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Date: Mon, 29 Jul 2013 15:11:45 +0800
From: Robert Yang <liezhi.yang@...driver.com>
To: "Darrick J. Wong" <darrick.wong@...cle.com>
CC: <linux-ext4@...r.kernel.org>, <tytso@....edu>,
<dvhart@...ux.intel.com>
Subject: Re: [PATCH 2/2] debugfs.c: do sparse copy when src is a sparse file
On 07/27/2013 12:02 AM, Darrick J. Wong wrote:
> On Fri, Jul 26, 2013 at 06:30:57PM +0800, Robert Yang wrote:
>> 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 | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 53 insertions(+), 5 deletions(-)
>>
>> diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
>> index b77d0b5..0379f38 100644
>> --- a/debugfs/debugfs.c
>> +++ b/debugfs/debugfs.c
>> @@ -37,6 +37,16 @@ extern char *optarg;
>> #include "../version.h"
>> #include "jfs_user.h"
>>
>> +/* 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;
>> @@ -1571,22 +1581,28 @@ 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 *zeromem;
>> + int cmp;
>>
>> retval = ext2fs_file_open(current_fs, newfile,
>> EXT2_FILE_WRITE, &e2_file);
>> if (retval)
>> return retval;
>>
>> + if (!(buf = (char *) malloc(bufsize))){
>> + fprintf(stderr, "copy_file: can't allocate buffer\n");
>> + return;
>> + }
>> while (1) {
>> - got = read(fd, buf, sizeof(buf));
>> + got = read(fd, buf, bufsize);
>> if (got == 0)
>> break;
>> if (got < 0) {
>> @@ -1594,20 +1610,42 @@ static errcode_t copy_file(int fd, ext2_ino_t newfile)
>> goto fail;
>> }
>> ptr = buf;
>> +
>> + /* Sparse copy */
>> + if (make_holes) {
>> + if (!(zeromem = (char *) calloc(got, 1))) {
>
> Maybe ext2fs_get_memzero()? And I suspect you can allocate a bufsize-sized
> zeromem outside the while loop. Chances are pretty good that if make_holes,
> then buf_size won't be greater than 4096 anyway.
Thanks, sounds great, my testing shows that it is faster for copying the
large sparse file after move the ext2fs_get_memzero() out of the while loop,
and didn't have any obvious impaction for non-sparse file, I will update it
and send a V3.
// Robert
>
> --D
>
>> + fprintf(stderr, "copy_file: can't allocate buffer\n");
>> + return;
>> + }
>> + /* Check whether all is zero */
>> + cmp = memcmp(ptr, zeromem, got);
>> + /* Free it as early as possible */
>> + free(zeromem);
>> + 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);
>> if (retval)
>> goto fail;
>> -
>> got -= written;
>> ptr += written;
>> }
>> }
>> + free(buf);
>> retval = ext2fs_file_close(e2_file);
>> return retval;
>>
>> fail:
>> + free(buf);
>> (void) ext2fs_file_close(e2_file);
>> return retval;
>> }
>> @@ -1620,6 +1658,8 @@ 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))
>> @@ -1684,7 +1724,15 @@ 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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>
>
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