[f2fs-dev] [PATCH v2 1/2] f2fs-tools: use pread and pwrite when they are available.

[LongPing Wei via Linux-f2fs-devel]

This patch wants to reduce the number of system calls to improve performance.
pread and pwrite will only be used when the target platform support them.

Signed-off-by: LongPing Wei <weilongp...@oppo.com>
---
 configure.ac     |  4 +++-
 lib/libf2fs_io.c | 32 +++++++++++++++++++++++++++++---
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 2053a65..ddfc3b0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -182,6 +182,7 @@ AC_TYPE_SIZE_T
 AC_FUNC_GETMNTENT
 AC_CHECK_FUNCS_ONCE([
        add_key
+       clock_gettime
        fallocate
        fsetxattr
        fstat
@@ -192,8 +193,9 @@ AC_CHECK_FUNCS_ONCE([
        getuid
        keyctl
        memset
+       pread
+       pwrite
        setmntent
-       clock_gettime
 ])
 
 AS_IF([test "$ac_cv_header_byteswap_h" = "yes"],
diff --git a/lib/libf2fs_io.c b/lib/libf2fs_io.c
index 520ae03..2030440 100644
--- a/lib/libf2fs_io.c
+++ b/lib/libf2fs_io.c
@@ -279,6 +279,12 @@ static int dcache_io_read(long entry, __u64 offset, off_t 
blk)
        if (fd < 0)
                return fd;
 
+#ifdef HAVE_PREAD
+       if (pread(fd, dcache_buf + entry * F2FS_BLKSIZE, F2FS_BLKSIZE, offset) 
< 0) {
+               MSG(0, "\n pread() fail.\n");
+               return -1;
+       }
+#else
        if (lseek(fd, offset, SEEK_SET) < 0) {
                MSG(0, "\n lseek fail.\n");
                return -1;
@@ -287,6 +293,7 @@ static int dcache_io_read(long entry, __u64 offset, off_t 
blk)
                MSG(0, "\n read() fail.\n");
                return -1;
        }
+#endif
        dcache_lastused[entry] = ++dcache_usetick;
        dcache_valid[entry] = true;
        dcache_blk[entry] = blk;
@@ -393,10 +400,15 @@ int dev_read_version(void *buf, __u64 offset, size_t len)
 {
        if (c.sparse_mode)
                return 0;
+#ifdef HAVE_RPEAD
+       if (pread(c.kd, buf, len, (off_t)offset) < 0)
+               return -1;
+#else
        if (lseek(c.kd, (off_t)offset, SEEK_SET) < 0)
                return -1;
        if (read(c.kd, buf, len) < 0)
                return -1;
+#endif
        return 0;
 }
 
@@ -535,10 +547,15 @@ int dev_read(void *buf, __u64 offset, size_t len)
        fd = __get_device_fd(&offset);
        if (fd < 0)
                return fd;
+#ifdef HAVE_PREAD
+       if (pread(fd, buf, len, (off_t)offset) < 0)
+               return -1;
+#else
        if (lseek(fd, (off_t)offset, SEEK_SET) < 0)
                return -1;
        if (read(fd, buf, len) < 0)
                return -1;
+#endif
        return 0;
 }
 
@@ -615,9 +632,6 @@ static int __dev_write(void *buf, __u64 offset, size_t len, 
enum rw_hint whint)
        if (fd < 0)
                return fd;
 
-       if (lseek(fd, (off_t)offset, SEEK_SET) < 0)
-               return -1;
-
 #if ! defined(__MINGW32__)
        if (c.need_whint && (c.whint != whint)) {
                u64 hint = whint;
@@ -629,8 +643,15 @@ static int __dev_write(void *buf, __u64 offset, size_t 
len, enum rw_hint whint)
        }
 #endif
 
+#ifdef HAVE_PWRITE
+       if (pwrite(fd, buf, len, (off_t)offset) < 0)
+               return -1;
+#else
+       if (lseek(fd, (off_t)offset, SEEK_SET) < 0)
+               return -1;
        if (write(fd, buf, len) < 0)
                return -1;
+#endif
 
        c.need_fsync = true;
 
@@ -663,10 +684,15 @@ int dev_write_block(void *buf, __u64 blk_addr, enum 
rw_hint whint)
 
 int dev_write_dump(void *buf, __u64 offset, size_t len)
 {
+#ifdef HAVE_PWRITE
+       if (pwrite(c.dump_fd, buf, len, (off_t)offset) < 0)
+               return -1;
+#else
        if (lseek(c.dump_fd, (off_t)offset, SEEK_SET) < 0)
                return -1;
        if (write(c.dump_fd, buf, len) < 0)
                return -1;
+#endif
        return 0;
 }
 
-- 
2.34.1



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