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From: Steve French <smfrench@gmail.com>
To: Paulo Alcantara <pc@cjr.nz>
Cc: CIFS <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH 5/7] cifs: fix path comparison and hash calc
Date: Sat, 5 Jun 2021 16:04:22 -0500	[thread overview]
Message-ID: <CAH2r5muf4Tthghai7dSsX4trQRDeCBb53t9H7sjuHqAnWHOCtw@mail.gmail.com> (raw)
In-Reply-To: <20210604222533.4760-6-pc@cjr.nz>

applied the other 6 patches to cifs-2.6.git for-next but this one
wouldn't apply to for-next so I left it out temporarily.

On Fri, Jun 4, 2021 at 5:26 PM Paulo Alcantara <pc@cjr.nz> wrote:
>
> Fix cache lookup and hash calculations when handling paths with
> different cases.
>
> Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
> ---
>  fs/cifs/dfs_cache.c | 168 ++++++++++++++++++++++++--------------------
>  1 file changed, 93 insertions(+), 75 deletions(-)
>
> diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> index c52fec3c4092..f7c4874ddc17 100644
> --- a/fs/cifs/dfs_cache.c
> +++ b/fs/cifs/dfs_cache.c
> @@ -424,12 +424,24 @@ int dfs_cache_init(void)
>         return rc;
>  }
>
> -static inline unsigned int cache_entry_hash(const void *data, int size)
> +static int cache_entry_hash(const void *data, int size, unsigned int *hash)
>  {
> -       unsigned int h;
> +       int i, clen;
> +       const unsigned char *s = data;
> +       wchar_t c;
> +       unsigned int h = 0;
>
> -       h = jhash(data, size, 0);
> -       return h & (CACHE_HTABLE_SIZE - 1);
> +       for (i = 0; i < size; i += clen) {
> +               clen = cache_cp->char2uni(&s[i], size - i, &c);
> +               if (unlikely(clen < 0)) {
> +                       cifs_dbg(VFS, "%s: can't convert char\n", __func__);
> +                       return clen;
> +               }
> +               c = cifs_toupper(c);
> +               h = jhash(&c, sizeof(c), h);
> +       }
> +       *hash = h % CACHE_HTABLE_SIZE;
> +       return 0;
>  }
>
>  /* Check whether second path component of @path is SYSVOL or NETLOGON */
> @@ -522,9 +534,7 @@ static int copy_ref_data(const struct dfs_info3_param *refs, int numrefs,
>  }
>
>  /* Allocate a new cache entry */
> -static struct cache_entry *alloc_cache_entry(const char *path,
> -                                            const struct dfs_info3_param *refs,
> -                                            int numrefs)
> +static struct cache_entry *alloc_cache_entry(struct dfs_info3_param *refs, int numrefs)
>  {
>         struct cache_entry *ce;
>         int rc;
> @@ -533,11 +543,9 @@ static struct cache_entry *alloc_cache_entry(const char *path,
>         if (!ce)
>                 return ERR_PTR(-ENOMEM);
>
> -       ce->path = kstrdup(path, GFP_KERNEL);
> -       if (!ce->path) {
> -               kmem_cache_free(cache_slab, ce);
> -               return ERR_PTR(-ENOMEM);
> -       }
> +       ce->path = refs[0].path_name;
> +       refs[0].path_name = NULL;
> +
>         INIT_HLIST_NODE(&ce->hlist);
>         INIT_LIST_HEAD(&ce->tlist);
>
> @@ -579,12 +587,18 @@ static void remove_oldest_entry_locked(void)
>  }
>
>  /* Add a new DFS cache entry */
> -static int add_cache_entry_locked(const char *path, unsigned int hash,
> -                                 struct dfs_info3_param *refs, int numrefs)
> +static int add_cache_entry_locked(struct dfs_info3_param *refs, int numrefs)
>  {
> +       int rc;
>         struct cache_entry *ce;
> +       unsigned int hash;
>
> -       ce = alloc_cache_entry(path, refs, numrefs);
> +       convert_delimiter(refs[0].path_name, '\\');
> +       rc = cache_entry_hash(refs[0].path_name, strlen(refs[0].path_name), &hash);
> +       if (rc)
> +               return rc;
> +
> +       ce = alloc_cache_entry(refs, numrefs);
>         if (IS_ERR(ce))
>                 return PTR_ERR(ce);
>
> @@ -604,57 +618,69 @@ static int add_cache_entry_locked(const char *path, unsigned int hash,
>         return 0;
>  }
>
> -static struct cache_entry *__lookup_cache_entry(const char *path)
> +/* Check if two DFS paths are equal.  @s1 and @s2 are expected to be in @cache_cp's charset */
> +static bool dfs_path_equal(const char *s1, int len1, const char *s2, int len2)
> +{
> +       int i, l1, l2;
> +       wchar_t c1, c2;
> +
> +       if (len1 != len2)
> +               return false;
> +
