distributed filesystems
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Reply-To: trond.myklebust@fys.uio.no
From: Trond Myklebust <trond.myklebust@fys.uio.no>
The following is the fix for the open(".")/open("..") problems
that are hitting distributed file systems such as OpenGFS, and NFS.
The problem is that in the case where the final element of a path is
'.' or '..', then link_path_walk() does not actually check that the
resulting dentry is valid.
For the case of NFS, this results in 2 breakages:
- Resulting dentry may be stale, and so the open() may succeed, but
still results in an invalid file.
- Attribute and data cache checking upon open(), which is normally
done as part of the lookup process, gets circumvented, and so you
end up with strange inconsistencies.
Typical result is 'ls -l' returning "file 'blah' does not exist"
errors.
Cheers,
Trond
diff -u --recursive --new-file linux-2.5.3/fs/namei.c linux-2.5.3-cto/fs/namei.c
--- linux-2.5.3/fs/namei.c Tue Jan 15 22:53:51 2002
+++ linux-2.5.3-cto/fs/namei.c Fri Feb 1 13:00:39 2002
@@ -457,7 +457,7 @@
while (*name=='/')
name++;
if (!*name)
- goto return_base;
+ goto return_reval;
inode = nd->dentry->d_inode;
if (current->link_count)
@@ -576,7 +576,7 @@
inode = nd->dentry->d_inode;
/* fallthrough */
case 1:
- goto return_base;
+ goto return_reval;
}
if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
err = nd->dentry->d_op->d_hash(nd->dentry, &this);
@@ -627,6 +627,19 @@
nd->last_type = LAST_DOT;
else if (this.len == 2 && this.name[1] == '.')
nd->last_type = LAST_DOTDOT;
+return_reval:
+ /*
+ * We bypassed the ordinary revalidation routines.
+ * Check the cached dentry for staleness.
+ */
+ dentry = nd->dentry;
+ if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
+ err = -ESTALE;
+ if (!dentry->d_op->d_revalidate(dentry, 0)) {
+ d_invalidate(dentry);
+ break;
+ }
+ }
return_base:
return 0;
out_dput:
-
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This archive was generated by hypermail 2b29 : Thu Feb 07 2002 - 21:00:13 EST