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[PATCH 04/22] read-cache: Re-read index if index file changed

From
Thomas Gummerer <t.gummerer@gmail.com>
Date
Jul 7, 2013, 08:11 UTC
Message-ID
<1373184720-29767-5-git-send-email-t.gummerer@gmail.com>
In-Reply-To
<1373184720-29767-1-git-send-email-t.gummerer@gmail.com>

Add the possibility of re-reading the index file, if it changed while reading.

The index file might change during the read, causing outdated information to be displayed. We check if the index file changed by using its stat data as heuristic.

Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
---
 read-cache.c | 91 +++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 57 insertions(+), 34 deletions(-)
diff --git a/read-cache.c b/read-cache.c
index 1e7ffc2..3e3a0e2 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1275,11 +1275,31 @@ int read_index(struct index_state *istate)
 	return read_index_from(istate, get_index_file());
 }
 
+static int index_changed(struct stat *st_old, struct stat *st_new)
+{
+	if (st_old->st_mtime != st_new->st_mtime ||
+#if !defined (__CYGWIN__)
+	    st_old->st_uid   != st_new->st_uid ||
+	    st_old->st_gid   != st_new->st_gid ||
+	    st_old->st_ino   != st_new->st_ino ||
+#endif
+#if USE_NSEC
+	    ST_MTIME_NSEC(*st_old) != ST_MTIME_NSEC(*st_new) ||
+#endif
+#if USE_STDEV
+	    st_old->st_dev != st_new->st_dev ||
+#endif
+	    st_old->st_size != st_new->st_size)
+		return 1;
+
+	return 0;
+}
+
 /* remember to discard_cache() before reading a different cache! */
 int read_index_from(struct index_state *istate, const char *path)
 {
-	int fd;
-	struct stat st;
+	int fd, err, i;
+	struct stat st_old, st_new;
 	struct cache_version_header *hdr;
 	void *mmap;
 	size_t mmap_size;
@@ -1291,41 +1311,44 @@ int read_index_from(struct index_state *istate, const char *path)
 	errno = ENOENT;
 	istate->timestamp.sec = 0;
 	istate->timestamp.nsec = 0;
+	for (i = 0; i < 50; i++) {
+		err = 0;
+		fd = open(path, O_RDONLY);
+		if (fd < 0) {
+			if (errno == ENOENT)
+				return 0;
+			die_errno("index file open failed");
+		}
 
-	fd = open(path, O_RDONLY);
-	if (fd < 0) {
-		if (errno == ENOENT)
-			return 0;
-		die_errno("index file open failed");
+		if (fstat(fd, &st_old))
+			die_errno("cannot stat the open index");
+
+		errno = EINVAL;
+		mmap_size = xsize_t(st_old.st_size);
+		mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+		close(fd);
+		if (mmap == MAP_FAILED)
+			die_errno("unable to map index file");
+
+		hdr = mmap;
+		if (verify_hdr_version(istate, hdr, mmap_size) < 0)
+			err = 1;
+
+		if (istate->ops->verify_hdr(mmap, mmap_size) < 0)
+			err = 1;
+
+		if (istate->ops->read_index(istate, mmap, mmap_size) < 0)
+			err = 1;
+		istate->timestamp.sec = st_old.st_mtime;
+		istate->timestamp.nsec = ST_MTIME_NSEC(st_old);
+		if (lstat(path, &st_new))
+			die_errno("cannot stat the open index");
+
+		munmap(mmap, mmap_size);
+		if (!index_changed(&st_old, &st_new) && !err)
+			return istate->cache_nr;
 	}
 
-	if (fstat(fd, &st))
-		die_errno("cannot stat the open index");
-
-	errno = EINVAL;
-	mmap_size = xsize_t(st.st_size);
-	mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-	close(fd);
-	if (mmap == MAP_FAILED)
-		die_errno("unable to map index file");
-
-	hdr = mmap;
-	if (verify_hdr_version(istate, hdr, mmap_size) < 0)
-		goto unmap;
-
-	if (istate->ops->verify_hdr(mmap, mmap_size) < 0)
-		goto unmap;
-
-	if (istate->ops->read_index(istate, mmap, mmap_size) < 0)
-		goto unmap;
-	istate->timestamp.sec = st.st_mtime;
-	istate->timestamp.nsec = ST_MTIME_NSEC(st);
-
-	munmap(mmap, mmap_size);
-	return istate->cache_nr;
-
-unmap:
-	munmap(mmap, mmap_size);
 	die("index file corrupt");
 }
 

