On 12/20, Daniel Lee wrote:
> 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 5c26d2f1d3f5
> ("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: 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219586
> Signed-off-by: Daniel Lee <chul...@google.com>
> ---
> v2:
> - Only update chash if use_hash is true
>  fs/f2fs/dir.c    | 40 +++++++++++++++++++++++++++++-----------
>  fs/f2fs/f2fs.h   |  6 ++++--
>  fs/f2fs/inline.c |  5 +++--
>  3 files changed, 36 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index 47a5c806cf16..3e8e5ddf9dbc 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -175,7 +175,8 @@ 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;
> @@ -183,7 +184,7 @@ static struct f2fs_dir_entry *find_in_block(struct inode 
> *dir,
>       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,
> @@ -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;
> @@ -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));
> @@ -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;
> @@ -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) {
> @@ -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;
> @@ -307,7 +313,10 @@ static struct f2fs_dir_entry *find_in_level(struct inode 
> *dir,
>               bidx++;
>       }
>  
> -     if (!de && room && F2FS_I(dir)->chash != fname->hash) {
> +     if (!use_hash && !de && ++bucket_no < nbucket)
> +             goto start_find_bucket;
> +
> +     if (use_hash && !de && room && F2FS_I(dir)->chash != fname->hash) {
>               F2FS_I(dir)->chash = fname->hash;
>               F2FS_I(dir)->clevel = level;
>       }
> @@ -323,11 +332,13 @@ 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;
>  
> +start_find_entry:

This label is only used by #if IS_ENABLED(CONFIG_UNICODE).

>       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;
>       }
>  
> @@ -343,11 +354,18 @@ 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;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index f523dd302bf6..1afebb9c4061 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -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,
> @@ -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,
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index cbd2a0d34804..3e3c35d4c98b 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -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;
> @@ -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);
> -- 
> 2.47.1.613.gc27f4b7a9f-goog


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