The last version had a nasty data corruption inducing
off by one issue. I'll apply the attached this evening.
cheers,
Pádraig.
From 40d1676c087cc79a059b9b0a7207f9eb9f66f074 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= p...@draigbrady.com
Date: Tue, 5 Apr 2011 11:04:13 +0100
Subject: [PATCH] copy: handle mergeable extents across fiemap scans
* extent-scan.h (extent_scan_free): Init the pointer to NULL,
and reset the count to 0, so that we can realloc the buffer.
* src/extent-scan.c (extent_scan_init): Likewise.
(extent_scan_read): Loop over multiple fiemap scans, so we handle
mergeable extents that span across fiemap scan boundaries. Once
we have enough unique extents, return so as to minimize memory use.
---
src/extent-scan.c | 194 +
src/extent-scan.h |2 +
2 files changed, 108 insertions(+), 88 deletions(-)
diff --git a/src/extent-scan.c b/src/extent-scan.c
index c0a5de6..e56927b 100644
--- a/src/extent-scan.c
+++ b/src/extent-scan.c
@@ -67,6 +67,7 @@ extent_scan_init (int src_fd, struct extent_scan *scan)
{
scan-fd = src_fd;
scan-ei_count = 0;
+ scan-ext_info = NULL;
scan-scan_start = 0;
scan-initial_scan_failed = false;
scan-hit_final_extent = false;
@@ -82,108 +83,125 @@ extent_scan_init (int src_fd, struct extent_scan *scan)
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 = scan-fm_flags;
- 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, si = 0;
+ unsigned int si = 0;
struct extent_info *last_ei IF_LINT ( = scan-ext_info);
- for (i = 0; i scan-ei_count; i++)
+ while (true)
{
- assert (fm_extents[i].fe_logical = OFF_T_MAX - fm_extents[i].fe_length);
+ 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 1);
+
+ /* 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 = scan-fm_flags;
+ 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 (si last_ei-ext_flags ==
- (fm_extents[i].fe_flags ~FIEMAP_EXTENT_LAST)
- (last_ei-ext_logical + last_ei-ext_length
- == fm_extents[i].fe_logical))
+ /* If 0 extents are returned, then no more scans are needed. */
+ if (fiemap-fm_mapped_extents == 0)
{
- /* Merge previous with last. */
- last_ei-ext_length += fm_extents[i].fe_length;
- /* Copy flags in case different. */
- last_ei-ext_flags = fm_extents[i].fe_flags;
+ scan-hit_final_extent = true;
+ return scan-scan_start != 0;
}
- else if ((si == 0 scan-scan_start fm_extents[i].fe_logical)
- || (si last_ei-ext_logical + last_ei-ext_length
- fm_extents[i].fe_logical))
+
+ assert (scan-ei_count = SIZE_MAX - fiemap-fm_mapped_extents);
+ scan-ei_count += fiemap-fm_mapped_extents;
+ scan-ext_info = xnrealloc (scan-ext_info, scan-ei_count,
+ sizeof (struct extent_info));
+
+ unsigned int i = 0;
+
