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/* extent-scan.c -- core functions for scanning extents
Copyright (C) 2010 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Written by Jie Liu (jeff.liu@oracle.com). */
#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <assert.h>
#include "system.h"
#include "extent-scan.h"
#include "error.h"
#include "quote.h"
#ifndef HAVE_FIEMAP
# include "fiemap.h"
#endif
/* Allocate space for struct extent_scan, initialize the entries if
necessary and return it as the input argument of extent_scan_read(). */
extern void
extent_scan_init (int src_fd, struct extent_scan *scan)
{
scan->fd = src_fd;
scan->ei_count = 0;
scan->scan_start = 0;
scan->initial_scan_failed = false;
scan->hit_final_extent = false;
}
#ifdef __linux__
# ifndef FS_IOC_FIEMAP
# define FS_IOC_FIEMAP _IOWR ('f', 11, struct fiemap)
# endif
/* Call ioctl(2) with FS_IOC_FIEMAP (available in linux 2.6.27) to
obtain a map of file extents excluding holes. */
extern bool
extent_scan_read (struct extent_scan *scan)
{
union { struct fiemap f; char c[4096]; } fiemap_buf;
struct fiemap *fiemap = &fiemap_buf.f;
struct fiemap_extent *fm_extents = &fiemap->fm_extents[0];
enum { count = (sizeof fiemap_buf - sizeof *fiemap) / sizeof *fm_extents };
verify (count != 0);
/* This is required at least to initialize fiemap->fm_start,
but also serves (in mid 2010) to appease valgrind, which
appears not to know the semantics of the FIEMAP ioctl. */
memset (&fiemap_buf, 0, sizeof fiemap_buf);
fiemap->fm_start = scan->scan_start;
fiemap->fm_flags = FIEMAP_FLAG_SYNC;
fiemap->fm_extent_count = count;
fiemap->fm_length = FIEMAP_MAX_OFFSET - scan->scan_start;
/* Fall back to the standard copy if call ioctl(2) failed for the
the first time. */
if (ioctl (scan->fd, FS_IOC_FIEMAP, fiemap) < 0)
{
if (scan->scan_start == 0)
scan->initial_scan_failed = true;
return false;
}
/* If 0 extents are returned, then more get_extent_table() are not needed. */
if (fiemap->fm_mapped_extents == 0)
{
scan->hit_final_extent = true;
return false;
}
scan->ei_count = fiemap->fm_mapped_extents;
scan->ext_info = xnmalloc (scan->ei_count, sizeof (struct extent_info));
unsigned int i;
for (i = 0; i < scan->ei_count; i++)
{
assert (fm_extents[i].fe_logical <= OFF_T_MAX);
scan->ext_info[i].ext_logical = fm_extents[i].fe_logical;
scan->ext_info[i].ext_length = fm_extents[i].fe_length;
scan->ext_info[i].ext_flags = fm_extents[i].fe_flags;
}
i--;
if (scan->ext_info[i].ext_flags & FIEMAP_EXTENT_LAST)
{
scan->hit_final_extent = true;
return true;
}
scan->scan_start = fm_extents[i].fe_logical + fm_extents[i].fe_length;
return true;
}
#else
extern bool extent_scan_read (ignored) { errno = ENOTSUP; return false; }
#endif
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