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Message-ID: <tencent_316CDC61E3A3AE54E74179695FD15D214508@qq.com>
Date: Thu, 3 Jul 2025 17:54:38 +0800
From: Yuwen Chen <ywen.chen@...mail.com>
To: ywen.chen@...mail.com
Cc: adilger.kernel@...ger.ca,
brauner@...nel.org,
chao@...nel.org,
jaegeuk@...nel.org,
linux-ext4@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
tytso@....edu,
viro@...iv.linux.org.uk
Subject: [PATCH v2] f2fs: improve the performance of f2fs_lookup
On the Android system, the file creation operation will call
the f2fs_lookup function. When there are too many files in a
directory, the generic_ci_match operation will be called
repeatedly in large quantities. In extreme cases, the file
creation speed will drop to three times per second.
Use the following program to conduct a file-creation test in
the private program directory(/data/media/0/Android/data/*)
of Android.
int main(int argc, char **argv)
{
size_t fcnt = 0;
char path[PATH_MAX];
char buf[4096] = {0};
int i, fd;
if (argc < 2)
return - EINVAL;
fcnt = atoi(argv[1]);
for (i = 0; i < fcnt; i++)
{
snprintf(path, sizeof(path), "./%d", i);
fd = open(path, O_RDWR | O_CREAT, 0600);
if (fd < 0)
return - 1;
write(fd, buf, sizeof(buf));
close(fd);
}
return 0;
}
The test platform is Snapdragon 8s Gen4, with a kernel version
of v6.16 and a userdebug version.
Before this submission was merged, when creating 2000 files,
the performance test results are as follows:
$ time /data/file_creater 2000
0m14.83s real 0m00.00s user 0m14.30s system
0m15.61s real 0m00.00s user 0m15.04s system
0m14.72s real 0m00.01s user 0m14.18s system
After this submission was merged, the performance is as follows:
$ time /data/file_creater 2000
0m08.17s real 0m00.00s user 0m07.86s system
0m08.16s real 0m00.01s user 0m07.86s system
0m08.15s real 0m00.00s user 0m07.86s system
It was observed through perf that the generic_ci_match function
was called a large number of times, which led to most of the
time being spent on memory allocation and release. Due to a
flush_dcache operation in the implementation of cts_cbc_decrypt,
this memory cannot be allocated on the stack.
Signed-off-by: Yuwen Chen <ywen.chen@...mail.com>
---
fs/ext4/namei.c | 2 +-
fs/f2fs/dir.c | 24 +++++++++++++++++-------
fs/f2fs/f2fs.h | 3 ++-
fs/f2fs/inline.c | 3 ++-
fs/libfs.c | 32 +++++++++++++++++++++++++++++---
include/linux/fs.h | 8 +++++++-
6 files changed, 58 insertions(+), 14 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index a178ac2294895..f235693bd71aa 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1443,7 +1443,7 @@ static bool ext4_match(struct inode *parent,
return generic_ci_match(parent, fname->usr_fname,
&fname->cf_name, de->name,
- de->name_len) > 0;
+ de->name_len, NULL) > 0;
}
#endif
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index c36b3b22bfffd..ee0cbeb80debd 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -176,6 +176,7 @@ static struct f2fs_dir_entry *find_in_block(struct inode *dir,
struct folio *dentry_folio,
const struct f2fs_filename *fname,
int *max_slots,
+ struct decrypted_name_prealloc *prealloc,
bool use_hash)
{
struct f2fs_dentry_block *dentry_blk;
@@ -184,12 +185,13 @@ static struct f2fs_dir_entry *find_in_block(struct inode *dir,
dentry_blk = folio_address(dentry_folio);
make_dentry_ptr_block(dir, &d, dentry_blk);
- return f2fs_find_target_dentry(&d, fname, max_slots, use_hash);
+ return f2fs_find_target_dentry(&d, fname, max_slots, prealloc, use_hash);
}
static inline int f2fs_match_name(const struct inode *dir,
const struct f2fs_filename *fname,
- const u8 *de_name, u32 de_name_len)