> +       for (i = 0; i < len1; i += l1) {
> +               l1 = cache_cp->char2uni(&s1[i], len1 - i, &c1);
> +               l2 = cache_cp->char2uni(&s2[i], len2 - i, &c2);
> +               if (unlikely(l1 < 0 && l2 < 0)) {
> +                       if (s1[i] != s2[i])
> +                               return false;
> +                       l1 = 1;
> +                       continue;
> +               }
> +               if (l1 != l2)
> +                       return false;
> +               if (cifs_toupper(c1) != cifs_toupper(c2))
> +                       return false;
> +       }
> +       return true;
> +}
> +
> +static struct cache_entry *__lookup_cache_entry(const char *path, unsigned int hash, int len)
>  {
>         struct cache_entry *ce;
> -       unsigned int h;
> -       bool found = false;
>
> -       h = cache_entry_hash(path, strlen(path));
> -
> -       hlist_for_each_entry(ce, &cache_htable[h], hlist) {
> -               if (!strcasecmp(path, ce->path)) {
> -                       found = true;
> +       hlist_for_each_entry(ce, &cache_htable[hash], hlist) {
> +               if (dfs_path_equal(ce->path, strlen(ce->path), path, len)) {
>                         dump_ce(ce);
> -                       break;
> +                       return ce;
>                 }
>         }
> -
> -       if (!found)
> -               ce = ERR_PTR(-ENOENT);
> -       return ce;
> +       return ERR_PTR(-EEXIST);
>  }
>
>  /*
> - * Find a DFS cache entry in hash table and optionally check prefix path against
> - * @path.
> - * Use whole path components in the match.
> - * Must be called with htable_rw_lock held.
> + * Find a DFS cache entry in hash table and optionally check prefix path against normalized @path.
>   *
> - * Return ERR_PTR(-ENOENT) if the entry is not found.
> + * Use whole path components in the match.  Must be called with htable_rw_lock held.
> + *
> + * Return ERR_PTR(-EEXIST) if the entry is not found.
>   */
> -static struct cache_entry *lookup_cache_entry(const char *path, unsigned int *hash)
> +static struct cache_entry *lookup_cache_entry(const char *path)
>  {
> -       struct cache_entry *ce = ERR_PTR(-ENOENT);
> -       unsigned int h;
> +       struct cache_entry *ce;
>         int cnt = 0;
> -       char *npath;
> -       char *s, *e;
> -       char sep;
> +       const char *s = path, *e;
> +       char sep = *s;
> +       unsigned int hash;
> +       int rc;
>
> -       npath = kstrdup(path, GFP_KERNEL);
> -       if (!npath)
> -               return ERR_PTR(-ENOMEM);
> -
> -       s = npath;
> -       sep = *npath;
>         while ((s = strchr(s, sep)) && ++cnt < 3)
>                 s++;
>
>         if (cnt < 3) {
> -               h = cache_entry_hash(path, strlen(path));
> -               ce = __lookup_cache_entry(path);
> -               goto out;
> +               rc = cache_entry_hash(path, strlen(path), &hash);
> +               if (rc)
> +                       return ERR_PTR(rc);
> +               return __lookup_cache_entry(path, hash, strlen(path));
>         }
>         /*
>          * Handle paths that have more than two path components and are a complete prefix of the DFS
> @@ -662,36 +688,29 @@ static struct cache_entry *lookup_cache_entry(const char *path, unsigned int *ha
>          *
>          * See MS-DFSC 3.2.5.5 "Receiving a Root Referral Request or Link Referral Request".
>          */
> -       h = cache_entry_hash(npath, strlen(npath));
> -       e = npath + strlen(npath) - 1;
> +       e = path + strlen(path) - 1;
>         while (e > s) {
> -               char tmp;
> +               int len;
>
>                 /* skip separators */
>                 while (e > s && *e == sep)
>                         e--;
>                 if (e == s)
> -                       goto out;
> -
> -               tmp = *(e+1);
> -               *(e+1) = 0;
> -
> -               ce = __lookup_cache_entry(npath);
> -               if (!IS_ERR(ce)) {
> -                       h = cache_entry_hash(npath, strlen(npath));
>                         break;
> -               }
>
> -               *(e+1) = tmp;
> +               len = e + 1 - path;
> +               rc = cache_entry_hash(path, len, &hash);
> +               if (rc)
> +                       return ERR_PTR(rc);
> +               ce = __lookup_cache_entry(path, hash, len);
