From baa3544609da3c9bbe7e253b83f32df74e1015de Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Sat, 2 Aug 2014 19:18:03 -0400 Subject: [PATCH] libext2fs: have UNIX IO manager use pread/pwrite If pread/pwrite are present, have the UNIX IO manager use them for aligned IOs (instead of the current seek -> read/write), thereby saving us a (minor) amount of system call overhead. Signed-off-by: Darrick J. Wong Signed-off-by: Theodore Ts'o --- configure | 2 +- configure.in | 2 ++ lib/config.h.in | 6 ++++++ lib/ext2fs/unix_io.c | 24 ++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-) diff --git a/configure b/configure index 1886f8f..f0af1d5 100755 --- a/configure +++ b/configure @@ -12994,7 +12994,7 @@ if test "$ac_res" != no; then : fi fi -for ac_func in __secure_getenv backtrace blkid_probe_get_topology blkid_probe_enable_partitions chflags fadvise64 fallocate fallocate64 fchown fdatasync fstat64 ftruncate64 futimes getcwd getdtablesize getmntinfo getpwuid_r getrlimit getrusage jrand48 llseek lseek64 mallinfo mbstowcs memalign mempcpy mmap msync nanosleep open64 pathconf posix_fadvise posix_fadvise64 posix_memalign prctl secure_getenv setmntent setresgid setresuid snprintf srandom stpcpy strcasecmp strdup strnlen strptime strtoull sync_file_range sysconf usleep utime valloc +for ac_func in __secure_getenv backtrace blkid_probe_get_topology blkid_probe_enable_partitions chflags fadvise64 fallocate fallocate64 fchown fdatasync fstat64 ftruncate64 futimes getcwd getdtablesize getmntinfo getpwuid_r getrlimit getrusage jrand48 llseek lseek64 mallinfo mbstowcs memalign mempcpy mmap msync nanosleep open64 pathconf posix_fadvise posix_fadvise64 posix_memalign prctl pread pwrite secure_getenv setmntent setresgid setresuid snprintf srandom stpcpy strcasecmp strdup strnlen strptime strtoull sync_file_range sysconf usleep utime valloc do : as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh` ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var" diff --git a/configure.in b/configure.in index ed9f691..b825f3d 100644 --- a/configure.in +++ b/configure.in @@ -1059,6 +1059,8 @@ AC_CHECK_FUNCS(m4_flatten([ posix_fadvise64 posix_memalign prctl + pread + pwrite secure_getenv setmntent setresgid diff --git a/lib/config.h.in b/lib/config.h.in index be415d8..34fb0cc 100644 --- a/lib/config.h.in +++ b/lib/config.h.in @@ -325,6 +325,9 @@ /* Define to 1 if you have the `prctl' function. */ #undef HAVE_PRCTL +/* Define to 1 if you have the `pread' function. */ +#undef HAVE_PREAD + /* Define if the defines PTHREAD_MUTEX_RECURSIVE. */ #undef HAVE_PTHREAD_MUTEX_RECURSIVE @@ -334,6 +337,9 @@ /* Define to 1 if you have the `putenv' function. */ #undef HAVE_PUTENV +/* Define to 1 if you have the `pwrite' function. */ +#undef HAVE_PWRITE + /* Define to 1 if dirent has d_reclen */ #undef HAVE_RECLEN_DIRENT diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c index e93684e..0dd1490 100644 --- a/lib/ext2fs/unix_io.c +++ b/lib/ext2fs/unix_io.c @@ -130,6 +130,18 @@ static errcode_t raw_read_blk(io_channel channel, size = (count < 0) ? -count : count * channel->block_size; data->io_stats.bytes_read += size; location = ((ext2_loff_t) block * channel->block_size) + data->offset; + +#ifdef HAVE_PREAD + /* Try an aligned pread */ + if ((channel->align == 0) || + (IS_ALIGNED(buf, channel->align) && + IS_ALIGNED(size, channel->align))) { + actual = pread(data->dev, buf, size, location); + if (actual == size) + return 0; + } +#endif /* HAVE_PREAD */ + if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) { retval = errno ? errno : EXT2_ET_LLSEEK_FAILED; goto error_out; @@ -200,6 +212,18 @@ static errcode_t raw_write_blk(io_channel channel, data->io_stats.bytes_written += size; location = ((ext2_loff_t) block * channel->block_size) + data->offset; + +#ifdef HAVE_PWRITE + /* Try an aligned pwrite */ + if ((channel->align == 0) || + (IS_ALIGNED(buf, channel->align) && + IS_ALIGNED(size, channel->align))) { + actual = pwrite(data->dev, buf, size, location); + if (actual == size) + return 0; + } +#endif /* HAVE_PWRITE */ + if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) { retval = errno ? errno : EXT2_ET_LLSEEK_FAILED; goto error_out; -- 1.8.3.1