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xfsprogs: metadump: move duplicate name handling into its own function

PATCH In review Alex Elder 2 participants 4 messages Feb 18, 2011 – Mar 3, 2011

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Alex Elder

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#0 lore raw

PATCH v3 13/16 xfsprogs: metadump: move duplicate name handling into its own function

Move the handling of duplicate names into its own function. As a result, all names other than "lost+found" files (not just those that get obfuscated) will be checked to avoid duplication.

This makes the local buffer newname[] in generate_obfuscated_name() unnecessary, so just drop it and use the passed-in name.

This is a new change, not posted with this series previously.

---
 db/metadump.c |   95 +++++++++++++++++++++++++++++-----------------------------
 1 file changed, 49 insertions(+), 46 deletions(-)
db/metadump.c +49 -46
Index: b/db/metadump.c
===================================================================
@@ -469,6 +469,37 @@ in_lost_found(
 }
 
 /*
+ * Look up the given name in the name table.  If it is already
+ * present, find an alternate and attempt to use that name instead.
+ *
+ * Returns 1 if the (possibly modified) name is not present in the
+ * name table.  Returns 0 otherwise.
+ */
+static int
+handle_duplicates(xfs_dahash_t hash, size_t name_len, uchar_t *name)
+{
+	int	dup = 0;
+
+	if (!nametable_find(hash, name_len, name))
+	    	return 1;	/* Not already in table */
+
+	/* Name is already in use.  Need to find an alternate. */
+
+	do {
+		obfuscate_name(hash, name_len, name);
+
+		/*
+		 * Search the name table to be sure we don't produce
+		 * a name that's already been used.
+		 */
+		if (!nametable_find(hash, name_len, name))
+			break;
+	} while (++dup < DUP_MAX);
+
+	return dup < DUP_MAX ? 1 : 0;
+}
+
+/*
  * Given a name and its hash value, massage the name in such a way
  * that the result is another name of equal length which shares the
  * same hash value.
@@ -549,9 +580,6 @@ generate_obfuscated_name(
 	uchar_t			*name)
 {
 	xfs_dahash_t		hash;
-	int			dup = 0;
-	uchar_t			newname[NAME_MAX];
-	uchar_t			*newp;
 
 	/*
 	 * We don't obfuscate "lost+found" or any orphan files
@@ -562,58 +590,33 @@ generate_obfuscated_name(
 	if (ino && in_lost_found(ino, namelen, name))
 		return;
 
-	/*
-	 * If the name starts with a slash, just skip over it.  We
-	 * will copy our obfuscated name back into space following
-	 * the slash when we're done.  Our new name will not have
-	 * the '/', and that's the version we'll keep in our
-	 * duplicates table.  Note that the namelen value passed in
-	 * does not include the leading slash (if any).
-	 */
 	if (*name == '/')
-	    	name++;
+	    	name++;		/* Skip over leading slash (if any). */
 
 	hash = libxfs_da_hashname(name, namelen);
-	do {
-		obfuscate_name(hash, namelen, newname);
-
-		/*
-		 * Search the name table to be sure we don't produce
-		 * a name that's already been used.
-		 */
-		if (!nametable_find(hash, namelen, newname))
-			break;
-	} while (++dup < DUP_MAX);
-
-	/* Use the original name if we got too many dups. */
-
-	newp = dup < DUP_MAX ? newname : name;
+	obfuscate_name(hash, namelen, name);
 
 	/*
-	 * Create an entry for the name in the name table.  Use the
-	 * original name if we got too many dups.
+	 * Make sure the name is not something already seen.  If
+	 * this fails we're dealing with a very pathological
+	 * situation, and we'll end up creating an entry with a
+	 * duplicate name, so issue a warning.
 	 */
-	if (!nametable_add(hash, namelen, newp))
+	if (!handle_duplicates(hash, namelen, name)) {
+		print_warning("duplicate name \"%s\" for inode %llu"
+				" in dir inode %llu\n",
+			name, (unsigned long long) ino,
+			(unsigned long long) cur_ino);
 		return;
+	}
 
