On Fri, Nov 11, 2011 at 10:58:11AM +0000, Steven Whitehouse wrote:
> Hi,
>
> On Thu, 2011-11-10 at 18:34 +0800, Zheng Liu wrote:
> > From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> >
> > A per-cpu counter is defined to store io types in ext4. We define 10 io types
> > in ext4, which includes 9 metadata types and 1 data type. Read and write
> > operations are counted separately. When checks 'Issue' flag, filesystem needs
> > to lock buffer.
> >
> > Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> > Signed-off-by: Wang Shaoyan <wangshaoyan.pt@xxxxxxxxxx>
> > ---
> > fs/ext4/ext4.h | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> > fs/ext4/super.c | 19 +++++++++++++++++++
> > 2 files changed, 72 insertions(+), 0 deletions(-)
> >
> > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> > index 5b0e26a..39a1495 100644
> > --- a/fs/ext4/ext4.h
> > +++ b/fs/ext4/ext4.h
> > @@ -1108,6 +1108,23 @@ struct ext4_super_block {
> > #define EXT4_MF_FS_ABORTED 0x0002 /* Fatal error detected */
> >
> > /*
> > + * ext4 io types
> > + */
> > +enum {
> > + EXT4_IOS_SUPER_BLOCK = 0,
> > + EXT4_IOS_GROUP_DESC,
> > + EXT4_IOS_INODE_BITMAP,
> > + EXT4_IOS_BLOCK_BITMAP,
> > + EXT4_IOS_INODE_TABLE,
> > + EXT4_IOS_EXTENT_BLOCK,
> > + EXT4_IOS_INDIRECT_BLOCK,
> > + EXT4_IOS_DIR_ENTRY,
> > + EXT4_IOS_EXTENDED_ATTR,
> > + EXT4_IOS_REGULAR_DATA,
> > + EXT4_IOS_TYPE_END,
> > +};
> > +
> > +/*
> > * fourth extended-fs super-block data in memory
> > */
> > struct ext4_sb_info {
> > @@ -1284,6 +1301,11 @@ static inline void ext4_set_io_unwritten_flag(struct inode *inode,
> > }
> > }
> >
> > +static inline unsigned ext4_blocks_per_page(struct inode *inode)
> > +{
> > + return PAGE_CACHE_SIZE >> inode->i_blkbits;
> > +}
> > +
> > /*
> > * Inode dynamic state flags
> > */
> > @@ -1926,6 +1948,37 @@ extern int ext4_group_extend(struct super_block *sb,
> > ext4_fsblk_t n_blocks_count);
> >
> > /* super.c */
> > +extern void __ext4_io_stat(int, int, unsigned long);
> > +#define ext4_ios_read(bh, type, count) \
> > + do { \
> > + if (!bh) \
> > + break; \
> > + lock_buffer(bh); \
> > + if (buffer_issue(bh)) { \
> > + clear_buffer_issue(bh); \
> > + __ext4_io_stat(READ, type, count); \
> > + } \
> > + unlock_buffer(bh); \
> > + } while (0)
> Why not just test_and_clear_bit(BH_Issue) ? I don't follow why the
> buffer needs to be locked and unlocked,
test_and_clear_bit(BH_Issue) is better. Calling lock/unlock_buffer() is
to ensure 'Issue' flag can be set or cleared atomically. It is
unnecessary after using test_and_clear_bit(BH_Issue).
Regards,
Zheng
>
> Steve.
>
>
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