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authorLinus Torvalds <torvalds@linux-foundation.org>2012-06-08 10:34:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-08 10:34:03 -0700
commit32ba9c3fcab960f0b0d332c86ebcd2c4870d9bb8 (patch)
treecd3638359e7a635dc15856559ac01b14196c4ff7
parent0b35d326f813a654f0cd40f513bd95e3935921c1 (diff)
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Revert "vfs: stop d_splice_alias creating directory aliases"
This reverts commit 7732a557b1342c6e6966efb5f07effcf99f56167 (and commit 3f50fff4dace23d3cfeb195d5cd4ee813cee68b7, which was a follow-up cleanup). We're chasing an elusive bug that Dave Jones can apparently reproduce using his system call fuzzer tool, and that looks like some kind of locking ordering problem on the directory i_mutex chain. Our i_mutex locking is rather complex, and depends on the topological ordering of the directories, which is why we have been very wary of splicing directory entries around. Of course, we really don't want to ever see aliased unconnected directories anyway, so none of this should ever happen, but this revert aims to basically get us back to a known older state. Bruce points to some of the previous discussion at http://marc.info/?i=<20110310105821.GE22723@ZenIV.linux.org.uk> and in particular a long post from Neil: http://marc.info/?i=<20110311150749.2fa2be66@notabene.brown> It should be noted that it's possible that Dave's problems come from other changes altohgether, including possibly just the fact that Dave constantly is teachning his fuzzer new tricks. So what appears to be a new bug could in fact be an old one that just gets newly triggered, but reverting these patches as "still under heavy discussion" is the right thing regardless. Requested-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: J. Bruce Fields <bfields@fieldses.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/dcache.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 85c9e2b..4046904 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -683,6 +683,8 @@ EXPORT_SYMBOL(dget_parent);
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
+ * @want_discon: flag, used by d_splice_alias, to request
+ * that only a DISCONNECTED alias be returned.
*
* If inode has a hashed alias, or is a directory and has any alias,
* acquire the reference to alias and return it. Otherwise return NULL.
@@ -691,9 +693,10 @@ EXPORT_SYMBOL(dget_parent);
* of a filesystem.
*
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
- * any other hashed alias over that.
+ * any other hashed alias over that one unless @want_discon is set,
+ * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
*/
-static struct dentry *__d_find_alias(struct inode *inode)
+static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
{
struct dentry *alias, *discon_alias;
@@ -705,7 +708,7 @@ again:
if (IS_ROOT(alias) &&
(alias->d_flags & DCACHE_DISCONNECTED)) {
discon_alias = alias;
- } else {
+ } else if (!want_discon) {
__dget_dlock(alias);
spin_unlock(&alias->d_lock);
return alias;
@@ -736,7 +739,7 @@ struct dentry *d_find_alias(struct inode *inode)
if (!list_empty(&inode->i_dentry)) {
spin_lock(&inode->i_lock);
- de = __d_find_alias(inode);
+ de = __d_find_alias(inode, 0);
spin_unlock(&inode->i_lock);
}
return de;
@@ -1647,8 +1650,9 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
if (inode && S_ISDIR(inode->i_mode)) {
spin_lock(&inode->i_lock);
- new = __d_find_any_alias(inode);
+ new = __d_find_alias(inode, 1);
if (new) {
+ BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
spin_unlock(&inode->i_lock);
security_d_instantiate(new, inode);
d_move(new, dentry);
@@ -2478,7 +2482,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
struct dentry *alias;
/* Does an aliased dentry already exist? */
- alias = __d_find_alias(inode);
+ alias = __d_find_alias(inode, 0);
if (alias) {
actual = alias;
write_seqlock(&rename_lock);