[Patch 18/18] fs/logfs/Locking
Jörn Engel
joern at lazybastard.org
Sun Jun 3 17:21:07 EDT 2007
--- /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
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