From: Matt Benjamin <matt@linuxbox.com>
Date: Wed, 24 Aug 2011 20:23:37 +0000 (-0400)
Subject: LINUX  vcache lock ordering in afs_linux_readdir
X-Git-Tag: openafs-devel-1_7_1~112
X-Git-Url: https://git.openafs.org/?p=openafs.git;a=commitdiff_plain;h=fa97579a08cdf23fcff3c50a5845d72a785feeaf

LINUX  vcache lock ordering in afs_linux_readdir

Normalize shared and exclusive lock operations.  Take the lock
exclusive immediately, since the code assumes a write lock if
the vcache state is in flux or the entry is being fetched, releasing
-write- rather than shared, since we do not hold a shared lock.

Change-Id: Icbffdf21c6fc7929483589e87ffe9131834c79b4
Reviewed-on: http://gerrit.openafs.org/5309
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
---

diff --git a/src/afs/LINUX/osi_vnodeops.c b/src/afs/LINUX/osi_vnodeops.c
index f7d5277..57dc081 100644
--- a/src/afs/LINUX/osi_vnodeops.c
+++ b/src/afs/LINUX/osi_vnodeops.c
@@ -296,8 +296,7 @@ afs_linux_readdir(struct file *fp, void *dirbuf, filldir_t filldir)
 	code = -ENOENT;
 	goto out;
     }
-    ObtainSharedLock(&avc->lock, 810);
-    UpgradeSToWLock(&avc->lock, 811);
+    ObtainWriteLock(&avc->lock, 811);
     ObtainReadLock(&tdc->lock);
     /*
      * Make sure that the data in the cache is current. There are two
@@ -309,15 +308,15 @@ afs_linux_readdir(struct file *fp, void *dirbuf, filldir_t filldir)
 	   && (tdc->dflags & DFFetching)
 	   && hsame(avc->f.m.DataVersion, tdc->f.versionNo)) {
 	ReleaseReadLock(&tdc->lock);
-	ReleaseSharedLock(&avc->lock);
+	ReleaseWriteLock(&avc->lock);
 	afs_osi_Sleep(&tdc->validPos);
-	ObtainSharedLock(&avc->lock, 812);
+	ObtainWriteLock(&avc->lock, 812);
 	ObtainReadLock(&tdc->lock);
     }
     if (!(avc->f.states & CStatd)
 	|| !hsame(avc->f.m.DataVersion, tdc->f.versionNo)) {
 	ReleaseReadLock(&tdc->lock);
-	ReleaseSharedLock(&avc->lock);
+	ReleaseWriteLock(&avc->lock);
 	afs_PutDCache(tdc);
 	goto tagain;
     }