[PATCH] v9fs: fix races in fid allocation

Fid management cleanup.  The patch attempts to fix the races in dentry's
fid management.

Dentries don't keep the opened fids anymore, they are moved to the file
structs.  Ideally there should be no more than one fid with fidcreate equal
to zero in the dentry's list of fids.

v9fs_fid_create initializes the important fields (fid, fidcreated) before
v9fs_fid is added to the list.  v9fs_fid_lookup returns only fids that are
not created by v9fs_create.  v9fs_fid_get_created returns the fid created
by the same process by v9fs_create (if any) and removes it from dentry's
list

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 59 insertions, 32 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index b16322db5ce6..2b696ae6655a 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -307,7 +307,7 @@ v9fs_create(struct inode *dir,
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
 	struct super_block *sb = dir->i_sb;
 	struct v9fs_fid *dirfid =
-	    v9fs_fid_lookup(file_dentry->d_parent, FID_WALK);
+	    v9fs_fid_lookup(file_dentry->d_parent);
 	struct v9fs_fid *fid = NULL;
 	struct inode *file_inode = NULL;
 	struct v9fs_fcall *fcall = NULL;
@@ -317,6 +317,7 @@ v9fs_create(struct inode *dir,
 	long newfid = -1;
 	int result = 0;
 	unsigned int iounit = 0;
+	int wfidno = -1;
 
 	perm = unixmode2p9mode(v9ses, perm);
 
@@ -350,7 +351,7 @@ v9fs_create(struct inode *dir,
 	if (result < 0) {
 		dprintk(DEBUG_ERROR, "clone error: %s\n", FCALL_ERROR(fcall));
 		v9fs_put_idpool(newfid, &v9ses->fidpool);
-		newfid = 0;
+		newfid = -1;
 		goto CleanUpFid;
 	}
 
@@ -369,20 +370,39 @@ v9fs_create(struct inode *dir,
 	qid = fcall->params.rcreate.qid;
 	kfree(fcall);
 
-	fid = v9fs_fid_create(file_dentry);
+	fid = v9fs_fid_create(file_dentry, v9ses, newfid, 1);
+	dprintk(DEBUG_VFS, "fid %p %d\n", fid, fid->fidcreate);
 	if (!fid) {
 		result = -ENOMEM;
 		goto CleanUpFid;
 	}
 
-	fid->fid = newfid;
-	fid->fidopen = 0;
-	fid->fidcreate = 1;
 	fid->qid = qid;
 	fid->iounit = iounit;
-	fid->rdir_pos = 0;
-	fid->rdir_fcall = NULL;
-	fid->v9ses = v9ses;
+
+	/* walk to the newly created file and put the fid in the dentry */
+	wfidno = v9fs_get_idpool(&v9ses->fidpool);
+	if (newfid < 0) {
+		eprintk(KERN_WARNING, "no free fids available\n");
+		return -ENOSPC;
+	}
+
+	result = v9fs_t_walk(v9ses, dirfidnum, wfidno,
+		(char *) file_dentry->d_name.name, NULL);
+	if (result < 0) {
+		dprintk(DEBUG_ERROR, "clone error: %s\n", FCALL_ERROR(fcall));
+		v9fs_put_idpool(wfidno, &v9ses->fidpool);
+		wfidno = -1;
+		goto CleanUpFid;
+	}
+
+	if (!v9fs_fid_create(file_dentry, v9ses, wfidno, 0)) {
+		if (!v9fs_t_clunk(v9ses, newfid, &fcall)) {
+			v9fs_put_idpool(wfidno, &v9ses->fidpool);
+		}
+
+		goto CleanUpFid;
+	}
 
 	if ((perm & V9FS_DMSYMLINK) || (perm & V9FS_DMLINK) ||
 	    (perm & V9FS_DMNAMEDPIPE) || (perm & V9FS_DMSOCKET) ||
@@ -410,11 +430,11 @@ v9fs_create(struct inode *dir,
 	d_instantiate(file_dentry, file_inode);
 
 	if (perm & V9FS_DMDIR) {
-		if (v9fs_t_clunk(v9ses, newfid, &fcall))
+		if (!v9fs_t_clunk(v9ses, newfid, &fcall))
+			v9fs_put_idpool(newfid, &v9ses->fidpool);
+		else
 			dprintk(DEBUG_ERROR, "clunk for mkdir failed: %s\n",
 				FCALL_ERROR(fcall));
-
-		v9fs_put_idpool(newfid, &v9ses->fidpool);
 		kfree(fcall);
 		fid->fidopen = 0;
 		fid->fidcreate = 0;
@@ -426,12 +446,22 @@ v9fs_create(struct inode *dir,
       CleanUpFid:
 	kfree(fcall);
 
-	if (newfid) {
-		if (v9fs_t_clunk(v9ses, newfid, &fcall))
+	if (newfid >= 0) {
+		if (!v9fs_t_clunk(v9ses, newfid, &fcall))
+			v9fs_put_idpool(newfid, &v9ses->fidpool);
+		else
+			dprintk(DEBUG_ERROR, "clunk failed: %s\n",
+				FCALL_ERROR(fcall));
+
+		kfree(fcall);
+	}
+	if (wfidno >= 0) {
+		if (!v9fs_t_clunk(v9ses, wfidno, &fcall))
+			v9fs_put_idpool(wfidno, &v9ses->fidpool);
+		else
 			dprintk(DEBUG_ERROR, "clunk failed: %s\n",
 				FCALL_ERROR(fcall));
 
