# 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/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-ld --version
# < git log --format=%s --max-count=1 ee5e001196d1345b8fee25925ff5f1d67936081e
# < make -s -j 10 ARCH=arm64 O=/kisskb/build/linus_arm64-allmodconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  allmodconfig
# make -s -j 10 ARCH=arm64 O=/kisskb/build/linus_arm64-allmodconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  
In file included from /kisskb/src/include/asm-generic/bug.h:18,
                 from /kisskb/src/arch/arm64/include/asm/bug.h:37,
                 from /kisskb/src/include/linux/bug.h:5,
                 from /kisskb/src/include/linux/mmdebug.h:5,
                 from /kisskb/src/include/linux/mm.h:9,
                 from /kisskb/src/drivers/dma/imx-dma.c:14:
/kisskb/src/drivers/dma/imx-dma.c: In function 'imxdma_sg_next':
/kisskb/src/include/linux/kernel.h:846:29: warning: comparison of distinct pointer types lacks a cast
   (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
                             ^~
/kisskb/src/include/linux/kernel.h:860:4: note: in expansion of macro '__typecheck'
   (__typecheck(x, y) && __no_side_effects(x, y))
    ^~~~~~~~~~~
/kisskb/src/include/linux/kernel.h:870:24: note: in expansion of macro '__safe_cmp'
  __builtin_choose_expr(__safe_cmp(x, y), \
                        ^~~~~~~~~~
/kisskb/src/include/linux/kernel.h:879:19: note: in expansion of macro '__careful_cmp'
 #define min(x, y) __careful_cmp(x, y, <)
                   ^~~~~~~~~~~~~
/kisskb/src/drivers/dma/imx-dma.c:288:8: note: in expansion of macro 'min'
  now = min(d->len, sg_dma_len(sg));
        ^~~
Completed OK
# rm -rf /kisskb/build/linus_arm64-allmodconfig_arm64-gcc8
# Build took: 0:42:49.991754