docs: filesystems: vfs: actualize struct super_operations description
Added/updated descriptions for super_operations:
- free_inode method
- evict_inode method
- freeze_super/thaw_super method
- show_{devname,path,stats} procfs-related methods
- get_dquots method
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230313130718.253708-3-aleksandr.mikhalitsyn@canonical.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Alexander Mikhalitsyn
Jonathan Corbet
parent
85bf9a0ee2
commit
592d80727f
@ -245,33 +245,42 @@ struct super_operations
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-----------------------
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This describes how the VFS can manipulate the superblock of your
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filesystem. As of kernel 2.6.22, the following members are defined:
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filesystem. The following members are defined:
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.. code-block:: c
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struct super_operations {
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struct inode *(*alloc_inode)(struct super_block *sb);
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void (*destroy_inode)(struct inode *);
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void (*free_inode)(struct inode *);
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void (*dirty_inode) (struct inode *, int flags);
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int (*write_inode) (struct inode *, int);
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void (*drop_inode) (struct inode *);
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void (*delete_inode) (struct inode *);
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int (*write_inode) (struct inode *, struct writeback_control *wbc);
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int (*drop_inode) (struct inode *);
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void (*evict_inode) (struct inode *);
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void (*put_super) (struct super_block *);
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int (*sync_fs)(struct super_block *sb, int wait);
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int (*freeze_super) (struct super_block *);
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int (*freeze_fs) (struct super_block *);
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int (*thaw_super) (struct super_block *);
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int (*unfreeze_fs) (struct super_block *);
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int (*statfs) (struct dentry *, struct kstatfs *);
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int (*remount_fs) (struct super_block *, int *, char *);
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void (*clear_inode) (struct inode *);
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void (*umount_begin) (struct super_block *);
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int (*show_options)(struct seq_file *, struct dentry *);
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int (*show_devname)(struct seq_file *, struct dentry *);
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int (*show_path)(struct seq_file *, struct dentry *);
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int (*show_stats)(struct seq_file *, struct dentry *);
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ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
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ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
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int (*nr_cached_objects)(struct super_block *);
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void (*free_cached_objects)(struct super_block *, int);
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struct dquot **(*get_dquots)(struct inode *);
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long (*nr_cached_objects)(struct super_block *,
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struct shrink_control *);
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long (*free_cached_objects)(struct super_block *,
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struct shrink_control *);
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};
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All methods are called without any locks being held, unless otherwise
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@ -292,6 +301,11 @@ or bottom half).
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->alloc_inode was defined and simply undoes anything done by
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->alloc_inode.
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``free_inode``
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this method is called from RCU callback. If you use call_rcu()
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in ->destroy_inode to free 'struct inode' memory, then it's
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better to release memory in this method.
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``dirty_inode``
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this method is called by the VFS when an inode is marked dirty.
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This is specifically for the inode itself being marked dirty,
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@ -319,8 +333,12 @@ or bottom half).
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practice of using "force_delete" in the put_inode() case, but
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does not have the races that the "force_delete()" approach had.
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``delete_inode``
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called when the VFS wants to delete an inode
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``evict_inode``
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called when the VFS wants to evict an inode. Caller does
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*not* evict the pagecache or inode-associated metadata buffers;
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the method has to use truncate_inode_pages_final() to get rid
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of those. Caller makes sure async writeback cannot be running for
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the inode while (or after) ->evict_inode() is called. Optional.
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``put_super``
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called when the VFS wishes to free the superblock
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@ -331,14 +349,25 @@ or bottom half).
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superblock. The second parameter indicates whether the method
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should wait until the write out has been completed. Optional.
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``freeze_super``
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Called instead of ->freeze_fs callback if provided.
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Main difference is that ->freeze_super is called without taking
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down_write(&sb->s_umount). If filesystem implements it and wants
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->freeze_fs to be called too, then it has to call ->freeze_fs
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explicitly from this callback. Optional.
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``freeze_fs``
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called when VFS is locking a filesystem and forcing it into a
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consistent state. This method is currently used by the Logical
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Volume Manager (LVM).
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Volume Manager (LVM) and ioctl(FIFREEZE). Optional.
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``thaw_super``
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called when VFS is unlocking a filesystem and making it writable
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again after ->freeze_super. Optional.
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``unfreeze_fs``
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called when VFS is unlocking a filesystem and making it writable
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again.
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again after ->freeze_fs. Optional.
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``statfs``
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called when the VFS needs to get filesystem statistics.
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@ -347,22 +376,37 @@ or bottom half).
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called when the filesystem is remounted. This is called with
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the kernel lock held
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``clear_inode``
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called then the VFS clears the inode. Optional
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``umount_begin``
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called when the VFS is unmounting a filesystem.
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``show_options``
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called by the VFS to show mount options for /proc/<pid>/mounts.
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called by the VFS to show mount options for /proc/<pid>/mounts
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and /proc/<pid>/mountinfo.
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(see "Mount Options" section)
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``show_devname``
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Optional. Called by the VFS to show device name for
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/proc/<pid>/{mounts,mountinfo,mountstats}. If not provided then
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'(struct mount).mnt_devname' will be used.
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``show_path``
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Optional. Called by the VFS (for /proc/<pid>/mountinfo) to show
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the mount root dentry path relative to the filesystem root.
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``show_stats``
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Optional. Called by the VFS (for /proc/<pid>/mountstats) to show
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filesystem-specific mount statistics.
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``quota_read``
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called by the VFS to read from filesystem quota file.
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``quota_write``
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called by the VFS to write to filesystem quota file.
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``get_dquots``
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called by quota to get 'struct dquot' array for a particular inode.
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Optional.
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``nr_cached_objects``
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called by the sb cache shrinking function for the filesystem to
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return the number of freeable cached objects it contains.
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