# 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 # 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 # Reviewed-by: Steven Rostedt (VMware) # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-gcc --version # < /opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-ld --version # < git log --format=%s --max-count=1 ee5e001196d1345b8fee25925ff5f1d67936081e # < make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- axs101_defconfig # Added to kconfig CONFIG_INITRAMFS_SOURCE="" # yes \n | make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- oldconfig yes: standard output: Broken pipe # make -s -j 8 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- /kisskb/src/arch/arc/boot/dts/axs10x_mb.dtsi:221.15-225.6: Warning (i2c_bus_reg): /axs10x_mb/i2c@0x1f000/eeprom@0x54: I2C bus unit address format error, expected "54" /kisskb/src/arch/arc/boot/dts/axs10x_mb.dtsi:227.15-231.6: Warning (i2c_bus_reg): /axs10x_mb/i2c@0x1f000/eeprom@0x57: I2C bus unit address format error, expected "57" /kisskb/src/arch/arc/mm/tlb.c: In function 'do_tlb_overlap_fault': /kisskb/src/arch/arc/mm/tlb.c:914:2: warning: variable length array 'pd0' is used [-Wvla] unsigned int pd0[mmu->ways]; ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/include/linux/list.h:9, from /kisskb/src/include/linux/wait.h:7, from /kisskb/src/include/linux/wait_bit.h:8, from /kisskb/src/include/linux/fs.h:6, from /kisskb/src/fs/nfs/nfs3acl.c:2: /kisskb/src/fs/nfs/nfs3acl.c: In function 'nfs3_abort_get_acl': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/fs/nfs/nfs3acl.c:44:2: note: in expansion of macro 'cmpxchg' cmpxchg(p, sentinel, ACL_NOT_CACHED); ^ /kisskb/src/net/ipv4/tcp_input.c: In function 'tcp_data_queue': /kisskb/src/net/ipv4/tcp_input.c:4324:49: warning: array subscript is above array bounds [-Warray-bounds] tp->selective_acks[i-1] = tp->selective_acks[i]; ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/include/linux/list.h:9, from /kisskb/src/include/linux/module.h:9, from /kisskb/src/net/core/filter.c:24: /kisskb/src/net/core/filter.c: In function 'bpf_clear_redirect_map': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/net/core/filter.c:3466:4: note: in expansion of macro 'cmpxchg' cmpxchg(&ri->map, map, NULL); ^ In file included from /kisskb/src/arch/arc/include/asm/atomic.h:16:0, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/arc/include/asm/bitops.h:429, from /kisskb/src/include/linux/bitops.h:19, from /kisskb/src/include/linux/kernel.h:11, from /kisskb/src/fs/posix_acl.c:13: /kisskb/src/fs/posix_acl.c: In function 'get_acl': /kisskb/src/arch/arc/include/asm/cmpxchg.h:95:29: warning: value computed is not used [-Wunused-value] #define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \ ^ /kisskb/src/fs/posix_acl.c:147:3: note: in expansion of macro 'cmpxchg' cmpxchg(p, sentinel, ACL_NOT_CACHED); ^ Completed OK # rm -rf /kisskb/build/linus_axs101_defconfig_arcompact # Build took: 0:01:18.718645