+ const u8 *de_name, u32 de_name_len,
+ struct decrypted_name_prealloc *prealloc)
{
struct fscrypt_name f;
@@ -197,7 +199,7 @@ static inline int f2fs_match_name(const struct inode *dir,
if (fname->cf_name.name)
return generic_ci_match(dir, fname->usr_fname,
&fname->cf_name,
- de_name, de_name_len);
+ de_name, de_name_len, prealloc);
#endif
f.usr_fname = fname->usr_fname;
@@ -210,6 +212,7 @@ static inline int f2fs_match_name(const struct inode *dir,
struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
const struct f2fs_filename *fname, int *max_slots,
+ struct decrypted_name_prealloc *prealloc,
bool use_hash)
{
struct f2fs_dir_entry *de;
@@ -236,7 +239,8 @@ struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
if (!use_hash || de->hash_code == fname->hash) {
res = f2fs_match_name(d->inode, fname,
d->filename[bit_pos],
- le16_to_cpu(de->name_len));
+ le16_to_cpu(de->name_len),
+ prealloc);
if (res < 0)
return ERR_PTR(res);
if (res)
@@ -261,6 +265,7 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
unsigned int level,
const struct f2fs_filename *fname,
struct folio **res_folio,
+ struct decrypted_name_prealloc *prealloc,
bool use_hash)
{
int s = GET_DENTRY_SLOTS(fname->disk_name.len);
@@ -296,7 +301,8 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
}
}
- de = find_in_block(dir, dentry_folio, fname, &max_slots, use_hash);
+ de = find_in_block(dir, dentry_folio, fname, &max_slots, prealloc,
+ use_hash);
if (IS_ERR(de)) {
*res_folio = ERR_CAST(de);
de = NULL;
@@ -336,6 +342,7 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
unsigned int max_depth;
unsigned int level;
bool use_hash = true;
+ struct decrypted_name_prealloc prealloc = {0};
*res_folio = NULL;
@@ -343,7 +350,8 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
start_find_entry:
#endif
if (f2fs_has_inline_dentry(dir)) {
- de = f2fs_find_in_inline_dir(dir, fname, res_folio, use_hash);
+ de = f2fs_find_in_inline_dir(dir, fname, res_folio, &prealloc,
+ use_hash);
goto out;
}
@@ -359,7 +367,8 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
}
for (level = 0; level < max_depth; level++) {
- de = find_in_level(dir, level, fname, res_folio, use_hash);
+ de = find_in_level(dir, level, fname, res_folio, &prealloc,
+ use_hash);
if (de || IS_ERR(*res_folio))
break;
}
@@ -372,6 +381,7 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
goto start_find_entry;
}
#endif
+ kfree(prealloc.name);
/* This is to increase the speed of f2fs_create */
if (!de)
F2FS_I(dir)->task = current;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9333a22b9a01e..dfbd2215310fb 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3673,6 +3673,7 @@ int f2fs_prepare_lookup(struct inode *dir, struct dentry *dentry,
void f2fs_free_filename(struct f2fs_filename *fname);
struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
const struct f2fs_filename *fname, int *max_slots,
+ struct decrypted_name_prealloc *prealloc,
bool use_hash);
int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
unsigned int start_pos, struct fscrypt_str *fstr);
@@ -4316,7 +4317,7 @@ int f2fs_write_inline_data(struct inode *inode, struct folio *folio);
int f2fs_recover_inline_data(struct inode *inode, struct folio *nfolio);
struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
const struct f2fs_filename *fname, struct folio **res_folio,
- bool use_hash);
+ struct decrypted_name_prealloc *prealloc, bool use_hash);
int f2fs_make_empty_inline_dir(struct inode *inode, struct inode *parent,
struct folio *ifolio);
int f2fs_add_inline_entry(struct inode *dir, const struct f2fs_filename *fname,
