernel
  Kernel:       kernel@0
Completed OK
# rm -rf /kisskb/build/linus_mips-allnoconfig_mips
# Build took: 0:00:16.731664