Author: kib
Date: Sun Jan 15 00:46:29 2012
New Revision: 230124
URL: http://svn.freebsd.org/changeset/base/230124
Log:
MFC r229828:
Avoid LOR between vfs_busy() lock and covered vnode lock on quotaon().
Modified:
stable/9/sys/kern/vfs_syscalls.c
stable/9/sys/ufs/ufs/ufs_quota.c
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/kern/vfs_syscalls.c
==============================================================================
--- stable/9/sys/kern/vfs_syscalls.c Sun Jan 15 00:08:14 2012
(r230123)
+++ stable/9/sys/kern/vfs_syscalls.c Sun Jan 15 00:46:29 2012
(r230124)
@@ -86,6 +86,8 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_page.h>
#include <vm/uma.h>
+#include <ufs/ufs/quota.h>
+
static MALLOC_DEFINE(M_FADVISE, "fadvise", "posix_fadvise(2) information");
SDT_PROVIDER_DEFINE(vfs);
@@ -212,7 +214,20 @@ sys_quotactl(td, uap)
return (error);
}
error = VFS_QUOTACTL(mp, uap->cmd, uap->uid, uap->arg);
- vfs_unbusy(mp);
+
+ /*
+ * Since quota on operation typically needs to open quota
+ * file, the Q_QUOTAON handler needs to unbusy the mount point
+ * before calling into namei. Otherwise, unmount might be
+ * started between two vfs_busy() invocations (first is our,
+ * second is from mount point cross-walk code in lookup()),
+ * causing deadlock.
+ *
+ * Require that Q_QUOTAON handles the vfs_busy() reference on
+ * its own, always returning with ubusied mount point.
+ */
+ if ((uap->cmd >> SUBCMDSHIFT) != Q_QUOTAON)
+ vfs_unbusy(mp);
VFS_UNLOCK_GIANT(vfslocked);
return (error);
}
Modified: stable/9/sys/ufs/ufs/ufs_quota.c
==============================================================================
--- stable/9/sys/ufs/ufs/ufs_quota.c Sun Jan 15 00:08:14 2012
(r230123)
+++ stable/9/sys/ufs/ufs/ufs_quota.c Sun Jan 15 00:46:29 2012
(r230124)
@@ -512,17 +512,29 @@ quotaon(struct thread *td, struct mount
NDINIT(&nd, LOOKUP, FOLLOW | MPSAFE, UIO_USERSPACE, fname, td);
flags = FREAD | FWRITE;
+ vfs_ref(mp);
+ vfs_unbusy(mp);
error = vn_open(&nd, &flags, 0, NULL);
- if (error)
+ if (error != 0) {
+ vfs_rel(mp);
return (error);
+ }
vfslocked = NDHASGIANT(&nd);
NDFREE(&nd, NDF_ONLY_PNBUF);
vp = nd.ni_vp;
- if (vp->v_type != VREG) {
+ error = vfs_busy(mp, MBF_NOWAIT);
+ vfs_rel(mp);
+ if (error == 0) {
+ if (vp->v_type != VREG) {
+ error = EACCES;
+ vfs_unbusy(mp);
+ }
+ }
+ if (error != 0) {
VOP_UNLOCK(vp, 0);
(void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
VFS_UNLOCK_GIANT(vfslocked);
- return (EACCES);
+ return (error);
}
UFS_LOCK(ump);
@@ -531,6 +543,7 @@ quotaon(struct thread *td, struct mount
VOP_UNLOCK(vp, 0);
(void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
VFS_UNLOCK_GIANT(vfslocked);
+ vfs_unbusy(mp);
return (EALREADY);
}
ump->um_qflags[type] |= QTF_OPENING|QTF_CLOSING;
@@ -542,6 +555,7 @@ quotaon(struct thread *td, struct mount
UFS_UNLOCK(ump);
(void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
VFS_UNLOCK_GIANT(vfslocked);
+ vfs_unbusy(mp);
return (error);
}
VOP_UNLOCK(vp, 0);
@@ -619,6 +633,7 @@ again:
("quotaon: leaking flags"));
UFS_UNLOCK(ump);
+ vfs_unbusy(mp);
return (error);
}
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