> When directory iterate and lookup is called, there's a buggy rewinding of
> start point for traversing cluster chain to the parent directory entry's
> first cluster. This caused repeated cluster chain traversing from the
> first entry of the parent directory that would show worse performance if
> huge amounts of files exist under the parent directory.
> Fix not to rewind, make continue from currently referenced cluster and dir
> entry.
>
> Tested with 50,000 files under single directory / 256GB sdcard, with
> command "time ls -l > /dev/null",
> Before : 0m08.69s real 0m00.27s user 0m05.91s system
> After : 0m07.01s real 0m00.25s user 0m04.34s system
>
> Signed-off-by: Hyeongseok Kim <hyeongseok@xxxxxxxxx>
> ---
> fs/exfat/dir.c | 39 ++++++++++++++++++++++++++++++++-------
> fs/exfat/exfat_fs.h | 2 +-
> fs/exfat/namei.c | 6 ++++--
> 3 files changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index
> e1d5536de948..63f08987a8fe 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -147,7 +147,7 @@ static int exfat_readdir(struct inode *inode, loff_t
> *cpos, struct exfat_dir_ent
[snip]
> + * @de: If p_uniname is found, filled with optimized dir/entry
> + * for traversing cluster chain. Basically,
> + * (p_dir.dir+return entry) and (de.dir.dir+de.entry) are
> + * pointing the same physical directory entry, but if
> + * caller needs to start to traverse cluster chain,
> + * it's better option to choose the information in de.
> + * Caller could only trust .dir and .entry field.
exfat-fs has exfat_hint structure for keeping clusters and entries as hints.
Of course, the caller, exfat_find(), should adjust exfat_chain with
hint value just before calling exfat_get_dentry_set() as follows.
/* adjust cdir to the optimized value */
cdir.dir = hint_opt.clu;
if (cdir.flag & ALLOC_NO_FAT_CHAIN) {
cdir.size -= dentry / sbi->dentries_per_clu;
dentry = hint_opt.eidx;
What do you think about using it?
> + * @return:
> + * >= 0: file directory entry position where the name exists
> + * -ENOENT: entry with the name does not exist
> + * -EIO: I/O error
> */
[snip]
> @@ -1070,11 +1081,14 @@ int exfat_find_dir_entry(struct super_block *sb,
> struct exfat_inode_info *ei,
> }
>
> if (clu.flags == ALLOC_NO_FAT_CHAIN) {
> - if (--clu.size > 0)
> + if (--clu.size > 0) {
> + exfat_chain_dup(&de->dir, &clu);
If you want to make a backup of the clu, it seems more appropriate to move
exfat_chain_dup() right above the "if".
> clu.dir++;
> + }
> else
> clu.dir = EXFAT_EOF_CLUSTER;
> } else {
> + exfat_chain_dup(&de->dir, &clu);
> if (exfat_get_next_cluster(sb, &clu.dir))
> return -EIO;
> }
> @@ -1101,6 +1115,17 @@ int exfat_find_dir_entry(struct super_block *sb,
> struct exfat_inode_info *ei,
> return -ENOENT;
>
> found:
> + /* set as dentry in cluster */
> + de->entry = (dentry - num_ext) & (dentries_per_clu - 1);
> + /*
> + * if dentry_set spans to the next_cluster,
> + * e.g. (de->entry + num_ext + 1 > dentries_per_clu)
> + * current de->dir is correct which have previous cluster info,
> + * but if it doesn't span as below, "clu" is correct, so update.
> + */
> + if (de->entry + num_ext + 1 <= dentries_per_clu)
> + exfat_chain_dup(&de->dir, &clu);
> +
Let it be simple.
1. Keep an old value in the stack variable, when it found a FILE or DIR
entry.
2. And just copy that here.
There are more assignments, but I think its impact might be negligible.
Thanks.
