[PATCH v1 00/11] exfat: improve sync dentry

[yuezhang.mo@foxmail.com]

From: Yuezhang Mo <Yuezhang.Mo@sony.com>

This patch set changes sync dentry-by-dentry to sync
dentrySet-by-dentrySet, and remove some syncs that do not cause
data loss. It not only improves the performance of sync dentry,
but also reduces the consumption of storage device life.

I used the following commands and blktrace to measure the improvements
on a class 10 SDXC card.

rm -fr $mnt/dir; mkdir $mnt/dir; sync
time (for ((i=0;i<1000;i++));do touch $mnt/dir/${prefix}$i;done;sync $mnt)
time (for ((i=0;i<1000;i++));do rm $mnt/dir/${prefix}$i;done;sync $mnt)

| case | name len |       create          |        unlink          |
|      |          | time     | write size | time      | write size |
|------+----------+----------+------------+-----------+------------|
|  1   | 15       | 10.260s  | 191KiB     | 9.829s    | 96KiB      |
|  2   | 15       | 11.456s  | 562KiB     | 11.032s   | 562KiB     |
|  3   | 15       | 30.637s  | 3500KiB    | 21.740s   | 2000KiB    |
|  1   | 120      | 10.840s  | 644KiB     | 9.961s    | 315KiB     |
|  2   | 120      | 13.282s  | 1092KiB    | 12.432s   | 752KiB     |
|  3   | 120      | 45.393s  | 7573KiB    | 37.395s   | 5500KiB    |
|  1   | 255      | 11.549s  | 1028KiB    | 9.994s    | 594KiB     |
|  2   | 255      | 15.826s  | 2170KiB    | 13.387s   | 1063KiB    |
|  3   | 255      | 1m7.211s | 12335KiB   | 0m58.517s | 10004KiB   |

case 1. disable dirsync
case 2. with this patch set and enable dirsync
case 3. without this patch set and enable dirsync

Yuezhang Mo (11):
  exfat: add __exfat_get_dentry_set() helper
  exfat: add exfat_get_empty_dentry_set() helper
  exfat: covert exfat_find_empty_entry() to use dentry cache
  exfat: covert exfat_add_entry() to use dentry cache
  exfat: covert exfat_remove_entries() to use dentry cache
  exfat: move free cluster out of exfat_init_ext_entry()
  exfat: covert exfat_init_ext_entry() to use dentry cache
  exfat: remove __exfat_find_empty_entry()
  exfat: remove unused functions
  exfat: do not sync parent dir if just update timestamp
  exfat: remove duplicate update parent dir

 fs/exfat/dir.c      | 286 ++++++++++++++++++-----------------
 fs/exfat/exfat_fs.h |  23 ++-
 fs/exfat/inode.c    |   2 +-
 fs/exfat/namei.c    | 352 +++++++++++++++++---------------------------
 4 files changed, 288 insertions(+), 375 deletions(-)

-- 
2.25.1