[libvirt] [PATCH option 1] Use fallocate directly if possible

If fallocate() is present, use it directly instead of posix_allocate(). If it is not support by the kernel or filesystem, emulate it using mmap() or write(). This change is to work around slow fallocate emulation done by glibc's posix_allocate() when used on files opened with O_DSYNC. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; --- configure.ac | 2 +- src/util/util.c | 24 +++++++++++++++++++++--- 2 files changed, 22 insertions(+), 4 deletions(-) diff --git a/configure.ac b/configure.ac index 682b8b5..c000ac3 100644 --- a/configure.ac +++ b/configure.ac @@ -104,7 +104,7 @@ dnl Use --disable-largefile if you don't want this. AC_SYS_LARGEFILE dnl Availability of various common functions (non-fatal if missing). -AC_CHECK_FUNCS([cfmakeraw regexec uname sched_getaffinity getuid getgid posix_fallocate mmap]) +AC_CHECK_FUNCS([cfmakeraw regexec uname sched_getaffinity getuid getgid posix_fallocate mmap fallocate]) dnl Availability of various not common threadsafe functions AC_CHECK_FUNCS([strerror_r strtok_r getmntent_r getgrnam_r getpwuid_r]) diff --git a/src/util/util.c b/src/util/util.c index 34c585d..6ecc226 100644 --- a/src/util/util.c +++ b/src/util/util.c @@ -128,7 +128,7 @@ ssize_t safewrite(int fd, const void *buf, size_t count) return nwritten; } -#ifdef HAVE_POSIX_FALLOCATE +#if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE) int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) { return posix_fallocate(fd, offset, len); @@ -136,7 +136,7 @@ int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) #else #ifdef HAVE_MMAP -int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) +static int safezero_mmap(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) { int r; char *buf; @@ -160,7 +160,7 @@ int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) #else /* HAVE_MMAP */ -int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) +static int safezero_write(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) { int r; char *buf; @@ -196,6 +196,24 @@ int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) return 0; } #endif /* HAVE_MMAP */ + +int safezero(int fd, int flags ATTRIBUTE_UNUSED, off_t offset, off_t len) +{ +#ifdef HAVE_FALLOCATE + if (fallocate(fd, 0, offset, len) < 0) { + if (errno != ENOSYS && errno != EOPNOTSUPP) + return -1; + } else + return 0; +#endif + +#ifdef HAVE_MMAP + return safezero_mmap(fd, 0, offset, len); +#else + return safezero_write(fd, 0, offset, len); +#endif +} + #endif /* HAVE_POSIX_FALLOCATE */ #ifndef PROXY -- 1.7.0