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| author | Eric Sandeen <sandeen@redhat.com> | 2009-07-13 10:24:17 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2009-07-13 10:24:17 -0400 |
| commit | 726447d803802cd0be8f62d17c4a34421781b938 (patch) | |
| tree | ef1d7d4b9afb0f81b9eb6f09980c152d35ceb3cf | |
| parent | 089ceecc1ea4a69ed8bcc5c7c7b96ce487e26b33 (diff) | |
| download | op-kernel-dev-726447d803802cd0be8f62d17c4a34421781b938.zip op-kernel-dev-726447d803802cd0be8f62d17c4a34421781b938.tar.gz | |
ext4: naturally align struct ext4_allocation_request
As Ted noted, the ext4_allocation_request isn't well aligned. Looking
at it with pahole we're wasting space on 64-bit arches:
struct ext4_allocation_request {
struct inode * inode; /* 0 8 */
ext4_lblk_t logical; /* 8 4 */
/* XXX 4 bytes hole, try to pack */
ext4_fsblk_t goal; /* 16 8 */
ext4_lblk_t lleft; /* 24 4 */
/* XXX 4 bytes hole, try to pack */
ext4_fsblk_t pleft; /* 32 8 */
ext4_lblk_t lright; /* 40 4 */
/* XXX 4 bytes hole, try to pack */
ext4_fsblk_t pright; /* 48 8 */
unsigned int len; /* 56 4 */
unsigned int flags; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
/* size: 64, cachelines: 1, members: 9 */
/* sum members: 52, holes: 3, sum holes: 12 */
};
Grouping 32-bit members together closes these holes and shrinks the
structure by 12 bytes. which is important since ext4 can get on the
hairy edge of stack overruns.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/ext4.h | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 0ddf7e5..9714db3 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -93,20 +93,20 @@ typedef unsigned int ext4_group_t; struct ext4_allocation_request { /* target inode for block we're allocating */ struct inode *inode; + /* how many blocks we want to allocate */ + unsigned int len; /* logical block in target inode */ ext4_lblk_t logical; - /* phys. target (a hint) */ - ext4_fsblk_t goal; /* the closest logical allocated block to the left */ ext4_lblk_t lleft; - /* phys. block for ^^^ */ - ext4_fsblk_t pleft; /* the closest logical allocated block to the right */ ext4_lblk_t lright; - /* phys. block for ^^^ */ + /* phys. target (a hint) */ + ext4_fsblk_t goal; + /* phys. block for the closest logical allocated block to the left */ + ext4_fsblk_t pleft; + /* phys. block for the closest logical allocated block to the right */ ext4_fsblk_t pright; - /* how many blocks we want to allocate */ - unsigned int len; /* flags. see above EXT4_MB_HINT_* */ unsigned int flags; }; |
