2012-12-11 06:40:02

by Tao Ma

Subject: [PATCH] ext4: Add EXT4_ZERO_XATTR_VALUE to init inline data directly.

From: Tao Ma <[email protected]>

Build rebot found this error:

config: make ARCH=sparc allyesconfig

All error/warnings:

fs/ext4/inline.c: In function 'ext4_create_inline_data':
fs/ext4/inline.c:268:19: error: 'empty_zero_page' undeclared (first use in this function)
fs/ext4/inline.c:268:19: note: each undeclared identifier is reported only once for each function it appears in
fs/ext4/inline.c: At top level:
fs/ext4/inline.c:164:12: warning: 'ext4_read_inline_data' defined but not used [-Wunused-function]

In sparc, it seems that we don't have empty_zero_page, so add a new specific
value EXT4_ZERO_XATTR_VALUE so that when ext4_xattr_set_entry see this flag
memset the space directly instead of copying from value. This idea is
inspired by Theodore Ts'o.

Cc: "Theodore Ts'o" <[email protected]>
Signed-off-by: Tao Ma <[email protected]>
---
fs/ext4/inline.c | 2 +-
fs/ext4/xattr.c | 22 ++++++++++++++++------
fs/ext4/xattr.h | 1 +
3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 6b600b4..e435343 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -263,7 +263,7 @@ static int ext4_create_inline_data(handle_t *handle,
goto out;

if (len > EXT4_MIN_INLINE_DATA_SIZE) {
- value = (void *)empty_zero_page;
+ value = EXT4_ZERO_XATTR_VALUE;
len -= EXT4_MIN_INLINE_DATA_SIZE;
} else {
value = "";
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 2251769..3a91ebc 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -628,9 +628,14 @@ ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s)
size. Just replace. */
s->here->e_value_size =
cpu_to_le32(i->value_len);
- memset(val + size - EXT4_XATTR_PAD, 0,
- EXT4_XATTR_PAD); /* Clear pad bytes. */
- memcpy(val, i->value, i->value_len);
+ if (i->value == EXT4_ZERO_XATTR_VALUE) {
+ memset(val, 0, size);
+ } else {
+ /* Clear pad bytes first. */
+ memset(val + size - EXT4_XATTR_PAD, 0,
+ EXT4_XATTR_PAD);
+ memcpy(val, i->value, i->value_len);
+ }
return 0;
}

@@ -669,9 +674,14 @@ ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s)
size_t size = EXT4_XATTR_SIZE(i->value_len);
void *val = s->base + min_offs - size;
s->here->e_value_offs = cpu_to_le16(min_offs - size);
- memset(val + size - EXT4_XATTR_PAD, 0,
- EXT4_XATTR_PAD); /* Clear the pad bytes. */
- memcpy(val, i->value, i->value_len);
+ if (i->value == EXT4_ZERO_XATTR_VALUE) {
+ memset(val, 0, size);
+ } else {
+ /* Clear the pad bytes first. */
+ memset(val + size - EXT4_XATTR_PAD, 0,
+ EXT4_XATTR_PAD);
+ memcpy(val, i->value, i->value_len);
+ }
}
}
return 0;
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index c33fa41..17a6e44 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -71,6 +71,7 @@ struct ext4_xattr_entry {
#define BFIRST(bh) ENTRY(BHDR(bh)+1)
#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)

+#define EXT4_ZERO_XATTR_VALUE ((void *)-1)

struct ext4_xattr_info {
int name_index;
--
1.7.0.4

2012-12-11 08:33:37

by Theodore Ts'o

Subject: Re: ext4: Add EXT4_ZERO_XATTR_VALUE to init inline data directly.

Thanks, applied with a somewhat edited commit description:

ext4: zero out inline data using memset() instead of empty_zero_page

Not all architectures (in particular, sparc64) have empty_zero_page.
So instead of copying from empty_zero_page, use memset to clear the
inline data by signalling to ext4_xattr_set_entry() via a magic
pointer value, EXT4_ZERO_ATTR_VALUE, which is defined by casting -1 to
a pointer.

This fixes a build failure on sparc64, and the memset() should be more
efficient than using memcpy() anyway.

Signed-off-by: Tao Ma <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>

- Ted