> +               if (!IS_ERR(ce))
> +                       return ce;
> +
>                 /* backward until separator */
>                 while (e > s && *e != sep)
>                         e--;
>         }
> -out:
> -       if (hash)
> -               *hash = h;
> -       kfree(npath);
> -       return ce;
> +       return ERR_PTR(-EEXIST);
>  }
>
>  /**
> @@ -717,7 +736,7 @@ static int update_cache_entry_locked(const char *path, const struct dfs_info3_pa
>         struct cache_entry *ce;
>         char *s, *th = NULL;
>
> -       ce = lookup_cache_entry(path, NULL);
> +       ce = lookup_cache_entry(path);
>         if (IS_ERR(ce))
>                 return PTR_ERR(ce);
>
> @@ -767,7 +786,6 @@ static int get_dfs_referral(const unsigned int xid, struct cifs_ses *ses, const
>  static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, const char *path)
>  {
>         int rc;
> -       unsigned int hash;
>         struct cache_entry *ce;
>         struct dfs_info3_param *refs = NULL;
>         int numrefs = 0;
> @@ -777,7 +795,7 @@ static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, cons
>
>         down_write(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(path, &hash);
> +       ce = lookup_cache_entry(path);
>         if (!IS_ERR(ce)) {
>                 if (!cache_entry_expired(ce)) {
>                         dump_ce(ce);
> @@ -808,7 +826,7 @@ static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, cons
>                 remove_oldest_entry_locked();
>         }
>
> -       rc = add_cache_entry_locked(path, hash, refs, numrefs);
> +       rc = add_cache_entry_locked(refs, numrefs);
>         if (!rc)
>                 atomic_inc(&cache_count);
>
> @@ -940,7 +958,7 @@ int dfs_cache_find(const unsigned int xid, struct cifs_ses *ses, const struct nl
>
>         down_read(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(npath, NULL);
> +       ce = lookup_cache_entry(npath);
>         if (IS_ERR(ce)) {
>                 up_read(&htable_rw_lock);
>                 rc = PTR_ERR(ce);
> @@ -987,7 +1005,7 @@ int dfs_cache_noreq_find(const char *path, struct dfs_info3_param *ref,
>
>         down_read(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(path, NULL);
> +       ce = lookup_cache_entry(path);
>         if (IS_ERR(ce)) {
>                 rc = PTR_ERR(ce);
>                 goto out_unlock;
> @@ -1044,7 +1062,7 @@ int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses,
>
>         down_write(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(npath, NULL);
> +       ce = lookup_cache_entry(npath);
>         if (IS_ERR(ce)) {
>                 rc = PTR_ERR(ce);
>                 goto out_unlock;
> @@ -1098,7 +1116,7 @@ int dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt_
>
>         down_write(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(path, NULL);
> +       ce = lookup_cache_entry(path);
>         if (IS_ERR(ce)) {
>                 rc = PTR_ERR(ce);
>                 goto out_unlock;
> @@ -1147,7 +1165,7 @@ int dfs_cache_get_tgt_referral(const char *path, const struct dfs_cache_tgt_iter
>
>         down_read(&htable_rw_lock);
>
> -       ce = lookup_cache_entry(path, NULL);
> +       ce = lookup_cache_entry(path);
>         if (IS_ERR(ce)) {
>                 rc = PTR_ERR(ce);
>                 goto out_unlock;
> --
> 2.31.1
>


-- 
Thanks,

Steve

  reply	other threads:[~2021-06-05 21:05 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-04 22:25 [PATCH 0/7] dfs fixes Paulo Alcantara
2021-06-04 22:25 ` [PATCH 1/7] cifs: do not send tree disconnect to ipc shares Paulo Alcantara
2021-06-04 22:25 ` [PATCH 2/7] cifs: get rid of @noreq param in __dfs_cache_find() Paulo Alcantara
2021-06-04 22:25 ` [PATCH 3/7] cifs: keep referral server sessions alive Paulo Alcantara
2021-06-04 22:25 ` [PATCH 4/7] cifs: handle different charsets in dfs cache Paulo Alcantara
2021-06-04 22:25 ` [PATCH 5/7] cifs: fix path comparison and hash calc Paulo Alcantara
2021-06-05 21:04   ` Steve French [this message]
2021-06-04 22:25 ` [PATCH 6/7] cifs: set a minimum of 2 minutes for refreshing dfs cache Paulo Alcantara
2021-06-04 22:25 ` [PATCH 7/7] cifs: do not share tcp servers with dfs mounts Paulo Alcantara
2021-06-05 21:05 ` [PATCH 0/7] dfs fixes Steve French

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