# 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/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-ld --version
# < git log --format=%s --max-count=1 ee5e001196d1345b8fee25925ff5f1d67936081e
# < make -s -j 10 ARCH=arm O=/kisskb/build/linus_em_x270_defconfig_arm CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-  em_x270_defconfig
# make -s -j 10 ARCH=arm O=/kisskb/build/linus_em_x270_defconfig_arm CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-  
/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]
/kisskb/src/drivers/base/regmap/regmap.c: In function 'regmap_raw_read':
/kisskb/src/drivers/base/regmap/regmap.c:2594:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write':
/kisskb/src/drivers/base/regmap/regmap.c:1855:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here
/kisskb/src/net/ipv4/ip_output.c: In function '__ip_append_data':
/kisskb/src/include/linux/skbuff.h:1338:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv4/ip_output.c:885:14: note: 'extra_uref' was declared here
/kisskb/src/drivers/i2c/i2c-core-base.c: In function 'i2c_generic_scl_recovery':
/kisskb/src/drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
Completed OK
# rm -rf /kisskb/build/linus_em_x270_defconfig_arm
# Build took: 0:00:51.383170