> On Jul 16, 2021, at 12:36 AM, Chung-Chiang Cheng <cccheng@xxxxxxxxxxxx> wrote:
>
> hfsplus uses the case-insensitive filenames by default, but VFS negative
> dentries are incompatible with case-insensitive. For example, the
> following instructions will get a cached filename 'aaa' which isn't
> expected. There is no such problem in macOS.
>
> touch aaa
> rm aaa
> touch AAA
>
> This patch takes the same approach to drop negative dentires as vfat does.
> The dentry is revalidated without blocking and storing to the dentry,
> and should be safe in rcu-walk.
>
> Signed-off-by: Chung-Chiang Cheng <cccheng@xxxxxxxxxxxx>
> ---
> fs/hfsplus/hfsplus_fs.h | 1 +
> fs/hfsplus/inode.c | 1 +
> fs/hfsplus/unicode.c | 32 ++++++++++++++++++++++++++++++++
> 3 files changed, 34 insertions(+)
>
> diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
> index 1798949f269b..4ae7f1ca1584 100644
> --- a/fs/hfsplus/hfsplus_fs.h
> +++ b/fs/hfsplus/hfsplus_fs.h
> @@ -520,6 +520,7 @@ int hfsplus_asc2uni(struct super_block *sb, struct hfsplus_unistr *ustr,
> int hfsplus_hash_dentry(const struct dentry *dentry, struct qstr *str);
> int hfsplus_compare_dentry(const struct dentry *dentry, unsigned int len,
> const char *str, const struct qstr *name);
> +int hfsplus_revalidate_dentry(struct dentry *dentry, unsigned int flags);
>
> /* wrapper.c */
> int hfsplus_submit_bio(struct super_block *sb, sector_t sector, void *buf,
> diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
> index 6fef67c2a9f0..4188a0760118 100644
> --- a/fs/hfsplus/inode.c
> +++ b/fs/hfsplus/inode.c
> @@ -179,6 +179,7 @@ const struct address_space_operations hfsplus_aops = {
> const struct dentry_operations hfsplus_dentry_operations = {
> .d_hash = hfsplus_hash_dentry,
> .d_compare = hfsplus_compare_dentry,
> + .d_revalidate = hfsplus_revalidate_dentry,
> };
>
> static void hfsplus_get_perms(struct inode *inode,
> diff --git a/fs/hfsplus/unicode.c b/fs/hfsplus/unicode.c
> index 73342c925a4b..e336631334eb 100644
> --- a/fs/hfsplus/unicode.c
> +++ b/fs/hfsplus/unicode.c
> @@ -10,6 +10,7 @@
> */
>
> #include <linux/types.h>
> +#include <linux/namei.h>
> #include <linux/nls.h>
> #include "hfsplus_fs.h"
> #include "hfsplus_raw.h"
> @@ -518,3 +519,34 @@ int hfsplus_compare_dentry(const struct dentry *dentry,
> return 1;
> return 0;
> }
> +
> +int hfsplus_revalidate_dentry(struct dentry *dentry, unsigned int flags)
> +{
What’s about this code?
If (flags & LOOKUP_RCU)
return -ECHILD;
Do we really need to miss it here?
Thanks,
Slava.
> + /*
> + * dentries are always valid when disabling casefold.
> + */
> + if (!test_bit(HFSPLUS_SB_CASEFOLD, &HFSPLUS_SB(dentry->d_sb)->flags))
> + return 1;
> +
> + /*
> + * Positive dentries are valid when enabling casefold.
> + *
> + * Note, rename() to existing directory entry will have ->d_inode, and
> + * will use existing name which isn't specified name by user.
> + *
> + * We may be able to drop this positive dentry here. But dropping
> + * positive dentry isn't good idea. So it's unsupported like
> + * rename("filename", "FILENAME") for now.
> + */
> + if (d_really_is_positive(dentry))
> + return 1;
> +
> + /*
> + * Drop the negative dentry, in order to make sure to use the case
> + * sensitive name which is specified by user if this is for creation.
> + */
> + if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
> + return 0;
> +
> + return 1;
> +}
> --
> 2.25.1
>
