Hi,
On 3/19/21 6:53 PM, Sungjong Seo wrote:
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?
Agreed.
What I want to change here is very clear and any way to achieve the goal
would be good.
+ * @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".
Yes, but we would not need this backup any more.
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.
OK. I thought this routine is more straightforward to understand what is
being done here.
But I don't have any strong opinion about this, so I'll change in that way.
BTW, I think we can do this without local variable.
