fs/sysfs/inode.c

   1 /*
   2  * inode.c - basic inode and dentry operations.
   3  *
   4  * sysfs is Copyright (c) 2001-3 Patrick Mochel
   5  *
   6  * Please see Documentation/filesystems/sysfs.txt for more information.
   7  */
   8
   9 #undef DEBUG
  10
  11 #include <linux/pagemap.h>
  12 #include <linux/namei.h>
  13 #include <linux/backing-dev.h>
  14 #include <linux/capability.h>
  15 #include <linux/errno.h>
  16 #include <linux/sched.h>
  17 #include "sysfs.h"
  18
  19 extern struct super_block * sysfs_sb;
  20
  21 static const struct address_space_operations sysfs_aops = {
  22         .readpage       = simple_readpage,
  23         .prepare_write  = simple_prepare_write,
  24         .commit_write   = simple_commit_write
  25 };
  26
  27 static struct backing_dev_info sysfs_backing_dev_info = {
  28         .ra_pages       = 0,    /* No readahead */
  29         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  30 };
  31
  32 static const struct inode_operations sysfs_inode_operations ={
  33         .setattr        = sysfs_setattr,
  34 };
  35
  36 void sysfs_delete_inode(struct inode *inode)
  37 {
  38         /* Free the shadowed directory inode operations */
  39         if (sysfs_is_shadowed_inode(inode)) {
  40                 kfree(inode->i_op);
  41                 inode->i_op = NULL;
  42         }
  43         return generic_delete_inode(inode);
  44 }
  45
  46 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  47 {
  48         struct inode * inode = dentry->d_inode;
  49         struct sysfs_dirent * sd = dentry->d_fsdata;
  50         struct iattr * sd_iattr;
  51         unsigned int ia_valid = iattr->ia_valid;
  52         int error;
  53
  54         if (!sd)
  55                 return -EINVAL;
  56
  57         sd_iattr = sd->s_iattr;
  58
  59         error = inode_change_ok(inode, iattr);
  60         if (error)
  61                 return error;
  62
  63         error = inode_setattr(inode, iattr);
  64         if (error)
  65                 return error;
  66
  67         if (!sd_iattr) {
  68                 /* setting attributes for the first time, allocate now */
  69                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  70                 if (!sd_iattr)
  71                         return -ENOMEM;
  72                 /* assign default attributes */
  73                 sd_iattr->ia_mode = sd->s_mode;
  74                 sd_iattr->ia_uid = 0;
  75                 sd_iattr->ia_gid = 0;
  76                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  77                 sd->s_iattr = sd_iattr;
  78         }
  79
  80         /* attributes were changed atleast once in past */
  81
  82         if (ia_valid & ATTR_UID)
  83                 sd_iattr->ia_uid = iattr->ia_uid;
  84         if (ia_valid & ATTR_GID)
  85                 sd_iattr->ia_gid = iattr->ia_gid;
  86         if (ia_valid & ATTR_ATIME)
  87                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  88                                                 inode->i_sb->s_time_gran);
  89         if (ia_valid & ATTR_MTIME)
  90                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  91                                                 inode->i_sb->s_time_gran);
  92         if (ia_valid & ATTR_CTIME)
  93                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  94                                                 inode->i_sb->s_time_gran);
  95         if (ia_valid & ATTR_MODE) {
  96                 umode_t mode = iattr->ia_mode;
  97
  98                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  99                         mode &= ~S_ISGID;
 100                 sd_iattr->ia_mode = sd->s_mode = mode;
 101         }
 102
 103         return error;
 104 }
 105
 106 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 107 {
 108         inode->i_mode = mode;
 109         inode->i_uid = 0;
 110         inode->i_gid = 0;
 111         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 112 }
 113
 114 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 115 {
 116         inode->i_mode = iattr->ia_mode;
 117         inode->i_uid = iattr->ia_uid;
 118         inode->i_gid = iattr->ia_gid;
 119         inode->i_atime = iattr->ia_atime;
 120         inode->i_mtime = iattr->ia_mtime;
 121         inode->i_ctime = iattr->ia_ctime;
 122 }
 123
 124
 125 /*
 126  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 127  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 128  * held. At the same time, many of the VFS locking rules do not apply to
 129  * sysfs at all (cross directory rename for example). To untangle this mess
 130  * (which gives false positives in lockdep), we're giving sysfs inodes their
 131  * own class for i_mutex.
 132  */
 133 static struct lock_class_key sysfs_inode_imutex_key;
 134
 135 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 136 {
 137         inode->i_blocks = 0;
 138         inode->i_mapping->a_ops = &sysfs_aops;
 139         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 140         inode->i_op = &sysfs_inode_operations;
 141         inode->i_ino = sd->s_ino;
 142         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 143
 144         if (sd->s_iattr) {
 145                 /* sysfs_dirent has non-default attributes
 146                  * get them for the new inode from persistent copy
 147                  * in sysfs_dirent
 148                  */
 149                 set_inode_attr(inode, sd->s_iattr);
 150         } else
 151                 set_default_inode_attr(inode, sd->s_mode);
 152 }
 153
 154 /**
 155  *      sysfs_get_inode - get inode for sysfs_dirent
 156  *      @sd: sysfs_dirent to allocate inode for
 157  *
 158  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 159  *      is allocated and basics are initialized.  New inode is
 160  *      returned locked.
 161  *
 162  *      LOCKING:
 163  *      Kernel thread context (may sleep).
 164  *
 165  *      RETURNS:
 166  *      Pointer to allocated inode on success, NULL on failure.
 167  */
 168 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 169 {
 170         struct inode *inode;
 171
 172         inode = iget_locked(sysfs_sb, sd->s_ino);
 173         if (inode && (inode->i_state & I_NEW))
 174                 sysfs_init_inode(sd, inode);
 175
 176         return inode;
 177 }
 178
 179 /**
 180  *      sysfs_instantiate - instantiate dentry
 181  *      @dentry: dentry to be instantiated
 182  *      @inode: inode associated with @sd
 183  *
 184  *      Unlock @inode if locked and instantiate @dentry with @inode.
 185  *
 186  *      LOCKING:
 187  *      None.
 188  */
 189 void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
 190 {
 191         BUG_ON(!dentry || dentry->d_inode);
 192
 193         if (inode->i_state & I_NEW)
 194                 unlock_new_inode(inode);
 195
 196         d_instantiate(dentry, inode);
 197 }
 198
 199 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 200 {
 201         struct sysfs_addrm_cxt acxt;
 202         struct sysfs_dirent **pos, *sd;
 203
 204         if (!dir_sd)
 205                 return -ENOENT;
 206
 207         sysfs_addrm_start(&acxt, dir_sd);
 208
 209         for (pos = &dir_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
 210                 sd = *pos;
 211
 212                 if (!sysfs_type(sd))
 213                         continue;
 214                 if (!strcmp(sd->s_name, name)) {
 215                         *pos = sd->s_sibling;
 216                         sd->s_sibling = NULL;
 217                         sysfs_remove_one(&acxt, sd);
 218                         break;
 219                 }
 220         }
 221
 222         if (sysfs_addrm_finish(&acxt))
 223                 return 0;
 224         return -ENOENT;
 225 }