-	/*
-	 * Update the caller's copy with the obfuscated name.
-	 *
-	 * If we couldn't come up with one, warn if we managed to
-	 * previously create an obfuscated name that matches the one
-	 * we're working on now.
-	 */
-	if (newp != name)
-		memcpy(name, newp, namelen);
-	else if (nametable_find(hash, namelen, name)) {
-		/* Ensure the name we report is NUL-terminated. */
-	    	memcpy(newname, name, namelen);
-	    	newname[namelen] = '\0';
-		print_warning("duplicate name \"%s\" for inode %llu "
-				"in dir inode %llu\n",
-			newname, (unsigned long long) ino,
+	/* Create an entry for the name in the name table. */
+
+	if (!nametable_add(hash, namelen, name))
+		print_warning("unable to record name \"%s\" "
+			"for inode %llu in dir inode %llu\n",
+			name, (unsigned long long) ino,
 			(unsigned long long) cur_ino);
-	}
 }
 
 static void

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#1 lore raw
Quoted 10 lines · Alex Elder

Move the handling of duplicate names into its own function. As a result, all names other than "lost+found" files (not just those that get obfuscated) will be checked to avoid duplication.

This makes the local buffer newname[] in generate_obfuscated_name() unnecessary, so just drop it and use the passed-in name.

This is a new change, not posted with this series previously.

Couple of minor comments below.

Quoted 11 lines
---
 db/metadump.c |   95 +++++++++++++++++++++++++++++-----------------------------
 1 file changed, 49 insertions(+), 46 deletions(-)

Index: b/db/metadump.c
===================================================================

db/metadump.c +0 -0
@@ -469,6 +469,37 @@ in_lost_found(
 }

db/metadump.c in_lost_found( · line 479

Quoted 10 lines
db/metadump.c +8 -0
 
 /*
+ * Look up the given name in the name table.  If it is already
+ * present, find an alternate and attempt to use that name instead.
+ *
+ * Returns 1 if the (possibly modified) name is not present in the
+ * name table.  Returns 0 otherwise.
+ */
+static int
+handle_duplicates(xfs_dahash_t hash, size_t name_len, uchar_t *name)

handle_duplicate_name()?

Quoted 41 lines
db/metadump.c +23 -4
+{
+	int	dup = 0;
+
+	if (!nametable_find(hash, name_len, name))
+	    	return 1;	/* Not already in table */
+
+	/* Name is already in use.  Need to find an alternate. */
+
+	do {
+		obfuscate_name(hash, name_len, name);
+
+		/*
+		 * Search the name table to be sure we don't produce
+		 * a name that's already been used.
+		 */
+		if (!nametable_find(hash, name_len, name))
+			break;
+	} while (++dup < DUP_MAX);
+
+	return dup < DUP_MAX ? 1 : 0;
+}
+
+/*
  * Given a name and its hash value, massage the name in such a way
  * that the result is another name of equal length which shares the
  * same hash value.
@@ -549,9 +580,6 @@ generate_obfuscated_name(
 	uchar_t			*name)
 {
 	xfs_dahash_t		hash;
-	int			dup = 0;
-	uchar_t			newname[NAME_MAX];
-	uchar_t			*newp;
 
 	/*
 	 * We don't obfuscate "lost+found" or any orphan files
@@ -562,58 +590,33 @@ generate_obfuscated_name(
 	if (ino && in_lost_found(ino, namelen, name))
 		return;
 
-	/*

db/metadump.c generate_obfuscated_name( · line 594

Quoted 10 lines
db/metadump.c +1 -8
-	 * If the name starts with a slash, just skip over it.  We
-	 * will copy our obfuscated name back into space following
-	 * the slash when we're done.  Our new name will not have
-	 * the '/', and that's the version we'll keep in our
-	 * duplicates table.  Note that the namelen value passed in
-	 * does not include the leading slash (if any).
-	 */
 	if (*name == '/')
-	    	name++;
+	    	name++;		/* Skip over leading slash (if any). */

I think the comment explaining _why_ we are skipping over the slash is much more important than the new comment that just describes what the code is doing. Hence I'd prefer a slightly modified version of the old comment rather than removing it altogether...

Cheers,

Dave.

Signature · 7 lines
Dave Chinner
[email protected]

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author
#2 lore raw

PATCH v4 13/16 xfsprogs: metadump: move duplicate name handling into its own function

Move the handling of duplicate names into its own function. As a result, all names other than "lost+found" files (not just those that get obfuscated) will be checked to avoid duplication.

This makes the local buffer newname[] in generate_obfuscated_name() unnecessary, so just drop it and use the passed-in name.

Updates:
- A comment about handling of a leading '/' character is now modified to match the updated code, rather than being deleted altogether.
- Renamed handle_duplicates() to be handle_duplicate_name().

