diff options
author | Al Viro <viro@zeniv.linux.org.uk> | 2011-03-16 09:07:58 -0400 |
---|---|---|
committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-03-16 16:48:06 -0400 |
commit | 1a102ff92579edeff5e3d5d3c76ca49977898f00 (patch) | |
tree | 5585d724c8a996b770bb7a621563a7535a8c0496 /Documentation/filesystems/vfs.txt | |
parent | 011949811b946bd3b72fca71200f197c6168a5f8 (diff) |
vfs: bury ->get_sb()
This is an ex-parrot.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
-rw-r--r-- | Documentation/filesystems/vfs.txt | 56 |
1 files changed, 32 insertions, 24 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 94cf97b901d7..ef0714aa8e40 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt | |||
@@ -95,10 +95,11 @@ functions: | |||
95 | extern int unregister_filesystem(struct file_system_type *); | 95 | extern int unregister_filesystem(struct file_system_type *); |
96 | 96 | ||
97 | The passed struct file_system_type describes your filesystem. When a | 97 | The passed struct file_system_type describes your filesystem. When a |
98 | request is made to mount a device onto a directory in your filespace, | 98 | request is made to mount a filesystem onto a directory in your namespace, |
99 | the VFS will call the appropriate get_sb() method for the specific | 99 | the VFS will call the appropriate mount() method for the specific |
100 | filesystem. The dentry for the mount point will then be updated to | 100 | filesystem. New vfsmount refering to the tree returned by ->mount() |
101 | point to the root inode for the new filesystem. | 101 | will be attached to the mountpoint, so that when pathname resolution |
102 | reaches the mountpoint it will jump into the root of that vfsmount. | ||
102 | 103 | ||
103 | You can see all filesystems that are registered to the kernel in the | 104 | You can see all filesystems that are registered to the kernel in the |
104 | file /proc/filesystems. | 105 | file /proc/filesystems. |
@@ -107,14 +108,14 @@ file /proc/filesystems. | |||
107 | struct file_system_type | 108 | struct file_system_type |
108 | ----------------------- | 109 | ----------------------- |
109 | 110 | ||
110 | This describes the filesystem. As of kernel 2.6.22, the following | 111 | This describes the filesystem. As of kernel 2.6.39, the following |
111 | members are defined: | 112 | members are defined: |
112 | 113 | ||
113 | struct file_system_type { | 114 | struct file_system_type { |
114 | const char *name; | 115 | const char *name; |
115 | int fs_flags; | 116 | int fs_flags; |
116 | int (*get_sb) (struct file_system_type *, int, | 117 | struct dentry (*mount) (struct file_system_type *, int, |
117 | const char *, void *, struct vfsmount *); | 118 | const char *, void *); |
118 | void (*kill_sb) (struct super_block *); | 119 | void (*kill_sb) (struct super_block *); |
119 | struct module *owner; | 120 | struct module *owner; |
120 | struct file_system_type * next; | 121 | struct file_system_type * next; |
@@ -128,11 +129,11 @@ struct file_system_type { | |||
128 | 129 | ||
129 | fs_flags: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.) | 130 | fs_flags: various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.) |
130 | 131 | ||
131 | get_sb: the method to call when a new instance of this | 132 | mount: the method to call when a new instance of this |
132 | filesystem should be mounted | 133 | filesystem should be mounted |
133 | 134 | ||
134 | kill_sb: the method to call when an instance of this filesystem | 135 | kill_sb: the method to call when an instance of this filesystem |
135 | should be unmounted | 136 | should be shut down |
136 | 137 | ||
137 | owner: for internal VFS use: you should initialize this to THIS_MODULE in | 138 | owner: for internal VFS use: you should initialize this to THIS_MODULE in |
138 | most cases. | 139 | most cases. |
@@ -141,7 +142,7 @@ struct file_system_type { | |||
141 | 142 | ||
142 | s_lock_key, s_umount_key: lockdep-specific | 143 | s_lock_key, s_umount_key: lockdep-specific |
143 | 144 | ||
144 | The get_sb() method has the following arguments: | 145 | The mount() method has the following arguments: |
145 | 146 | ||
146 | struct file_system_type *fs_type: describes the filesystem, partly initialized | 147 | struct file_system_type *fs_type: describes the filesystem, partly initialized |
147 | by the specific filesystem code | 148 | by the specific filesystem code |
@@ -153,32 +154,39 @@ The get_sb() method has the following arguments: | |||
153 | void *data: arbitrary mount options, usually comes as an ASCII | 154 | void *data: arbitrary mount options, usually comes as an ASCII |
154 | string (see "Mount Options" section) | 155 | string (see "Mount Options" section) |
155 | 156 | ||
156 | struct vfsmount *mnt: a vfs-internal representation of a mount point | 157 | The mount() method must return the root dentry of the tree requested by |
158 | caller. An active reference to its superblock must be grabbed and the | ||
159 | superblock must be locked. On failure it should return ERR_PTR(error). | ||
157 | 160 | ||
158 | The get_sb() method must determine if the block device specified | 161 | The arguments match those of mount(2) and their interpretation |
159 | in the dev_name and fs_type contains a filesystem of the type the method | 162 | depends on filesystem type. E.g. for block filesystems, dev_name is |
160 | supports. If it succeeds in opening the named block device, it initializes a | 163 | interpreted as block device name, that device is opened and if it |
161 | struct super_block descriptor for the filesystem contained by the block device. | 164 | contains a suitable filesystem image the method creates and initializes |
162 | On failure it returns an error. | 165 | struct super_block accordingly, returning its root dentry to caller. |
166 | |||
167 | ->mount() may choose to return a subtree of existing filesystem - it | ||
168 | doesn't have to create a new one. The main result from the caller's | ||
169 | point of view is a reference to dentry at the root of (sub)tree to | ||
170 | be attached; creation of new superblock is a common side effect. | ||
163 | 171 | ||
164 | The most interesting member of the superblock structure that the | 172 | The most interesting member of the superblock structure that the |
165 | get_sb() method fills in is the "s_op" field. This is a pointer to | 173 | mount() method fills in is the "s_op" field. This is a pointer to |
166 | a "struct super_operations" which describes the next level of the | 174 | a "struct super_operations" which describes the next level of the |
167 | filesystem implementation. | 175 | filesystem implementation. |
168 | 176 | ||
169 | Usually, a filesystem uses one of the generic get_sb() implementations | 177 | Usually, a filesystem uses one of the generic mount() implementations |
170 | and provides a fill_super() method instead. The generic methods are: | 178 | and provides a fill_super() callback instead. The generic variants are: |
171 | 179 | ||
172 | get_sb_bdev: mount a filesystem residing on a block device | 180 | mount_bdev: mount a filesystem residing on a block device |
173 | 181 | ||
174 | get_sb_nodev: mount a filesystem that is not backed by a device | 182 | mount_nodev: mount a filesystem that is not backed by a device |
175 | 183 | ||
176 | get_sb_single: mount a filesystem which shares the instance between | 184 | mount_single: mount a filesystem which shares the instance between |
177 | all mounts | 185 | all mounts |
178 | 186 | ||
179 | A fill_super() method implementation has the following arguments: | 187 | A fill_super() callback implementation has the following arguments: |
180 | 188 | ||
181 | struct super_block *sb: the superblock structure. The method fill_super() | 189 | struct super_block *sb: the superblock structure. The callback |
182 | must initialize this properly. | 190 | must initialize this properly. |
183 | 191 | ||
184 | void *data: arbitrary mount options, usually comes as an ASCII | 192 | void *data: arbitrary mount options, usually comes as an ASCII |