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Diffstat (limited to 'Documentation/filesystems/vfs.rst')
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 107 |
1 files changed, 87 insertions, 20 deletions
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index c53f30251a66..769be5230210 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -107,7 +107,7 @@ file /proc/filesystems. struct file_system_type ----------------------- -This describes the filesystem. As of kernel 2.6.39, the following +This describes the filesystem. The following members are defined: .. code-block:: c @@ -115,14 +115,24 @@ members are defined: struct file_system_type { const char *name; int fs_flags; + int (*init_fs_context)(struct fs_context *); + const struct fs_parameter_spec *parameters; struct dentry *(*mount) (struct file_system_type *, int, - const char *, void *); + const char *, void *); void (*kill_sb) (struct super_block *); struct module *owner; struct file_system_type * next; - struct list_head fs_supers; + struct hlist_head fs_supers; + struct lock_class_key s_lock_key; struct lock_class_key s_umount_key; + struct lock_class_key s_vfs_rename_key; + struct lock_class_key s_writers_key[SB_FREEZE_LEVELS]; + + struct lock_class_key i_lock_key; + struct lock_class_key i_mutex_key; + struct lock_class_key invalidate_lock_key; + struct lock_class_key i_mutex_dir_key; }; ``name`` @@ -132,6 +142,15 @@ members are defined: ``fs_flags`` various flags (i.e. FS_REQUIRES_DEV, FS_NO_DCACHE, etc.) +``init_fs_context`` + Initializes 'struct fs_context' ->ops and ->fs_private fields with + filesystem-specific data. + +``parameters`` + Pointer to the array of filesystem parameters descriptors + 'struct fs_parameter_spec'. + More info in Documentation/filesystems/mount_api.rst. + ``mount`` the method to call when a new instance of this filesystem should be mounted @@ -148,7 +167,11 @@ members are defined: ``next`` for internal VFS use: you should initialize this to NULL - s_lock_key, s_umount_key: lockdep-specific +``fs_supers`` + for internal VFS use: hlist of filesystem instances (superblocks) + + s_lock_key, s_umount_key, s_vfs_rename_key, s_writers_key, + i_lock_key, i_mutex_key, invalidate_lock_key, i_mutex_dir_key: lockdep-specific The mount() method has the following arguments: @@ -222,33 +245,42 @@ struct super_operations ----------------------- This describes how the VFS can manipulate the superblock of your -filesystem. As of kernel 2.6.22, the following members are defined: +filesystem. The following members are defined: .. code-block:: c struct super_operations { struct inode *(*alloc_inode)(struct super_block *sb); void (*destroy_inode)(struct inode *); + void (*free_inode)(struct inode *); void (*dirty_inode) (struct inode *, int flags); - int (*write_inode) (struct inode *, int); - void (*drop_inode) (struct inode *); - void (*delete_inode) (struct inode *); + int (*write_inode) (struct inode *, struct writeback_control *wbc); + int (*drop_inode) (struct inode *); + void (*evict_inode) (struct inode *); void (*put_super) (struct super_block *); int (*sync_fs)(struct super_block *sb, int wait); + int (*freeze_super) (struct super_block *); int (*freeze_fs) (struct super_block *); + int (*thaw_super) (struct super_block *); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); int (*remount_fs) (struct super_block *, int *, char *); - void (*clear_inode) (struct inode *); void (*umount_begin) (struct super_block *); int (*show_options)(struct seq_file *, struct dentry *); + int (*show_devname)(struct seq_file *, struct dentry *); + int (*show_path)(struct seq_file *, struct dentry *); + int (*show_stats)(struct seq_file *, struct dentry *); ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t); ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t); - int (*nr_cached_objects)(struct super_block *); - void (*free_cached_objects)(struct super_block *, int); + struct dquot **(*get_dquots)(struct inode *); + + long (*nr_cached_objects)(struct super_block *, + struct shrink_control *); + long (*free_cached_objects)(struct super_block *, + struct shrink_control *); }; All methods are called without any locks being held, unless otherwise @@ -269,6 +301,11 @@ or bottom half). ->alloc_inode was defined and simply undoes anything done by ->alloc_inode. +``free_inode`` + this method is called from RCU callback. If you use call_rcu() + in ->destroy_inode to free 'struct inode' memory, then it's + better to release memory in this method. + ``dirty_inode`` this method is called by the VFS when an inode is marked dirty. This is specifically for the inode itself being marked dirty, @@ -296,8 +333,12 @@ or bottom half). practice of using "force_delete" in the put_inode() case, but does not have the races that the "force_delete()" approach had. -``delete_inode`` - called when the VFS wants to delete an inode +``evict_inode`` + called when the VFS wants to evict an inode. Caller does + *not* evict the pagecache or inode-associated metadata buffers; + the method has to use truncate_inode_pages_final() to get rid + of those. Caller makes sure async writeback cannot be running for + the inode while (or after) ->evict_inode() is called. Optional. ``put_super`` called when the VFS wishes to free the superblock @@ -308,14 +349,25 @@ or bottom half). superblock. The second parameter indicates whether the method should wait until the write out has been completed. Optional. +``freeze_super`` + Called instead of ->freeze_fs callback if provided. + Main difference is that ->freeze_super is called without taking + down_write(&sb->s_umount). If filesystem implements it and wants + ->freeze_fs to be called too, then it has to call ->freeze_fs + explicitly from this callback. Optional. + ``freeze_fs`` called when VFS is locking a filesystem and forcing it into a consistent state. This method is currently used by the Logical - Volume Manager (LVM). + Volume Manager (LVM) and ioctl(FIFREEZE). Optional. + +``thaw_super`` + called when VFS is unlocking a filesystem and making it writable + again after ->freeze_super. Optional. ``unfreeze_fs`` called when VFS is unlocking a filesystem and making it writable - again. + again after ->freeze_fs. Optional. ``statfs`` called when the VFS needs to get filesystem statistics. @@ -324,22 +376,37 @@ or bottom half). called when the filesystem is remounted. This is called with the kernel lock held -``clear_inode`` - called then the VFS clears the inode. Optional - ``umount_begin`` called when the VFS is unmounting a filesystem. ``show_options`` - called by the VFS to show mount options for /proc/<pid>/mounts. + called by the VFS to show mount options for /proc/<pid>/mounts + and /proc/<pid>/mountinfo. (see "Mount Options" section) +``show_devname`` + Optional. Called by the VFS to show device name for + /proc/<pid>/{mounts,mountinfo,mountstats}. If not provided then + '(struct mount).mnt_devname' will be used. + +``show_path`` + Optional. Called by the VFS (for /proc/<pid>/mountinfo) to show + the mount root dentry path relative to the filesystem root. + +``show_stats`` + Optional. Called by the VFS (for /proc/<pid>/mountstats) to show + filesystem-specific mount statistics. + ``quota_read`` called by the VFS to read from filesystem quota file. ``quota_write`` called by the VFS to write to filesystem quota file. +``get_dquots`` + called by quota to get 'struct dquot' array for a particular inode. + Optional. + ``nr_cached_objects`` called by the sb cache shrinking function for the filesystem to return the number of freeable cached objects it contains. @@ -1222,7 +1289,7 @@ defined: return -ECHILD and it will be called again in ref-walk mode. -``_weak_revalidate`` +``d_weak_revalidate`` called when the VFS needs to revalidate a "jumped" dentry. This is called when a path-walk ends at dentry that was not acquired by doing a lookup in the parent directory. This includes "/", |