debugfs.c: do sparse copy when src is a sparse file

Let debugfs do sparse copy when src is a sparse file, just like
"cp --sparse=auto"

* For the:
  #define IO_BUFSIZE 64*1024
  this is a suggested value from gnu coreutils:
  http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob;f=src/ioblksize.h;h=1ae93255e7d0ccf0855208c7ae5888209997bf16;hb=HEAD

* Use malloc() to allocate memory for the buffer since put 64K (or
  more) on the stack seems not a good idea.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index 4f19025..5590295 100644 (file)
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -41,6 +41,16 @@ extern char *optarg;
 #define BUFSIZ 8192
 #endif
 
+/* 64KiB is the minimium blksize to best minimize system call overhead. */
+#ifndef IO_BUFSIZE
+#define IO_BUFSIZE 64*1024
+#endif
+
+/* Block size for `st_blocks' */
+#ifndef S_BLKSIZE
+#define S_BLKSIZE 512
+#endif
+
 ss_request_table *extra_cmds;
 const char *debug_prog_name;
 int sci_idx;
@@ -1563,22 +1573,37 @@ void do_find_free_inode(int argc, char *argv[])
 }
 
 #ifndef READ_ONLY
-static errcode_t copy_file(int fd, ext2_ino_t newfile)
+static errcode_t copy_file(int fd, ext2_ino_t newfile, int bufsize, int make_holes)
 {
        ext2_file_t     e2_file;
        errcode_t       retval;
        int             got;
        unsigned int    written;
-       char            buf[8192];
+       char            *buf;
        char            *ptr;
+       char            *zero_buf;
+       int             cmp;
 
        retval = ext2fs_file_open(current_fs, newfile,
                                  EXT2_FILE_WRITE, &e2_file);
        if (retval)
                return retval;
 
+       if (!(buf = (char *) malloc(bufsize))){
+               com_err("copy_file", errno, "can't allocate buffer\n");
+               return;
+       }
+
+       /* This is used for checking whether the whole block is zero */
+       retval = ext2fs_get_memzero(bufsize, &zero_buf);
+       if (retval) {
+               com_err("copy_file", retval, "can't allocate buffer\n");
+               free(buf);
+               return retval;
+       }
+
        while (1) {
-               got = read(fd, buf, sizeof(buf));
+               got = read(fd, buf, bufsize);
                if (got == 0)
                        break;
                if (got < 0) {
@@ -1586,6 +1611,21 @@ static errcode_t copy_file(int fd, ext2_ino_t newfile)
                        goto fail;
                }
                ptr = buf;
+
+               /* Sparse copy */
+               if (make_holes) {
+                       /* Check whether all is zero */
+                       cmp = memcmp(ptr, zero_buf, got);
+                       if (cmp == 0) {
+                                /* The whole block is zero, make a hole */
+                               retval = ext2fs_file_lseek(e2_file, got, EXT2_SEEK_CUR, NULL);
+                               if (retval)
+                                       goto fail;
+                               got = 0;
+                       }
+               }
+
+               /* Normal copy */
                while (got > 0) {
                        retval = ext2fs_file_write(e2_file, ptr,
                                                   got, &written);
@@ -1596,10 +1636,14 @@ static errcode_t copy_file(int fd, ext2_ino_t newfile)
                        ptr += written;
                }
        }
+       free(buf);
+       ext2fs_free_mem(&zero_buf);
        retval = ext2fs_file_close(e2_file);
        return retval;
 
 fail:
+       free(buf);
+       ext2fs_free_mem(&zero_buf);
        (void) ext2fs_file_close(e2_file);
        return retval;
 }
@@ -1612,6 +1656,8 @@ void do_write(int argc, char *argv[])
        ext2_ino_t      newfile;
        errcode_t       retval;
        struct ext2_inode inode;
+       int             bufsize = IO_BUFSIZE;
+       int             make_holes = 0;
 
        if (common_args_process(argc, argv, 3, 3, "write",
                                "<native file> <new file>", CHECK_FS_RW))
@@ -1687,7 +1733,15 @@ void do_write(int argc, char *argv[])
                return;
        }
        if (LINUX_S_ISREG(inode.i_mode)) {
-               retval = copy_file(fd, newfile);
+               if (statbuf.st_blocks < statbuf.st_size / S_BLKSIZE) {
+                       make_holes = 1;
+                       /*
+                        * Use I/O blocksize as buffer size when
+                        * copying sparse files.
+                        */
+                       bufsize = statbuf.st_blksize;
+               }
+               retval = copy_file(fd, newfile, bufsize, make_holes);
                if (retval)
                        com_err("copy_file", retval, 0);
        }