-- 
1.8.3.453.g1dfc63d
Previous: Thomas GummererNext: Thomas Gummerer
Message 5 of 51 in “Index v5”
  1. 00/22 Index v5Thomas Gummerer, Jul 7, 2013
  2. 01/22 t2104: Don't fail for index versions other than [23]Thomas Gummerer, Jul 7, 2013
  3. 02/22 read-cache: split index file version specific functionalityThomas Gummerer, Jul 7, 2013
  4. 03/22 read-cache: move index v2 specific functions to their own fileThomas Gummerer, Jul 7, 2013
  5. 04/22 read-cache: Re-read index if index file changedThomas Gummerer, Jul 7, 2013
  6. 05/22 read-cache: add index reading apiThomas Gummerer, Jul 7, 2013
  7. Duy NguyenJul 8, 2013
  8. Thomas GummererJul 8, 2013
  9. Duy NguyenJul 8, 2013
  10. Thomas GummererJul 8, 2013
  11. Duy NguyenJul 8, 2013
  12. Thomas GummererJul 8, 2013
  13. 5/22 Add documentation for the index apiThomas Gummerer, Jul 8, 2013
  14. Duy NguyenJul 9, 2013
  15. Thomas GummererJul 9, 2013
  16. Duy NguyenJul 10, 2013
  17. Thomas GummererJul 11, 2013
  18. Duy NguyenJul 11, 2013
  19. Duy NguyenJul 11, 2013
  20. Junio C HamanoJul 8, 2013
  21. Thomas GummererJul 8, 2013
  22. Junio C HamanoJul 8, 2013
  23. Thomas GummererJul 9, 2013
  24. 06/22 make sure partially read index is not changedThomas Gummerer, Jul 7, 2013
  25. Junio C HamanoJul 8, 2013
  26. Thomas GummererJul 8, 2013
  27. 07/22 dir.c: use index apiThomas Gummerer, Jul 7, 2013
  28. 08/22 tree.c: use index apiThomas Gummerer, Jul 7, 2013
  29. 09/22 name-hash.c: use index apiThomas Gummerer, Jul 7, 2013
  30. 10/22 grep.c: Use index apiThomas Gummerer, Jul 7, 2013
  31. 11/22 ls-files.c: use the index apiThomas Gummerer, Jul 7, 2013
  32. 12/22 read-cache: make read_blob_data_from_index use index apiThomas Gummerer, Jul 7, 2013
  33. 13/22 documentation: add documentation of the index-v5 file formatThomas Gummerer, Jul 7, 2013
  34. Duy NguyenJul 11, 2013
  35. Thomas GummererJul 11, 2013
  36. Duy NguyenJul 11, 2013
  37. Thomas GummererJul 11, 2013
  38. Duy NguyenJul 11, 2013
  39. 14/22 read-cache: make in-memory format aware of stat_crcThomas Gummerer, Jul 7, 2013
  40. 15/22 read-cache: read index-v5Thomas Gummerer, Jul 7, 2013
  41. Eric SunshineJul 7, 2013
  42. Thomas GummererJul 8, 2013
  43. 16/22 read-cache: read resolve-undo dataThomas Gummerer, Jul 7, 2013
  44. 17/22 read-cache: read cache-tree in index-v5Thomas Gummerer, Jul 7, 2013
  45. Eric SunshineJul 7, 2013
  46. 18/22 read-cache: write index-v5Thomas Gummerer, Jul 7, 2013
  47. Eric SunshineJul 7, 2013
  48. 19/22 read-cache: write index-v5 cache-tree dataThomas Gummerer, Jul 7, 2013
  49. 20/22 read-cache: write resolve-undo data for index-v5Thomas Gummerer, Jul 7, 2013
  50. 21/22 update-index.c: rewrite index when index-version is givenThomas Gummerer, Jul 7, 2013
  51. 22/22 p0003-index.sh: add perf test for the index formatsThomas Gummerer, Jul 7, 2013

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