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cifs: reduce false positives with inode aliasing serverino autodisable

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It turns out that not all directory inodes with dentries on the
i_dentry list are unusable here. We only consider them unusable if they
are still hashed or if they have a root dentry attached.

Full disclosure -- this check is inherently racy. There's nothing that
stops someone from slapping a new dentry onto this inode just after
this check, or hashing an existing one that's already attached. So,
this is really a "best effort" thing to work around misbehaving servers.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This commit is contained in:
Jeff Layton 2010-08-02 17:43:54 -04:00 committed by Steve French
parent 67b7626a05
commit 5acfec2502
1 changed files with 31 additions and 12 deletions
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43
fs/cifs/inode.c
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@ -732,15 +732,9 @@ cifs_find_inode(struct inode *inode, void *opaque)
if ((inode->i_mode & S_IFMT) != (fattr->cf_mode & S_IFMT))
return 0;
/*
* uh oh -- it's a directory. We can't use it since hardlinked dirs are
* verboten. Disable serverino and return it as if it were found, the
* caller can discard it, generate a uniqueid and retry the find
*/
if (S_ISDIR(inode->i_mode) && !list_empty(&inode->i_dentry)) {
/* if it's not a directory or has no dentries, then flag it */
if (S_ISDIR(inode->i_mode) && !list_empty(&inode->i_dentry))
fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;
cifs_autodisable_serverino(CIFS_SB(inode->i_sb));
}
return 1;
}
@ -754,6 +748,27 @@ cifs_init_inode(struct inode *inode, void *opaque)
return 0;
}
/*
* walk dentry list for an inode and report whether it has aliases that
* are hashed. We use this to determine if a directory inode can actually
* be used.
*/
static bool
inode_has_hashed_dentries(struct inode *inode)
{
struct dentry *dentry;
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
if (!d_unhashed(dentry) || IS_ROOT(dentry)) {
spin_unlock(&dcache_lock);
return true;
}
}
spin_unlock(&dcache_lock);
return false;
}
/* Given fattrs, get a corresponding inode */
struct inode *
cifs_iget(struct super_block *sb, struct cifs_fattr *fattr)
@ -769,12 +784,16 @@ retry_iget5_locked:
inode = iget5_locked(sb, hash, cifs_find_inode, cifs_init_inode, fattr);
if (inode) {
/* was there a problematic inode number collision? */
/* was there a potentially problematic inode collision? */
if (fattr->cf_flags & CIFS_FATTR_INO_COLLISION) {
iput(inode);
fattr->cf_uniqueid = iunique(sb, ROOT_I);
fattr->cf_flags &= ~CIFS_FATTR_INO_COLLISION;
goto retry_iget5_locked;
if (inode_has_hashed_dentries(inode)) {
cifs_autodisable_serverino(CIFS_SB(sb));
iput(inode);
fattr->cf_uniqueid = iunique(sb, ROOT_I);
goto retry_iget5_locked;
}
}
cifs_fattr_to_inode(inode, fattr);