[PATCH] docs: fs: Refactor directory-locking.rst for better reading

From: Kari Argillander
Date: Mon Aug 16 2021 - 18:26:58 EST


Reorganize classes so that it is easier to read. Before number 4 was
written in one lenghty paragraph. It is as long as number 6 and it is
basically same kind of class (rename()). Also old number 5 was list and
it is as short as 1, 2, 3 so it can be converted non list.

This makes file now much readible.

Signed-off-by: Kari Argillander <kari.argillander@xxxxxxxxx>
---
.../filesystems/directory-locking.rst | 31 +++++++++----------
1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/Documentation/filesystems/directory-locking.rst b/Documentation/filesystems/directory-locking.rst
index 504ba940c36c..33921dff7af4 100644
--- a/Documentation/filesystems/directory-locking.rst
+++ b/Documentation/filesystems/directory-locking.rst
@@ -11,7 +11,7 @@ When taking the i_rwsem on multiple non-directory objects, we
always acquire the locks in order by increasing address. We'll call
that "inode pointer" order in the following.

-For our purposes all operations fall in 5 classes:
+For our purposes all operations fall in 6 classes:

1) read access. Locking rules: caller locks directory we are accessing.
The lock is taken shared.
@@ -22,26 +22,25 @@ exclusive.
3) object removal. Locking rules: caller locks parent, finds victim,
locks victim and calls the method. Locks are exclusive.

-4) rename() that is _not_ cross-directory. Locking rules: caller locks
-the parent and finds source and target. In case of exchange (with
-RENAME_EXCHANGE in flags argument) lock both. In any case,
-if the target already exists, lock it. If the source is a non-directory,
-lock it. If we need to lock both, lock them in inode pointer order.
-Then call the method. All locks are exclusive.
-NB: we might get away with locking the source (and target in exchange
-case) shared.
+4) link creation. Locking rules: lock parent, check that source is not
+a directory, lock source and call the method. Locks are exclusive.

-5) link creation. Locking rules:
+5) rename() that is _not_ cross-directory.
+Locking rules:

- * lock parent
- * check that source is not a directory
- * lock source
- * call the method.
+ * Caller locks the parent and finds source and target.
+ * In case of exchange (with RENAME_EXCHANGE in flags argument)
+ lock both the source and the target.
+ * If the target exists, lock it, If the source is a non-directory,
+ lock it. If we need to lock both, do so in inode pointer order.
+ * Call the method.

All locks are exclusive.
+NB: we might get away with locking the source (and target in exchange
+case) shared.

-6) cross-directory rename. The trickiest in the whole bunch. Locking
-rules:
+6) rename() that _is_ cross-directory. The trickiest in the whole bunch.
+Locking rules:

* lock the filesystem
* lock parents in "ancestors first" order.
--
2.30.2