From: Andreas Gruenbacher <agruen@suse.de>

It is common to update extended attributes without changing the value's
length. This patch optimizes this case. In addition to that, the current
code tries to recognize early when extended attribute blocks become
empty. This optimization is not of significant value, so this patch
removes it, and moves the empty block test further down.



 fs/ext2/xattr.c |   42 ++++++++++++++++++++++++++----------------
 fs/ext3/xattr.c |   43 ++++++++++++++++++++++++++-----------------
 2 files changed, 52 insertions(+), 33 deletions(-)

diff -puN fs/ext2/xattr.c~xattr-just-replace fs/ext2/xattr.c
--- 25/fs/ext2/xattr.c~xattr-just-replace	2003-07-02 16:37:29.000000000 -0700
+++ 25-akpm/fs/ext2/xattr.c	2003-07-02 16:37:29.000000000 -0700
@@ -643,13 +643,24 @@ bad_block:		ext2_error(sb, "ext2_xattr_s
 		here->e_name_len = name_len;
 		memcpy(here->e_name, name, name_len);
 	} else {
-		/* Remove the old value. */
 		if (!here->e_value_block && here->e_value_size) {
 			char *first_val = (char *)header + min_offs;
 			size_t offs = le16_to_cpu(here->e_value_offs);
 			char *val = (char *)header + offs;
 			size_t size = EXT2_XATTR_SIZE(
 				le32_to_cpu(here->e_value_size));
+
+			if (size == EXT2_XATTR_SIZE(value_len)) {
+				/* The old and the new value have the same
+				   size. Just replace. */
+				here->e_value_size = cpu_to_le32(value_len);
+				memset(val + size - EXT2_XATTR_PAD, 0,
+				       EXT2_XATTR_PAD); /* Clear pad bytes. */
+				memcpy(val, value, value_len);
+				goto skip_replace;
+			}
+
+			/* Remove the old value. */
 			memmove(first_val + size, first_val, val - first_val);
 			memset(first_val, 0, size);
 			here->e_value_offs = 0;
@@ -666,19 +677,12 @@ bad_block:		ext2_error(sb, "ext2_xattr_s
 			}
 		}
 		if (value == NULL) {
-			/* Remove this attribute. */
-			if (EXT2_XATTR_NEXT(ENTRY(header+1)) == last) {
-				/* This block is now empty. */
-				error = ext2_xattr_set2(inode, bh, NULL);
-				goto cleanup;
-			} else {
-				/* Remove the old name. */
-				size_t size = EXT2_XATTR_LEN(name_len);
-				last = ENTRY((char *)last - size);
-				memmove(here, (char*)here + size,
-					(char*)last - (char*)here);
-				memset(last, 0, size);
-			}
+			/* Remove the old name. */
+			size_t size = EXT2_XATTR_LEN(name_len);
+			last = ENTRY((char *)last - size);
+			memmove(here, (char*)here + size,
+				(char*)last - (char*)here);
+			memset(last, 0, size);
 		}
 	}
 
@@ -695,9 +699,15 @@ bad_block:		ext2_error(sb, "ext2_xattr_s
 			memcpy(val, value, value_len);
 		}
 	}
-	ext2_xattr_rehash(header, here);
 
-	error = ext2_xattr_set2(inode, bh, header);
+skip_replace:
+	if (IS_LAST_ENTRY(ENTRY(header+1))) {
+		/* This block is now empty. */
+		error = ext2_xattr_set2(inode, bh, NULL);
+	} else {
+		ext2_xattr_rehash(header, here);
+		error = ext2_xattr_set2(inode, bh, header);
+	}
 
 cleanup:
 	brelse(bh);
diff -puN fs/ext3/xattr.c~xattr-just-replace fs/ext3/xattr.c
--- 25/fs/ext3/xattr.c~xattr-just-replace	2003-07-02 16:37:29.000000000 -0700
+++ 25-akpm/fs/ext3/xattr.c	2003-07-02 16:37:29.000000000 -0700
@@ -644,13 +644,24 @@ bad_block:		ext3_error(sb, "ext3_xattr_s
 		here->e_name_len = name_len;
 		memcpy(here->e_name, name, name_len);
 	} else {
-		/* Remove the old value. */
 		if (!here->e_value_block && here->e_value_size) {
 			char *first_val = (char *)header + min_offs;
 			size_t offs = le16_to_cpu(here->e_value_offs);
 			char *val = (char *)header + offs;
 			size_t size = EXT3_XATTR_SIZE(
 				le32_to_cpu(here->e_value_size));
+
+			if (size == EXT3_XATTR_SIZE(value_len)) {
+				/* The old and the new value have the same
+				   size. Just replace. */
+				here->e_value_size = cpu_to_le32(value_len);
+				memset(val + size - EXT3_XATTR_PAD, 0,
+				       EXT3_XATTR_PAD); /* Clear pad bytes. */
+				memcpy(val, value, value_len);
+				goto skip_replace;
+			}
+
+			/* Remove the old value. */
 			memmove(first_val + size, first_val, val - first_val);
 			memset(first_val, 0, size);
 			here->e_value_offs = 0;
@@ -667,20 +678,12 @@ bad_block:		ext3_error(sb, "ext3_xattr_s
 			}
 		}
 		if (value == NULL) {
-			/* Remove this attribute. */
-			if (EXT3_XATTR_NEXT(ENTRY(header+1)) == last) {
-				/* This block is now empty. */
-				error = ext3_xattr_set_handle2(handle, inode,
-							       bh, NULL);
-				goto cleanup;
-			} else {
-				/* Remove the old name. */
-				size_t size = EXT3_XATTR_LEN(name_len);
-				last = ENTRY((char *)last - size);
-				memmove(here, (char*)here + size,
-					(char*)last - (char*)here);
-				memset(last, 0, size);
-			}
+			/* Remove the old name. */
+			size_t size = EXT3_XATTR_LEN(name_len);
+			last = ENTRY((char *)last - size);
+			memmove(here, (char*)here + size,
+				(char*)last - (char*)here);
+			memset(last, 0, size);
 		}
 	}
 
@@ -697,9 +700,15 @@ bad_block:		ext3_error(sb, "ext3_xattr_s
 			memcpy(val, value, value_len);
 		}
 	}
-	ext3_xattr_rehash(header, here);
 
-	error = ext3_xattr_set_handle2(handle, inode, bh, header);
+skip_replace:
+	if (IS_LAST_ENTRY(ENTRY(header+1))) {
+		/* This block is now empty. */
+		error = ext3_xattr_set_handle2(handle, inode, bh, NULL);
+	} else {
+		ext3_xattr_rehash(header, here);
+		error = ext3_xattr_set_handle2(handle, inode, bh, header);
+	}
 
 cleanup:
 	brelse(bh);

_