Re: [PATCH 4/8] vfs: Fold casefolding into vfs

Gabriel Krisman Bertazi
2019-12-03T19:31:23Z

Daniel Rosenberg <drosen@google.com> writes:

> Ext4 and F2fs are both using casefolding, and they, along with any other
> filesystem that adds the feature, will be using identical dentry_ops.
> Additionally, those dentry ops interfere with the dentry_ops required
> for fscrypt once we add support for casefolding and encryption.
> Moving this into the vfs removes code duplication as well as the
> complication with encryption.
>
> Currently this is pretty close to just moving the existing f2fs/ext4
> code up a level into the vfs, although there is a lot of room for
> improvement now.
>
> Signed-off-by: Daniel Rosenberg <drosen@google.com>
> ---
> fs/dcache.c | 35 +++++++++++++++++++++++++++++++++++
> fs/namei.c | 43 ++++++++++++++++++++++++++++++++++++++++---
> include/linux/fs.h | 12 ++++++++++++
> 3 files changed, 87 insertions(+), 3 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index f7931b682a0d..575f3c2c3f77 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -32,6 +32,7 @@
> #include <linux/bit_spinlock.h>
> #include <linux/rculist_bl.h>
> #include <linux/list_lru.h>
> +#include <linux/unicode.h>
> #include "internal.h"
> #include "mount.h"
>
> @@ -228,6 +229,13 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char
>
> #endif
>
> +bool needs_casefold(const struct inode *dir)
> +{
> + return IS_CASEFOLDED(dir) &&
> + (!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir));
> +}
> +EXPORT_SYMBOL(needs_casefold);
> +
> static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
> {
> /*
> @@ -247,7 +255,19 @@ static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
> * be no NUL in the ct/tcount data)
> */
> const unsigned char *cs = READ_ONCE(dentry->d_name.name);
> +#ifdef CONFIG_UNICODE
> + struct inode *parent = dentry->d_parent->d_inode;
>
> + if (unlikely(needs_casefold(parent))) {
> + const struct qstr n1 = QSTR_INIT(cs, tcount);
> + const struct qstr n2 = QSTR_INIT(ct, tcount);
> + int result = utf8_strncasecmp(dentry->d_sb->s_encoding,
> + &n1, &n2);
> +
> + if (result >= 0 || sb_has_enc_strict_mode(dentry->d_sb))
> + return result;
> + }
> +#endif
> return dentry_string_cmp(cs, ct, tcount);
> }
>
> @@ -2404,7 +2424,22 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
> * calculate the standard hash first, as the d_op->d_hash()
> * routine may choose to leave the hash value unchanged.
> */
> +#ifdef CONFIG_UNICODE
> + unsigned char *hname = NULL;
> + int hlen = name->len;
> +
> + if (IS_CASEFOLDED(dir->d_inode)) {
> + hname = kmalloc(PATH_MAX, GFP_ATOMIC);
> + if (!hname)
> + return ERR_PTR(-ENOMEM);
> + hlen = utf8_casefold(dir->d_sb->s_encoding,
> + name, hname, PATH_MAX);
> + }
> + name->hash = full_name_hash(dir, hname ?: name->name, hlen);
> + kfree(hname);
> +#else
> name->hash = full_name_hash(dir, name->name, name->len);
> +#endif
> if (dir->d_flags & DCACHE_OP_HASH) {
> int err = dir->d_op->d_hash(dir, name);
> if (unlikely(err < 0))
> diff --git a/fs/namei.c b/fs/namei.c
> index 2dda552bcf7a..b8d5cb0994ec 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -39,6 +39,7 @@
> #include <linux/bitops.h>
> #include <linux/init_task.h>
> #include <linux/uaccess.h>
> +#include <linux/unicode.h>
>
> #include "internal.h"
> #include "mount.h"
> @@ -2062,6 +2063,10 @@ static inline u64 hash_name(const void *salt, const char *name)
> static int link_path_walk(const char *name, struct nameidata *nd)
> {
> int err;
> +#ifdef CONFIG_UNICODE
> + char *hname = NULL;
> + int hlen = 0;
> +#endif
>
> if (IS_ERR(name))
> return PTR_ERR(name);
> @@ -2078,9 +2083,21 @@ static int link_path_walk(const char *name, struct nameidata *nd)
> err = may_lookup(nd);
> if (err)
> return err;
> -
> +#ifdef CONFIG_UNICODE
> + if (needs_casefold(nd->path.dentry->d_inode)) {
> + struct qstr str = QSTR_INIT(name, PATH_MAX);
> +
> + hname = kmalloc(PATH_MAX, GFP_ATOMIC);
> + if (!hname)
> + return -ENOMEM;
> + hlen = utf8_casefold(nd->path.dentry->d_sb->s_encoding,
> + &str, hname, PATH_MAX);
> + }
> + hash_len = hash_name(nd->path.dentry, hname ?: name);
> + kfree(hname);

