From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?utf-8?B?SsO2cm4=?= Engel <joern@lazybastard.org>
Subject: [Patch 18/18] fs/logfs/Locking
Date: Sun, 3 Jun 2007 20:51:21 +0200
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Cc: akpm@osdl.org, Sam Ravnborg <sam@ravnborg.org>,
	John Stoffel <john@stoffel.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Jamie Lokier <jamie@shareable.org>,
	Artem Bityutskiy <dedekind@infradead.org>,
	CaT <cat@zip.com.au>, Jan Engelhardt <jengelh@linux01.gwdg.de>,
	Evgeniy Polyakov <johnpol@2ka.mipt.ru>,
	David Weinehall <tao@acc.umu.se>,
	Arnd Bergmann <arnd@arndb.de>, Willy Tarreau <w@1wt.eu>,
	Kyle Moffett <mrmacman_g4@mac.com>,
	Dongjun Shin <djshin90@gmail.com>, Pavel Machek <pavel@ucw.cz>,
	Bill Davidsen <davidsen@tmr.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Albert Cahalan <acahalan@gmail.com>,
	Pekka Enberg <penberg@cs.helsinki.fi>,
	Roland Dreier <rdreier@cisco.com>,
	Ondrej Zajicek <santiago@crfreenet.org>,
	Ulisses Furquim <ulissesf@gmail.com>
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--- /dev/null	2007-03-13 19:15:28.862769062 +0100
+++ linux-2.6.21logfs/fs/logfs/Locking	2007-06-03 19:18:57.000000000 +0200
@@ -0,0 +1,45 @@
+Locks:
+
+s_victim_mutex
+Protects victim inode for create, unlink, mkdir, rmdir, mknod, link,
+symlink and one variant of rename.  Only one victim inode may exist at
+a time.  In case of unclean unmount, victim inode has to be deleted
+before next read-writable mount.
+
+s_rename_mutex
+Protects victim dd for rename.  Only one victim dd may exist at a
+time.  In case of unclean unmount, victim dd has to be deleted before
+next read-writable mount.
+
+s_write_inode_mutex
+Taken when writing an inode.  Deleted inodes can be locked, preventing
+further iget operations during writeout.  Logfs may need to iget the
+inode for garbage collection, so the inode in question needs to be
+stored in the superblock and used directly without calling iget.
+
+s_log_sem
+Used for allocating space in journal.
+
+s_r_sem
+Protects the memory required for reads from the filesystem.
+
+s_w_sem
+Protects the memory required for writes to the filesystem.
+
+s_ino_lock
+Protects s_last_ino.
+
+
+Lock order:
+s_rename_mutex --> s_victim_mutex
+s_rename_mutex --> s_write_inode_mutex
+s_rename_mutex --> s_w_sem
+
+s_victim_mutex --> s_write_inode_mutex
+s_victim_mutex --> s_w_sem
+s_victim_mutex --> s_ino_lock
+
+s_write_inode_mutex --> s_w_sem
+
+s_w_sem --> s_log_sem
+s_w_sem --> s_r_sem