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authorFrederic Weisbecker <fweisbec@gmail.com>2009-05-16 19:10:38 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2009-09-14 07:18:25 +0200
commit08f14fc8963e585e65b71212ce8050607b9b6c36 (patch)
tree04d808f71193df2a90d485fcc0e2604bd8fe8d93 /fs/reiserfs/prints.c
parentc72e05756b900b3be24cd73a16de52bab80984c0 (diff)
downloadlinux-stericsson-08f14fc8963e585e65b71212ce8050607b9b6c36.tar.gz
kill-the-bkl/reiserfs: move the concurrent tree accesses checks per superblock
When do_balance() balances the tree, a trick is performed to provide the ability for other tree writers/readers to check whether do_balance() is executing concurrently (requires CONFIG_REISERFS_CHECK). This is done to protect concurrent accesses to the tree. The trick is the following: When do_balance is called, a unique global variable called cur_tb takes a pointer to the current tree to be rebalanced. Once do_balance finishes its work, cur_tb takes the NULL value. Then, concurrent tree readers/writers just have to check the value of cur_tb to ensure do_balance isn't executing concurrently. If it is, then it proves that schedule() occured on do_balance(), which then relaxed the bkl that protected the tree. Now that the bkl has be turned into a mutex, this check is still fine even though do_balance() becomes preemptible: the write lock will not be automatically released on schedule(), so the tree is still protected. But this is only fine if we have a single reiserfs mountpoint. Indeed, because the bkl is a global lock, it didn't allowed concurrent executions between a tree reader/writer in a mount point and a do_balance() on another tree from another mountpoint. So assuming all these readers/writers weren't supposed to be reentrant, the current check now sometimes detect false positives with the current per-superblock mutex which allows this reentrancy. This patch keeps the concurrent tree accesses check but moves it per superblock, so that only trees from a same mount point are checked to be not accessed concurrently. [ Impact: fix spurious panic while running several reiserfs mount-points ] Cc: Jeff Mahoney <jeffm@suse.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'fs/reiserfs/prints.c')
-rw-r--r--fs/reiserfs/prints.c4
1 files changed, 0 insertions, 4 deletions
diff --git a/fs/reiserfs/prints.c b/fs/reiserfs/prints.c
index 536eacaeb710..adbc6f538515 100644
--- a/fs/reiserfs/prints.c
+++ b/fs/reiserfs/prints.c
@@ -349,10 +349,6 @@ void reiserfs_debug(struct super_block *s, int level, const char *fmt, ...)
. */
-#ifdef CONFIG_REISERFS_CHECK
-extern struct tree_balance *cur_tb;
-#endif
-
void __reiserfs_panic(struct super_block *sb, const char *id,
const char *function, const char *fmt, ...)
{