diff options
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 67 |
1 files changed, 50 insertions, 17 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 9d019d35728f..81e5be6e6e35 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -151,7 +151,7 @@ The get_sb() method has the following arguments: const char *dev_name: the device name we are mounting. void *data: arbitrary mount options, usually comes as an ASCII - string + string (see "Mount Options" section) struct vfsmount *mnt: a vfs-internal representation of a mount point @@ -182,7 +182,7 @@ A fill_super() method implementation has the following arguments: must initialize this properly. void *data: arbitrary mount options, usually comes as an ASCII - string + string (see "Mount Options" section) int silent: whether or not to be silent on error @@ -203,8 +203,6 @@ struct super_operations { struct inode *(*alloc_inode)(struct super_block *sb); void (*destroy_inode)(struct inode *); - void (*read_inode) (struct inode *); - void (*dirty_inode) (struct inode *); int (*write_inode) (struct inode *, int); void (*put_inode) (struct inode *); @@ -242,15 +240,6 @@ or bottom half). ->alloc_inode was defined and simply undoes anything done by ->alloc_inode. - read_inode: this method is called to read a specific inode from the - mounted filesystem. The i_ino member in the struct inode is - initialized by the VFS to indicate which inode to read. Other - members are filled in by this method. - - You can set this to NULL and use iget5_locked() instead of iget() - to read inodes. This is necessary for filesystems for which the - inode number is not sufficient to identify an inode. - dirty_inode: this method is called by the VFS to mark an inode dirty. write_inode: this method is called when the VFS needs to write an @@ -302,15 +291,16 @@ or bottom half). umount_begin: called when the VFS is unmounting a filesystem. - show_options: called by the VFS to show mount options for /proc/<pid>/mounts. + show_options: called by the VFS to show mount options for + /proc/<pid>/mounts. (see "Mount Options" section) quota_read: called by the VFS to read from filesystem quota file. quota_write: called by the VFS to write to filesystem quota file. -The read_inode() method is responsible for filling in the "i_op" -field. This is a pointer to a "struct inode_operations" which -describes the methods that can be performed on individual inodes. +Whoever sets up the inode is responsible for filling in the "i_op" field. This +is a pointer to a "struct inode_operations" which describes the methods that +can be performed on individual inodes. The Inode Object @@ -980,6 +970,49 @@ manipulate dentries: For further information on dentry locking, please refer to the document Documentation/filesystems/dentry-locking.txt. +Mount Options +============= + +Parsing options +--------------- + +On mount and remount the filesystem is passed a string containing a +comma separated list of mount options. The options can have either of +these forms: + + option + option=value + +The <linux/parser.h> header defines an API that helps parse these +options. There are plenty of examples on how to use it in existing +filesystems. + +Showing options +--------------- + +If a filesystem accepts mount options, it must define show_options() +to show all the currently active options. The rules are: + + - options MUST be shown which are not default or their values differ + from the default + + - options MAY be shown which are enabled by default or have their + default value + +Options used only internally between a mount helper and the kernel +(such as file descriptors), or which only have an effect during the +mounting (such as ones controlling the creation of a journal) are exempt +from the above rules. + +The underlying reason for the above rules is to make sure, that a +mount can be accurately replicated (e.g. umounting and mounting again) +based on the information found in /proc/mounts. + +A simple method of saving options at mount/remount time and showing +them is provided with the save_mount_options() and +generic_show_options() helper functions. Please note, that using +these may have drawbacks. For more info see header comments for these +functions in fs/namespace.c. Resources ========= |