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libext2fs: have UNIX IO manager use pread/pwrite

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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 <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Darrick J. Wong 2014-08-02 19:18:03 -04:00 committed by Theodore Ts'o
parent af7dbe3a11
commit baa3544609
4 changed files with 33 additions and 1 deletions
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2
configure vendored
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@ -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"

2
configure.in
View File

@ -1059,6 +1059,8 @@ AC_CHECK_FUNCS(m4_flatten([
posix_fadvise64
posix_memalign
prctl
pread
pwrite
secure_getenv
setmntent
setresgid

6
lib/config.h.in
View File

@ -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 <pthread.h> 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

24
lib/ext2fs/unix_io.c
View File

@ -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;