-		v9fs_put_idpool(newfid, &v9ses->fidpool);
 		kfree(fcall);
 	}
 	return result;
@@ -461,7 +491,7 @@ static int v9fs_remove(struct inode *dir, struct dentry *file, int rmdir)
 	file_inode = file->d_inode;
 	sb = file_inode->i_sb;
 	v9ses = v9fs_inode2v9ses(file_inode);
-	v9fid = v9fs_fid_lookup(file, FID_OP);
+	v9fid = v9fs_fid_lookup(file);
 
 	if (!v9fid) {
 		dprintk(DEBUG_ERROR,
@@ -545,7 +575,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
 	sb = dir->i_sb;
 	v9ses = v9fs_inode2v9ses(dir);
-	dirfid = v9fs_fid_lookup(dentry->d_parent, FID_WALK);
+	dirfid = v9fs_fid_lookup(dentry->d_parent);
 
 	if (!dirfid) {
 		dprintk(DEBUG_ERROR, "no dirfid\n");
@@ -573,7 +603,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 		v9fs_put_idpool(newfid, &v9ses->fidpool);
 		if (result == -ENOENT) {
 			d_add(dentry, NULL);
-			dprintk(DEBUG_ERROR,
+			dprintk(DEBUG_VFS,
 				"Return negative dentry %p count %d\n",
 				dentry, atomic_read(&dentry->d_count));
 			return NULL;
@@ -601,16 +631,13 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
 	inode->i_ino = v9fs_qid2ino(&fcall->params.rstat.stat->qid);
 
-	fid = v9fs_fid_create(dentry);
+	fid = v9fs_fid_create(dentry, v9ses, newfid, 0);
 	if (fid == NULL) {
 		dprintk(DEBUG_ERROR, "couldn't insert\n");
 		result = -ENOMEM;
 		goto FreeFcall;
 	}
 
-	fid->fid = newfid;
-	fid->fidopen = 0;
-	fid->v9ses = v9ses;
 	fid->qid = fcall->params.rstat.stat->qid;
 
 	dentry->d_op = &v9fs_dentry_operations;
@@ -665,11 +692,11 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 {
 	struct inode *old_inode = old_dentry->d_inode;
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(old_inode);
-	struct v9fs_fid *oldfid = v9fs_fid_lookup(old_dentry, FID_WALK);
+	struct v9fs_fid *oldfid = v9fs_fid_lookup(old_dentry);
 	struct v9fs_fid *olddirfid =
-	    v9fs_fid_lookup(old_dentry->d_parent, FID_WALK);
+	    v9fs_fid_lookup(old_dentry->d_parent);
 	struct v9fs_fid *newdirfid =
-	    v9fs_fid_lookup(new_dentry->d_parent, FID_WALK);
+	    v9fs_fid_lookup(new_dentry->d_parent);
 	struct v9fs_stat *mistat = kmalloc(v9ses->maxdata, GFP_KERNEL);
 	struct v9fs_fcall *fcall = NULL;
 	int fid = -1;
@@ -744,7 +771,7 @@ v9fs_vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 {
 	struct v9fs_fcall *fcall = NULL;
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
-	struct v9fs_fid *fid = v9fs_fid_lookup(dentry, FID_OP);
+	struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
 	int err = -EPERM;
 
 	dprintk(DEBUG_VFS, "dentry: %p\n", dentry);
@@ -778,7 +805,7 @@ v9fs_vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
 {
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
-	struct v9fs_fid *fid = v9fs_fid_lookup(dentry, FID_OP);
+	struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
 	struct v9fs_fcall *fcall = NULL;
 	struct v9fs_stat *mistat = kmalloc(v9ses->maxdata, GFP_KERNEL);
 	int res = -EPERM;
@@ -960,7 +987,7 @@ v9fs_vfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
 	if (retval != 0)
 		goto FreeFcall;
 
-	newfid = v9fs_fid_lookup(dentry, FID_OP);
+	newfid = v9fs_fid_lookup(dentry);
 
 	/* issue a twstat */
 	v9fs_blank_mistat(v9ses, mistat);
@@ -1004,7 +1031,7 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
 
 	struct v9fs_fcall *fcall = NULL;
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
-	struct v9fs_fid *fid = v9fs_fid_lookup(dentry, FID_OP);
+	struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
 
 	if (!fid) {
 		dprintk(DEBUG_ERROR, "could not resolve fid from dentry\n");
@@ -1148,7 +1175,7 @@ v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
 	struct v9fs_fcall *fcall = NULL;
 	struct v9fs_stat *mistat = kmalloc(v9ses->maxdata, GFP_KERNEL);
-	struct v9fs_fid *oldfid = v9fs_fid_lookup(old_dentry, FID_OP);
+	struct v9fs_fid *oldfid = v9fs_fid_lookup(old_dentry);
 	struct v9fs_fid *newfid = NULL;
 	char *symname = __getname();
 
@@ -1168,7 +1195,7 @@ v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
 	if (retval != 0)
 		goto FreeMem;
 
-	newfid = v9fs_fid_lookup(dentry, FID_OP);
+	newfid = v9fs_fid_lookup(dentry);
 	if (!newfid) {
 		dprintk(DEBUG_ERROR, "couldn't resolve fid from dentry\n");
 		goto FreeMem;
@@ -1246,7 +1273,7 @@ v9fs_vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
 	if (retval != 0)
 		goto FreeMem;
 
-	newfid = v9fs_fid_lookup(dentry, FID_OP);
+	newfid = v9fs_fid_lookup(dentry);
 	if (!newfid) {
 		dprintk(DEBUG_ERROR, "coudn't resove fid from dentry\n");
 		retval = -EINVAL;