Skip to content

Commit

Permalink
f2fs: Introduce linear search for dentries
Browse files Browse the repository at this point in the history 
This patch addresses an issue where some files in case-insensitive
directories become inaccessible due to changes in how the kernel function,
utf8_casefold(), generates case-folded strings from the commit 5c26d2f
("unicode: Don't special case ignorable code points").

F2FS uses these case-folded names to calculate hash values for locating
dentries and stores them on disk. Since utf8_casefold() can produce
different output across kernel versions, stored hash values and newly
calculated hash values may differ. This results in affected files no
longer being found via the hash-based lookup.

To resolve this, the patch introduces a linear search fallback.
If the initial hash-based search fails, F2FS will sequentially scan the
directory entries.

Fixes: 5c26d2f ("unicode: Don't special case ignorable code points")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219586
Signed-off-by: Daniel Lee <chullee@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
  • Loading branch information
Daniel Lee authored and Jaegeuk Kim committed Jan 8, 2025
1 parent d217b5c commit 91b587b
Show file tree
Hide file tree
Showing 3 changed files with 45 additions and 19 deletions.
53 changes: 38 additions & 15 deletions fs/f2fs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -175,15 +175,16 @@ static unsigned long dir_block_index(unsigned int level,
static struct f2fs_dir_entry *find_in_block(struct inode *dir,
struct page *dentry_page,
const struct f2fs_filename *fname,
int *max_slots)
int *max_slots,
bool use_hash)
{
struct f2fs_dentry_block *dentry_blk;
struct f2fs_dentry_ptr d;

dentry_blk = (struct f2fs_dentry_block *)page_address(dentry_page);

make_dentry_ptr_block(dir, &d, dentry_blk);
return f2fs_find_target_dentry(&d, fname, max_slots);
return f2fs_find_target_dentry(&d, fname, max_slots, use_hash);
}

static inline int f2fs_match_name(const struct inode *dir,
Expand All @@ -208,7 +209,8 @@ 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)
const struct f2fs_filename *fname, int *max_slots,
bool use_hash)
{
struct f2fs_dir_entry *de;
unsigned long bit_pos = 0;
Expand All @@ -231,7 +233,7 @@ struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
continue;
}

if (de->hash_code == fname->hash) {
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));
Expand All @@ -258,11 +260,12 @@ struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
static struct f2fs_dir_entry *find_in_level(struct inode *dir,
unsigned int level,
const struct f2fs_filename *fname,
struct page **res_page)
struct page **res_page,
bool use_hash)
{
int s = GET_DENTRY_SLOTS(fname->disk_name.len);
unsigned int nbucket, nblock;
unsigned int bidx, end_block;
unsigned int bidx, end_block, bucket_no;
struct page *dentry_page;
struct f2fs_dir_entry *de = NULL;
pgoff_t next_pgofs;
Expand All @@ -272,8 +275,11 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
nblock = bucket_blocks(level);

bucket_no = use_hash ? le32_to_cpu(fname->hash) % nbucket : 0;

start_find_bucket:
bidx = dir_block_index(level, F2FS_I(dir)->i_dir_level,
le32_to_cpu(fname->hash) % nbucket);
bucket_no);
end_block = bidx + nblock;

while (bidx < end_block) {
Expand All @@ -290,7 +296,7 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
}
}

de = find_in_block(dir, dentry_page, fname, &max_slots);
de = find_in_block(dir, dentry_page, fname, &max_slots, use_hash);
if (IS_ERR(de)) {
*res_page = ERR_CAST(de);
de = NULL;
Expand All @@ -307,12 +313,18 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
bidx++;
}

if (!de && room && F2FS_I(dir)->chash != fname->hash) {
F2FS_I(dir)->chash = fname->hash;
F2FS_I(dir)->clevel = level;
}
if (de)
return de;

return de;
if (likely(use_hash)) {
if (room && F2FS_I(dir)->chash != fname->hash) {
F2FS_I(dir)->chash = fname->hash;
F2FS_I(dir)->clevel = level;
}
} else if (++bucket_no < nbucket) {
goto start_find_bucket;
}
return NULL;
}

struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
Expand All @@ -323,11 +335,15 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
struct f2fs_dir_entry *de = NULL;
unsigned int max_depth;
unsigned int level;
bool use_hash = true;

*res_page = NULL;

#if IS_ENABLED(CONFIG_UNICODE)
start_find_entry:
#endif
if (f2fs_has_inline_dentry(dir)) {
de = f2fs_find_in_inline_dir(dir, fname, res_page);
de = f2fs_find_in_inline_dir(dir, fname, res_page, use_hash);
goto out;
}

Expand All @@ -343,11 +359,18 @@ 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_page);
de = find_in_level(dir, level, fname, res_page, use_hash);
if (de || IS_ERR(*res_page))
break;
}

out:
#if IS_ENABLED(CONFIG_UNICODE)
if (IS_CASEFOLDED(dir) && !de && use_hash) {
use_hash = false;
goto start_find_entry;
}
#endif
/* This is to increase the speed of f2fs_create */
if (!de)
F2FS_I(dir)->task = current;
Expand Down
6 changes: 4 additions & 2 deletions fs/f2fs/f2fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3588,7 +3588,8 @@ int f2fs_prepare_lookup(struct inode *dir, struct dentry *dentry,
struct f2fs_filename *fname);
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);
const struct f2fs_filename *fname, int *max_slots,
bool use_hash);
int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
unsigned int start_pos, struct fscrypt_str *fstr);
void f2fs_do_make_empty_dir(struct inode *inode, struct inode *parent,
Expand Down Expand Up @@ -4224,7 +4225,8 @@ int f2fs_write_inline_data(struct inode *inode, struct folio *folio);
int f2fs_recover_inline_data(struct inode *inode, struct page *npage);
struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
const struct f2fs_filename *fname,
struct page **res_page);
struct page **res_page,
bool use_hash);
int f2fs_make_empty_inline_dir(struct inode *inode, struct inode *parent,
struct page *ipage);
int f2fs_add_inline_entry(struct inode *dir, const struct f2fs_filename *fname,
Expand Down
5 changes: 3 additions & 2 deletions fs/f2fs/inline.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -352,7 +352,8 @@ int f2fs_recover_inline_data(struct inode *inode, struct page *npage)

struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
const struct f2fs_filename *fname,
struct page **res_page)
struct page **res_page,
bool use_hash)
{
struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
struct f2fs_dir_entry *de;
Expand All @@ -369,7 +370,7 @@ struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
inline_dentry = inline_data_addr(dir, ipage);

make_dentry_ptr_inline(dir, &d, inline_dentry);
de = f2fs_find_target_dentry(&d, fname, NULL);
de = f2fs_find_target_dentry(&d, fname, NULL, use_hash);
unlock_page(ipage);
if (IS_ERR(de)) {
*res_page = ERR_CAST(de);
Expand Down

0 comments on commit 91b587b

Please sign in to comment.