Documentation/filesystems/directory-locking.rst

7 kinds of locks - per-inode (->i_rwsem) and per-filesystem
55 	* lock the filesystem
96 and fail the lookup if it is.  Then we try to lock the filesystem and the
101 Note that splicing does *not* involve any modification of the filesystem;
104 filesystem lock prevents any changes of tree topology, other than having a
107 the filesystem lock, their relationship will remain unchanged until
114 Multiple-filesystem stuff
118 another filesystem; it may be ecryptfs doing operation in the underlying
119 filesystem, overlayfs doing something to the layers, network filesystem
122 directory operation on this filesystem might involve directory operations
123 on that filesystem" should be an asymmetric relation (or, if you will,
125 on a filesystem could trigger directory operations only on higher-ranked
127 filesystem ranks lower than whatever it caches on, etc.)
140   * rank ->i_rwsem of non-directories on given filesystem in inode pointer
142   * put ->i_rwsem of all directories on a filesystem at the same rank,
143     lower than ->i_rwsem of any non-directory on the same filesystem.
145     on the same filesystem.
149 For example, if we have NFS filesystem caching on a local one, we have
151   1. ->s_vfs_rename_mutex of NFS filesystem
152   2. ->i_rwsem of directories on that NFS filesystem, same rank for all
153   3. ->i_rwsem of non-directories on that filesystem, in order of
155   4. ->s_vfs_rename_mutex of local filesystem
156   5. ->i_rwsem of directories on the local filesystem, same rank for all
157   6. ->i_rwsem of non-directories on local filesystem, in order of
169 i.e. they all will be ->i_rwsem of directories on the same filesystem.
171 are done directly to that filesystem and none of them has actually
199 Since all operations are on the same filesystem, there can't be
209 has acquired filesystem lock and verified that directories involved have