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_dnode* current_level = start;
  47     struct v_inode* current_inode = current_level->inode;
  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         lock_dnode(current_level);
  84
  85         dnode = vfs_dcache_lookup(current_level, &name);
  86
  87         if (!dnode) {
  88             dnode = vfs_d_alloc(current_level, &name);
  89
  90             if (!dnode) {
  91                 errno = ENOMEM;
  92                 goto error;
  93             }
  94
  95             lock_inode(current_inode);
  96
  97             errno = current_inode->ops->dir_lookup(current_inode, dnode);
  98
  99             if (errno == ENOENT && (walk_options & VFS_WALK_MKPARENT)) {
 100                 if (!current_inode->ops->mkdir) {
 101                     errno = ENOTSUP;
 102                 } else {
 103                     errno = current_inode->ops->mkdir(current_inode, dnode);
 104                 }
 105             }
 106
 107             vfs_dcache_add(current_level, dnode);
 108             unlock_inode(current_inode);
 109
 110             if (errno) {
 111                 unlock_dnode(current_level);
 112                 goto cleanup;
 113             }
 114         }
 115
 116         unlock_dnode(current_level);
 117
 118         j = 0;
 119         current_level = dnode;
 120         current_inode = current_level->inode;
 121
 122         if ((current_inode->itype & F_MSLNK) &&
 123             !(walk_options & VFS_WALK_NOFOLLOW)) {
 124             const char* link;
 125
 126             if (!current_inode->ops->read_symlink) {
 127                 errno = ENOTSUP;
 128                 goto error;
 129             }
 130
 131             lock_inode(current_inode);
 132             if ((errno =
 133                    current_inode->ops->read_symlink(current_inode, &link))) {
 134                 unlock_inode(current_inode);
 135                 goto error;
 136             }
 137             unlock_inode(current_inode);
 138
 139             errno = __vfs_walk(current_level->parent,
 140                                link,
 141                                &dnode,
 142                                NULL,
 143                                0,
 144                                depth + 1,
 145                                fname_buffer + name.len + 1);
 146
 147             if (errno) {
 148                 goto error;
 149             }
 150
 151             current_level = dnode;
 152             current_inode = dnode->inode;
 153         }
 154
 155     cont:
 156         current = lookahead;
 157     };
 158
 159     *dentry = current_level;
 160     return 0;
 161
 162 cleanup:
 163     vfs_d_free(dnode);
 164 error:
 165     *dentry = NULL;
 166     return errno;
 167 }
 168
 169 int
 170 vfs_walk(struct v_dnode* start,
 171          const char* path,
 172          struct v_dnode** dentry,
 173          struct hstr* component,
 174          int options)
 175 {
 176     if (!path) {
 177         *dentry = NULL;
 178         return 0;
 179     }
 180
 181     // allocate a file name stack for path walking and recursion to resolve
 182     // symlink
 183     char* name_buffer = valloc(2048);
 184
 185     int errno =
 186       __vfs_walk(start, path, dentry, component, options, 0, name_buffer);
 187
 188     vfree(name_buffer);
 189     return errno;
 190 }
 191
 192 int
 193 vfs_walk_proc(const char* path,
 194               struct v_dnode** dentry,
 195               struct hstr* component,
 196               int options)
 197 {
 198     return vfs_walk(__current->cwd, path, dentry, component, options);
 199 }