---
 db/metadump.c |   78
++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 47 insertions(+), 31 deletions(-)
db/metadump.c +9 -0
Index: b/db/metadump.c
===================================================================
@@ -552,6 +552,37 @@ obfuscate_name(
 	ASSERT(libxfs_da_hashname(name, name_len) == hash);
 }
 
+/*
+ * Look up the given name in the name table.  If it is already
+ * present, find an alternate and attempt to use that name instead.
+ *
+ * Returns 1 if the (possibly modified) name is not present in the
+ * name table.  Returns 0 otherwise.
+ */
+static int
+handle_duplicate_name(xfs_dahash_t hash, size_t name_len, uchar_t

*name)
+{
+ int dup = 0;
+
+ if (!nametable_find(hash, name_len, name))
+ return 1; /* Not already in table */
+
+ /* Name is already in use. Need to find an alternate. */
+
+ do {
+ obfuscate_name(hash, name_len, name);
+
+ /*
+ * Search the name table to be sure we don't produce
+ * a name that's already been used.
+ */
+ if (!nametable_find(hash, name_len, name))
+ break;
+ } while (++dup < DUP_MAX);
+
+ return dup < DUP_MAX ? 1 : 0;
+}
+
static void
generate_obfuscated_name(
xfs_ino_t ino,
@@ -559,8 +590,6 @@ generate_obfuscated_name(
uchar_t *name)
{
xfs_dahash_t hash;
- int dup = 0;
- uchar_t newname[NAME_MAX];

/*
* We don't obfuscate "lost+found" or any orphan files
@@ -572,48 +601,35 @@ generate_obfuscated_name(
return;

/*
- * If the name starts with a slash, just skip over it. We
- * will copy our obfuscated name back into space following
- * the slash when we're done. Our new name will not have
- * the '/', and that's the version we'll keep in our
- * duplicates table. Note that the namelen value passed in
- * does not include the leading slash (if any).
+ * If the name starts with a slash, just skip over it. It
+ * isn't included in the hash and we don't record it in the
+ * name table. Note that the namelen value passed in does
+ * not count the leading slash (if one is present).
*/
if (*name == '/')
name++;

- hash = libxfs_da_hashname(name, namelen);
- do {
- obfuscate_name(hash, namelen, newname);
+ /* Obfuscate the name (if possible) */

- /*
- * Search the name table to be sure we don't produce
- * a name that's already been used.
- */
- if (!nametable_find(hash, namelen, newname))
- break;
- } while (++dup < DUP_MAX);
+ hash = libxfs_da_hashname(name, namelen);
+ obfuscate_name(hash, namelen, name);

/*
- * Update the caller's copy with the obfuscated name.
- *
- * If we couldn't come up with one, just use the original
- * name without obfuscation. Issue a warning if we managed
- * to previously create an obfuscated name that matches the
- * one we're working on now.
+ * Make sure the name is not something already seen. If we
+ * fail to find a suitable alternate, we're dealing with a
+ * very pathological situation, and we may end up creating
+ * a duplicate name in the metadump, so issue a warning.
*/
- if (dup < DUP_MAX)
- memcpy(name, newname, namelen);
- else if (nametable_find(hash, namelen, name))
+ if (!handle_duplicate_name(hash, namelen, name)) {
print_warning("duplicate name for inode %llu "
"in dir inode %llu\n",
(unsigned long long) ino, (unsigned long long) cur_ino);
+ return;
+ }
+
+ /* Create an entry for the new name in the name table. */

- /*
- * Create an entry for the name in the name table. Use the
- * original name if we got too many dups.
- */
if (!nametable_add(hash, namelen, name))
print_warning("unable to record name for inode %llu "
"in dir inode %llu\n",

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Reviewed-by on v4 13/16
#3 lore raw
Quoted 7 lines · Alex Elder

Move the handling of duplicate names into its own function. As a result, all names other than "lost+found" files (not just those that get obfuscated) will be checked to avoid duplication.

This makes the local buffer newname[] in generate_obfuscated_name() unnecessary, so just drop it and use the passed-in name.

Quoted 6 lines

Updates:
- A comment about handling of a leading '/' character is now modified to match the updated code, rather than being deleted altogether.
- Renamed handle_duplicates() to be handle_duplicate_name().

Signature · 7 lines
Dave Chinner
[email protected]

_______________________________________________
xfs mailing list
[email protected]
http://oss.sgi.com/mailman/listinfo/xfs