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Message-ID: <1375088785-30653-3-git-send-email-liezhi.yang@windriver.com>
Date: Mon, 29 Jul 2013 17:06:25 +0800
From: Robert Yang <liezhi.yang@...driver.com>
To: <linux-ext4@...r.kernel.org>
CC: <tytso@....edu>, <dvhart@...ux.intel.com>,
<darrick.wong@...cle.com>
Subject: [PATCH 2/2] 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@...driver.com>
Acked-by: Darren Hart <dvhart@...ux.intel.com>
---
debugfs/debugfs.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 57 insertions(+), 4 deletions(-)
diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index a6bc932..d35fecc 100644
--- 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;
@@ -1575,22 +1585,36 @@ 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");
+ return retval;
+ }
+
while (1) {
- got = read(fd, buf, sizeof(buf));
+ got = read(fd, buf, bufsize);
if (got == 0)
break;
if (got < 0) {
@@ -1598,6 +1622,21 @@ 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);
@@ -1608,10 +1647,14 @@ 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;
}
@@ -1624,6 +1667,8 @@ 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))
@@ -1699,7 +1744,15 @@ 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);
}
--
1.8.1.2
--
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