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 901c630685ced..d02ff6c26d70a 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -353,6 +353,7 @@ int f2fs_recover_inline_data(struct inode *inode, struct folio *nfolio)
struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
const struct f2fs_filename *fname,
struct folio **res_folio,
+ struct decrypted_name_prealloc *prealloc,
bool use_hash)
{
struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
@@ -370,7 +371,7 @@ struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
inline_dentry = inline_data_addr(dir, ifolio);
make_dentry_ptr_inline(dir, &d, inline_dentry);
- de = f2fs_find_target_dentry(&d, fname, NULL, use_hash);
+ de = f2fs_find_target_dentry(&d, fname, NULL, prealloc, use_hash);
folio_unlock(ifolio);
if (IS_ERR(de)) {
*res_folio = ERR_CAST(de);
diff --git a/fs/libfs.c b/fs/libfs.c
index 9ea0ecc325a81..cab3d86483835 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1863,6 +1863,26 @@ static const struct dentry_operations generic_ci_dentry_ops = {
#endif
};
+#define DECRYPTED_NAME_PREALLOC_MIN_LEN 64
+static inline char *decrypted_name_prealloc_resize(
+ struct decrypted_name_prealloc *prealloc,
+ size_t wantlen)
+{
+ char *retbuf = NULL;
+
+ if (prealloc->name && wantlen >= prealloc->namelen)
+ return prealloc->name;
+
+ retbuf = kmalloc(wantlen + DECRYPTED_NAME_PREALLOC_MIN_LEN, GFP_KERNEL);
+ if (!retbuf)
+ return NULL;
+
+ kfree(prealloc->name);
+ prealloc->name = retbuf;
+ prealloc->namelen = wantlen + DECRYPTED_NAME_PREALLOC_MIN_LEN;
+ return retbuf;
+}
+
/**
* generic_ci_match() - Match a name (case-insensitively) with a dirent.
* This is a filesystem helper for comparison with directory entries.
@@ -1884,7 +1904,8 @@ static const struct dentry_operations generic_ci_dentry_ops = {
int generic_ci_match(const struct inode *parent,
const struct qstr *name,
const struct qstr *folded_name,
- const u8 *de_name, u32 de_name_len)
+ const u8 *de_name, u32 de_name_len,
+ struct decrypted_name_prealloc *prealloc)
{
const struct super_block *sb = parent->i_sb;
const struct unicode_map *um = sb->s_encoding;
@@ -1899,7 +1920,11 @@ int generic_ci_match(const struct inode *parent,
if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
return -EINVAL;
- decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
+ if (!prealloc)
+ decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
+ else
+ decrypted_name.name = decrypted_name_prealloc_resize(
+ prealloc, de_name_len);
if (!decrypted_name.name)
return -ENOMEM;
res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
@@ -1928,7 +1953,8 @@ int generic_ci_match(const struct inode *parent,
res = utf8_strncasecmp(um, name, &dirent);
out:
- kfree(decrypted_name.name);
+ if (!prealloc)
+ kfree(decrypted_name.name);
if (res < 0 && sb_has_strict_encoding(sb)) {
pr_err_ratelimited("Directory contains filename that is invalid UTF-8");
return 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4ec77da65f144..65307c8c11485 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3651,10 +3651,16 @@ extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
extern int generic_check_addressable(unsigned, u64);
extern void generic_set_sb_d_ops(struct super_block *sb);
+
+struct decrypted_name_prealloc {
+ char *name;
+ size_t namelen;
+};
extern int generic_ci_match(const struct inode *parent,
const struct qstr *name,
const struct qstr *folded_name,
- const u8 *de_name, u32 de_name_len);
+ const u8 *de_name, u32 de_name_len,
+ struct decrypted_name_prealloc *prealloc);
#if IS_ENABLED(CONFIG_UNICODE)
int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str);
--
2.34.1
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