lunaix-os/kernel/fs/path_walk.c

   1 #include <lunaix/fs.h>
   2 #include <lunaix/mm/valloc.h>
   3 #include <lunaix/process.h>
   4 #include <lunaix/spike.h>
   5
   6 #include <klibc/string.h>
   7
   8 #define VFS_SYMLINK_DEPTH 16
   9
  10 extern struct lru_zone *dnode_lru, *inode_lru;
  11
  12 int
  13 __vfs_walk(struct v_dnode* start,
  14            const char* path,
  15            struct v_dnode** dentry,
  16            struct hstr* component,
  17            int walk_options,
  18            size_t depth,
  19            char* fname_buffer)
  20 {
  21     int errno = 0;
  22     int i = 0, j = 0;
  23
  24     if (depth >= VFS_SYMLINK_DEPTH) {
  25         return ELOOP;
  26     }
  27
  28     if (path[0] == VFS_PATH_DELIM || !start) {
  29         if ((walk_options & VFS_WALK_FSRELATIVE) && start) {
  30             start = start->super_block->root;
  31         } else {
  32             start = vfs_sysroot;
  33             if (!vfs_sysroot->mnt) {
  34                 panick("vfs: no root");
  35             }
  36         }
  37
  38         if (path[0] == VFS_PATH_DELIM) {
  39             i++;
  40         }
  41     }
  42
  43     assert(start);
  44
  45     struct v_dnode* dnode;
  46     struct v_inode* current_inode;
  47     struct v_dnode* current_level = start;
  48
  49     struct hstr name = HSTR(fname_buffer, 0);
  50
  51     char current = path[i++], lookahead;
  52     while (current) {
  53         lookahead = path[i++];
  54         if (current != VFS_PATH_DELIM) {
  55             if (j >= VFS_NAME_MAXLEN - 1) {
  56                 return ENAMETOOLONG;
  57             }
  58             if (!VFS_VALID_CHAR(current)) {
  59                 return EINVAL;
  60             }
  61             fname_buffer[j++] = current;
  62             if (lookahead) {
  63                 goto cont;
  64             }
  65         }
  66
  67         // handling cases like /^.*(\/+).*$/
  68         if (lookahead == VFS_PATH_DELIM) {
  69             goto cont;
  70         }
  71
  72         fname_buffer[j] = 0;
  73         name.len = j;
  74         hstr_rehash(&name, HSTR_FULL_HASH);
  75
  76         if (!lookahead && (walk_options & VFS_WALK_PARENT)) {
  77             if (component) {
  78                 hstrcpy(component, &name);
  79             }
  80             break;
  81         }
  82
  83         current_inode = current_level->inode;
  84
  85         if ((current_inode->itype & VFS_IFSYMLINK) &&
  86             !(walk_options & VFS_WALK_NOFOLLOW)) {
  87             const char* link;
  88
  89             lock_inode(current_inode);
  90             if ((errno =
  91                    current_inode->ops->read_symlink(current_inode, &link))) {
  92                 unlock_inode(current_inode);
  93                 goto error;
  94             }
  95             unlock_inode(current_inode);
  96
  97             errno = __vfs_walk(current_level->parent,
  98                                link,
  99                                &dnode,
 100                                NULL,
 101                                0,
 102                                depth + 1,
 103                                fname_buffer + name.len + 1);
 104
 105             if (errno) {
 106                 goto error;
 107             }
 108
 109             // reposition the resolved subtree pointed by symlink
 110             // vfs_dcache_rehash(current_level->parent, dnode);
 111             current_level = dnode;
 112             current_inode = dnode->inode;
 113         }
 114
 115         lock_dnode(current_level);
 116
 117         dnode = vfs_dcache_lookup(current_level, &name);
 118
 119         if (!dnode) {
 120             dnode = vfs_d_alloc(current_level, &name);
 121
 122             if (!dnode) {
 123                 errno = ENOMEM;
 124                 goto error;
 125             }
 126
 127             lock_inode(current_inode);
 128
 129             errno = current_inode->ops->dir_lookup(current_inode, dnode);
 130
 131             if (errno == ENOENT && (walk_options & VFS_WALK_MKPARENT)) {
 132                 if (!current_inode->ops->mkdir) {
 133                     errno = ENOTSUP;
 134                 } else {
 135                     errno = current_inode->ops->mkdir(current_inode, dnode);
 136                 }
 137             }
 138
 139             vfs_dcache_add(current_level, dnode);
 140             unlock_inode(current_inode);
 141
 142             if (errno) {
 143                 unlock_dnode(current_level);
 144                 goto cleanup;
 145             }
 146         }
 147
 148         unlock_dnode(current_level);
 149
 150         j = 0;
 151         current_level = dnode;
 152     cont:
 153         current = lookahead;
 154     };
 155
 156     *dentry = current_level;
 157     return 0;
 158
 159 cleanup:
 160     vfs_d_free(dnode);
 161 error:
 162     *dentry = NULL;
 163     return errno;
 164 }
 165
 166 int
 167 vfs_walk(struct v_dnode* start,
 168          const char* path,
 169          struct v_dnode** dentry,
 170          struct hstr* component,
 171          int options)
 172 {
 173     // allocate a file name stack for path walking and recursion to resolve
 174     // symlink
 175     char* name_buffer = valloc(2048);
 176
 177     int errno =
 178       __vfs_walk(start, path, dentry, component, options, 0, name_buffer);
 179
 180     vfree(name_buffer);
 181     return errno;
 182 }
 183
 184 int
 185 vfs_walk_proc(const char* path,
 186               struct v_dnode** dentry,
 187               struct hstr* component,
 188               int options)
 189 {
 190     return vfs_walk(__current->cwd, path, dentry, component, options);
 191 }