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 int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
  37 {
  38         struct inode * inode = dentry->d_inode;
  39         struct sysfs_dirent * sd = dentry->d_fsdata;
  40         struct iattr * sd_iattr;
  41         unsigned int ia_valid = iattr->ia_valid;
  42         int error;
  43
  44         if (!sd)
  45                 return -EINVAL;
  46
  47         sd_iattr = sd->s_iattr;
  48
  49         error = inode_change_ok(inode, iattr);
  50         if (error)
  51                 return error;
  52
  53         error = inode_setattr(inode, iattr);
  54         if (error)
  55                 return error;
  56
  57         if (!sd_iattr) {
  58                 /* setting attributes for the first time, allocate now */
  59                 sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  60                 if (!sd_iattr)
  61                         return -ENOMEM;
  62                 /* assign default attributes */
  63                 sd_iattr->ia_mode = sd->s_mode;
  64                 sd_iattr->ia_uid = 0;
  65                 sd_iattr->ia_gid = 0;
  66                 sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  67                 sd->s_iattr = sd_iattr;
  68         }
  69
  70         /* attributes were changed atleast once in past */
  71
  72         if (ia_valid & ATTR_UID)
  73                 sd_iattr->ia_uid = iattr->ia_uid;
  74         if (ia_valid & ATTR_GID)
  75                 sd_iattr->ia_gid = iattr->ia_gid;
  76         if (ia_valid & ATTR_ATIME)
  77                 sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  78                                                 inode->i_sb->s_time_gran);
  79         if (ia_valid & ATTR_MTIME)
  80                 sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  81                                                 inode->i_sb->s_time_gran);
  82         if (ia_valid & ATTR_CTIME)
  83                 sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  84                                                 inode->i_sb->s_time_gran);
  85         if (ia_valid & ATTR_MODE) {
  86                 umode_t mode = iattr->ia_mode;
  87
  88                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  89                         mode &= ~S_ISGID;
  90                 sd_iattr->ia_mode = sd->s_mode = mode;
  91         }
  92
  93         return error;
  94 }
  95
  96 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
  97 {
  98         inode->i_mode = mode;
  99         inode->i_uid = 0;
 100         inode->i_gid = 0;
 101         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 102 }
 103
 104 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 105 {
 106         inode->i_mode = iattr->ia_mode;
 107         inode->i_uid = iattr->ia_uid;
 108         inode->i_gid = iattr->ia_gid;
 109         inode->i_atime = iattr->ia_atime;
 110         inode->i_mtime = iattr->ia_mtime;
 111         inode->i_ctime = iattr->ia_ctime;
 112 }
 113
 114
 115 /*
 116  * sysfs has a different i_mutex lock order behavior for i_mutex than other
 117  * filesystems; sysfs i_mutex is called in many places with subsystem locks
 118  * held. At the same time, many of the VFS locking rules do not apply to
 119  * sysfs at all (cross directory rename for example). To untangle this mess
 120  * (which gives false positives in lockdep), we're giving sysfs inodes their
 121  * own class for i_mutex.
 122  */
 123 static struct lock_class_key sysfs_inode_imutex_key;
 124
 125 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 126 {
 127         inode->i_blocks = 0;
 128         inode->i_mapping->a_ops = &sysfs_aops;
 129         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 130         inode->i_op = &sysfs_inode_operations;
 131         inode->i_ino = sd->s_ino;
 132         lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 133
 134         if (sd->s_iattr) {
 135                 /* sysfs_dirent has non-default attributes
 136                  * get them for the new inode from persistent copy
 137                  * in sysfs_dirent
 138                  */
 139                 set_inode_attr(inode, sd->s_iattr);
 140         } else
 141                 set_default_inode_attr(inode, sd->s_mode);
 142 }
 143
 144 /**
 145  *      sysfs_get_inode - get inode for sysfs_dirent
 146  *      @sd: sysfs_dirent to allocate inode for
 147  *
 148  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 149  *      is allocated and basics are initialized.  New inode is
 150  *      returned locked.
 151  *
 152  *      LOCKING:
 153  *      Kernel thread context (may sleep).
 154  *
 155  *      RETURNS:
 156  *      Pointer to allocated inode on success, NULL on failure.
 157  */
 158 struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 159 {
 160         struct inode *inode;
 161
 162         inode = iget_locked(sysfs_sb, sd->s_ino);
 163         if (inode && (inode->i_state & I_NEW))
 164                 sysfs_init_inode(sd, inode);
 165
 166         return inode;
 167 }
 168
 169 /**
 170  *      sysfs_instantiate - instantiate dentry
 171  *      @dentry: dentry to be instantiated
 172  *      @inode: inode associated with @sd
 173  *
 174  *      Unlock @inode if locked and instantiate @dentry with @inode.
 175  *
 176  *      LOCKING:
 177  *      None.
 178  */
 179 void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
 180 {
 181         BUG_ON(!dentry || dentry->d_inode);
 182
 183         if (inode->i_state & I_NEW)
 184                 unlock_new_inode(inode);
 185
 186         d_instantiate(dentry, inode);
 187 }
 188
 189 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
 190 {
 191         struct sysfs_addrm_cxt acxt;
 192         struct sysfs_dirent *sd;
 193
 194         if (!dir_sd)
 195                 return -ENOENT;
 196
 197         sysfs_addrm_start(&acxt, dir_sd);
 198
 199         sd = sysfs_find_dirent(dir_sd, name);
 200         if (sd)
 201                 sysfs_remove_one(&acxt, sd);
 202
 203         if (sysfs_addrm_finish(&acxt))
 204                 return 0;
 205         return -ENOENT;
 206 }