It would be nice to reuse the memory allocation for the entire path walk
instead of allocating and freeing several times in a row. Still not
ideal, but I don't see how we could not have at least one allocation here.

> +#else
> hash_len = hash_name(nd->path.dentry, name);
> -
> +#endif
> type = LAST_NORM;
> if (name[0] == '.') switch (hashlen_len(hash_len)) {
> case 2:
> @@ -2452,9 +2469,29 @@ EXPORT_SYMBOL(vfs_path_lookup);
> static int lookup_one_len_common(const char *name, struct dentry *base,
> int len, struct qstr *this)
> {
> +#ifdef CONFIG_UNICODE
> + char *hname = NULL;
> + int hlen = len;
> +
> + if (needs_casefold(base->d_inode)) {
> + struct qstr str = QSTR_INIT(name, len);
> +
> + hname = kmalloc(PATH_MAX, GFP_ATOMIC);
> + if (!hname)
> + return -ENOMEM;
> + hlen = utf8_casefold(base->d_sb->s_encoding,
> + &str, hname, PATH_MAX);
> + }
> + this->hash = full_name_hash(base, hname ?: name, hlen);
> + kvfree(hname);
> +#else
> + this->hash = full_name_hash(base, name, len);
> +#endif
> this->name = name;
> this->len = len;
> - this->hash = full_name_hash(base, name, len);
> +#ifdef CONFIG_UNICODE
> + kfree(hname);
> +#endif
> if (!len)
> return -EACCES;
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c159a8bdee8b..38d1c20f3e6f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1382,6 +1382,12 @@ extern int send_sigurg(struct fown_struct *fown);
> #define SB_ACTIVE (1<<30)
> #define SB_NOUSER (1<<31)
>
> +/* These flags relate to encoding and casefolding */
> +#define SB_ENC_STRICT_MODE_FL (1 << 0)
> +
> +#define sb_has_enc_strict_mode(sb) \
> + (sb->s_encoding_flags & SB_ENC_STRICT_MODE_FL)
> +
> /*
> * Umount options
> */
> @@ -1449,6 +1455,10 @@ struct super_block {
> #endif
> #ifdef CONFIG_FS_VERITY
> const struct fsverity_operations *s_vop;
> +#endif
> +#ifdef CONFIG_UNICODE
> + struct unicode_map *s_encoding;
> + __u16 s_encoding_flags;
> #endif
> struct hlist_bl_head s_roots; /* alternate root dentries for NFS */
> struct list_head s_mounts; /* list of mounts; _not_ for fs use */
> @@ -2044,6 +2054,8 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
> #define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \
> (inode)->i_rdev == WHITEOUT_DEV)
>
> +extern bool needs_casefold(const struct inode *dir);
> +
> static inline bool HAS_UNMAPPED_ID(struct inode *inode)
> {
> return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);

--
Gabriel Krisman Bertazi