e2image.c (output_meta_data_blocks): Optimize away excess

	lseek() calls when creating a sparse file.  Fewer system
	calls are a good thing.  <g>

diff --git a/misc/ChangeLog b/misc/ChangeLog
index b82a707..ef8b6e0 100644 (file)
--- a/misc/ChangeLog
+++ b/misc/ChangeLog
@@ -1,3 +1,9 @@
+2001-10-12  Theodore Tso  <tytso@valinux.com>
+
+       * e2image.c (output_meta_data_blocks): Optimize away excess
+               lseek() calls when creating a sparse file.  Fewer system
+               calls are a good thing.  <g>
+
 2001-10-07  Andreas Dilger  <adilger@turbolinux.com>
 
        * mke2fs.c (main): Always exit with non-zero code in case of error.

diff --git a/misc/e2image.c b/misc/e2image.c
index fe2f2b2..ccabb19 100644 (file)
--- a/misc/e2image.c
+++ b/misc/e2image.c
@@ -265,18 +265,31 @@ static int check_zero_block(char *buf, int blocksize)
        return 1;
 }
 
-static void write_block(int fd, char *buf, int blocksize, blk_t block)
+static void write_block(int fd, char *buf, int sparse_offset,
+                       int blocksize, blk_t block)
 {
        int             count;
        errcode_t       err;
 
-       count = write(fd, buf, blocksize);
-       if (count != blocksize) {
-               if (count == -1)
-                       err = errno;
-               else
-                       err = 0;
-               com_err(program_name, err, "error writing block %d", block);
+       if (sparse_offset) {
+#ifdef HAVE_LSEEK64
+               if (lseek64(fd, sparse_offset, SEEK_CUR) < 0)
+                       perror("lseek");
+#else
+               if (lseek(fd, sparse_offset, SEEK_CUR) < 0)
+                       perror("lseek");
+#endif
+       }
+       if (blocksize) {
+               count = write(fd, buf, blocksize);
+               if (count != blocksize) {
+                       if (count == -1)
+                               err = errno;
+                       else
+                               err = 0;
+                       com_err(program_name, err, "error writing block %d", 
+                               block);
+               }
        }
 }
 
@@ -285,6 +298,7 @@ static output_meta_data_blocks(ext2_filsys fs, int fd)
        errcode_t       retval;
        blk_t           blk;
        char            buf[8192], zero_buf[8192];
+       int             sparse = 0;
 
        memset(zero_buf, 0, sizeof(zero_buf));
        for (blk = 0; blk < fs->super->s_blocks_count; blk++) {
@@ -297,24 +311,23 @@ static output_meta_data_blocks(ext2_filsys fs, int fd)
                        }
                        if ((fd != 1) && check_zero_block(buf, fs->blocksize))
                                goto sparse_write;
-                       write_block(fd, buf, fs->blocksize, blk);
+                       write_block(fd, buf, sparse, fs->blocksize, blk);
+                       sparse = 0;
                } else {
                sparse_write:
                        if (fd == 1) {
-                               write_block(fd, zero_buf, fs->blocksize, blk);
+                               write_block(fd, zero_buf, 0,
+                                           fs->blocksize, blk);
                                continue;
                        }
-#ifdef HAVE_LSEEK64
-                       if (lseek64(fd, fs->blocksize, SEEK_CUR) < 0)
-                               perror("lseek");
-#else
-                       if (lseek(fd, fs->blocksize, SEEK_CUR) < 0)
-                               perror("lseek");
-#endif                 
+                       sparse += fs->blocksize;
+                       if (sparse >= 1024*1024) {
+                               write_block(fd, 0, sparse, 0, 0);
+                               sparse = 0;
+                       }
                }
        }
-       buf[0] = 0;
-       write(fd, buf, 1);
+       write_block(fd, zero_buf, sparse, 1, -1);
 }
 
 static void write_raw_image_file(ext2_filsys fs, int fd)