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configfs: Protect configfs_dirent s_links list mutations

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Symlinks to a config_item are listed under its configfs_dirent s_links, but the
list mutations are not protected by any common lock.

This patch uses the configfs_dirent_lock spinlock to add the necessary
protection.

Note: we should also protect the list_empty() test in configfs_detach_prep() but
1/ the lock should not be released immediately because nothing would prevent the
list from being filled after a successful list_empty() test, making the problem
tricky,
2/ this will be solved by the rmdir() vs rename() deadlock bugfix.

Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This commit is contained in:
Louis Rilling
2008-06-16 19:00:59 +02:00
committed by Mark Fasheh
parent 6f61076406
commit 5301a77da2
2 changed files with 9 additions and 4 deletions
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5
fs/configfs/dir.c
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@@ -37,10 +37,11 @@
DECLARE_RWSEM(configfs_rename_sem);
/*
* Protects mutations of configfs_dirent linkage together with proper i_mutex
* Also protects mutations of symlinks linkage to target configfs_dirent
* Mutators of configfs_dirent linkage must *both* have the proper inode locked
* and configfs_dirent_lock locked, in that order.
* This allows one to safely traverse configfs_dirent trees without having to
* lock inodes.
* This allows one to safely traverse configfs_dirent trees and symlinks without
* having to lock inodes.
*/
DEFINE_SPINLOCK(configfs_dirent_lock);