Re: [PATCH][FAT] FAT dirent scan with hin take #3

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Hi,

Thank you checking code...

Pekka Enberg wrote:
Hi,

	:
	snip


This patch enables using hint information on scanning dir.
It achieves excellent performance with "ls -l" for over 1000 entries.

* fat-dirscan-with-hint_3.patch for linux 2.6.13

fs/fat/dir.c             |  130 ++++++++++++++++++++++++++++++++++++++++++++---
fs/fat/inode.c           |   13 ++++
include/linux/msdos_fs.h |    2
3 files changed, 137 insertions(+), 8 deletions(-)

Signed-off-by: Hiroyuki Machida <[email protected]> for CELF

* modified files


--- linux-2.6.13/fs/fat/dir.c   2005-08-29 08:41:01.000000000 +0900
+++ linux-2.6.13-work/fs/fat/dir.c      2005-08-31 13:48:01.001119437 +0900
@@ -201,6 +201,88 @@ fat_shortname2uni(struct nls_table *nls,
 * Return values: negative -> error, 0 -> not found, positive -> found,
 * value is the total amount of slots, including the shortname entry.
 */
+
+#define FAT_SCAN_SHIFT 4                       /* 2x8 way scan hints  */
+#define FAT_SCAN_NWAY  (1<<FAT_SCAN_SHIFT)
+
+inline
+static int hint_allocate(struct inode *dir)
+{
+       loff_t *hints;
+       int err = 0;
+
+       if (!MSDOS_I(dir)->scan_hints) {


Please consider moving this check to callers. Conditional allocation
makes this bit strange API-wise. Or alternatively, give
hint_allocate() a better name.

How about hint_allocate_conditional() ?


--- linux-2.6.13/fs/fat/inode.c 2005-08-29 08:41:01.000000000 +0900
+++ linux-2.6.13-work/fs/fat/inode.c    2005-08-31 12:59:54.292274060 +0900
@@ -242,6 +242,8 @@ static int fat_fill_inode(struct inode *
       inode->i_version++;
       inode->i_generation = get_seconds();

+       init_MUTEX(&MSDOS_I(inode)->scan_lock);
+       MSDOS_I(inode)->scan_hints = 0;


Please use NULL.

Ok,


       if ((de->attr & ATTR_DIR) && !IS_FREE(de->name)) {
               inode->i_generation &= ~1;
               inode->i_mode = MSDOS_MKMODE(de->attr,
@@ -345,6 +347,15 @@ static void fat_delete_inode(struct inod
static void fat_clear_inode(struct inode *inode)
{
       struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+       loff_t *hints;
+
+       down(&MSDOS_I(inode)->scan_lock);
+       hints = (MSDOS_I(inode)->scan_hints);


Pleas drop redundant parenthesis.

Ok,


+       if (hints) {
+               MSDOS_I(inode)->scan_hints = NULL;
+       }
+       up(&MSDOS_I(inode)->scan_lock);
+       kfree(hints);


Why can't you do kfree() under scan_lock?

Just try to minimize blocked period.



@@ -1011,6 +1022,8 @@ static int fat_read_root(struct inode *i
       struct msdos_sb_info *sbi = MSDOS_SB(sb);
       int error;

+       init_MUTEX(&MSDOS_I(inode)->scan_lock);
+       MSDOS_I(inode)->scan_hints = 0;


Please use NULL here.

Ok.

                             Pekka
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--
Hiroyuki Machida		[email protected]		
SSW Dept. HENC, Sony Corp.
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