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https://git.FreeBSD.org/src.git
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Prevent tmpfs_rename() deadlock in a way similar to UFS
Unlock vnodes and try to lock them one by one. Relookup fvp and tvp. Approved by: mdf (mentor)
This commit is contained in:
Gleb Kurtsou
parent
ca846258e2
commit
db94ad126a
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=232960
@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/proc.h>
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#include <sys/stat.h>
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#include <sys/systm.h>
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#include <sys/sysctl.h>
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#include <sys/vnode.h>
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#include <sys/vmmeter.h>
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@ -56,6 +57,8 @@ __FBSDID("$FreeBSD$");
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#include <fs/tmpfs/tmpfs_fifoops.h>
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#include <fs/tmpfs/tmpfs_vnops.h>
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SYSCTL_NODE(_vfs, OID_AUTO, tmpfs, CTLFLAG_RW, 0, "tmpfs file system");
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/* --------------------------------------------------------------------- */
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/*
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@ -46,6 +46,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/sf_buf.h>
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#include <sys/stat.h>
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#include <sys/systm.h>
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#include <sys/sysctl.h>
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#include <sys/unistd.h>
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#include <sys/vnode.h>
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@ -57,6 +58,13 @@ __FBSDID("$FreeBSD$");
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#include <fs/tmpfs/tmpfs_vnops.h>
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#include <fs/tmpfs/tmpfs.h>
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SYSCTL_DECL(_vfs_tmpfs);
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static volatile int tmpfs_rename_restarts;
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SYSCTL_INT(_vfs_tmpfs, OID_AUTO, rename_restarts, CTLFLAG_RD,
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__DEVOLATILE(int *, &tmpfs_rename_restarts), 0,
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"Times rename had to restart due to lock contention");
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/* --------------------------------------------------------------------- */
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static int
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@ -918,6 +926,139 @@ tmpfs_link(struct vop_link_args *v)
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/* --------------------------------------------------------------------- */
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/*
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* We acquire all but fdvp locks using non-blocking acquisitions. If we
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* fail to acquire any lock in the path we will drop all held locks,
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* acquire the new lock in a blocking fashion, and then release it and
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* restart the rename. This acquire/release step ensures that we do not
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* spin on a lock waiting for release. On error release all vnode locks
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* and decrement references the way tmpfs_rename() would do.
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*/
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static int
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tmpfs_rename_relock(struct vnode *fdvp, struct vnode **fvpp,
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struct vnode *tdvp, struct vnode **tvpp,
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struct componentname *fcnp, struct componentname *tcnp)
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{
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struct vnode *nvp;
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struct mount *mp;
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struct tmpfs_dirent *de;
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int error, restarts = 0;
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VOP_UNLOCK(tdvp, 0);
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if (*tvpp != NULL && *tvpp != tdvp)
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VOP_UNLOCK(*tvpp, 0);
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mp = fdvp->v_mount;
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relock:
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restarts += 1;
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error = vn_lock(fdvp, LK_EXCLUSIVE);
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if (error)
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goto releout;
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if (vn_lock(tdvp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
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VOP_UNLOCK(fdvp, 0);
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error = vn_lock(tdvp, LK_EXCLUSIVE);
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if (error)
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goto releout;
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VOP_UNLOCK(tdvp, 0);
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goto relock;
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}
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/*
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* Re-resolve fvp to be certain it still exists and fetch the
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* correct vnode.
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*/
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de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(fdvp), NULL, fcnp);
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if (de == NULL) {
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VOP_UNLOCK(fdvp, 0);
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VOP_UNLOCK(tdvp, 0);
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if ((fcnp->cn_flags & ISDOTDOT) != 0 ||
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(fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == '.'))
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error = EINVAL;
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else
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error = ENOENT;
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goto releout;
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}
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error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE | LK_NOWAIT, &nvp);
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if (error != 0) {
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VOP_UNLOCK(fdvp, 0);
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VOP_UNLOCK(tdvp, 0);
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if (error != EBUSY)
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goto releout;
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error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE, &nvp);
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if (error != 0)
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goto releout;
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VOP_UNLOCK(nvp, 0);
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/*
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* Concurrent rename race.
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*/
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if (nvp == tdvp) {
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vrele(nvp);
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error = EINVAL;
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goto releout;
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}
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vrele(*fvpp);
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*fvpp = nvp;
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goto relock;
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}
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vrele(*fvpp);
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*fvpp = nvp;
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VOP_UNLOCK(*fvpp, 0);
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/*
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* Re-resolve tvp and acquire the vnode lock if present.
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*/
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de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(tdvp), NULL, tcnp);
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/*
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* If tvp disappeared we just carry on.
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*/
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if (de == NULL && *tvpp != NULL) {
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vrele(*tvpp);
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*tvpp = NULL;
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}
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/*
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* Get the tvp ino if the lookup succeeded. We may have to restart
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* if the non-blocking acquire fails.
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*/
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if (de != NULL) {
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nvp = NULL;
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error = tmpfs_alloc_vp(mp, de->td_node,
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LK_EXCLUSIVE | LK_NOWAIT, &nvp);
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if (*tvpp != NULL)
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vrele(*tvpp);
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*tvpp = nvp;
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if (error != 0) {
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VOP_UNLOCK(fdvp, 0);
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VOP_UNLOCK(tdvp, 0);
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if (error != EBUSY)
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goto releout;
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error = tmpfs_alloc_vp(mp, de->td_node, LK_EXCLUSIVE,
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&nvp);
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if (error != 0)
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goto releout;
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VOP_UNLOCK(nvp, 0);
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/*
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* fdvp contains fvp, thus tvp (=fdvp) is not empty.
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*/
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if (nvp == fdvp) {
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error = ENOTEMPTY;
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goto releout;
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}
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goto relock;
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}
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}
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tmpfs_rename_restarts += restarts;
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return (0);
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releout:
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vrele(fdvp);
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vrele(*fvpp);
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vrele(tdvp);
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if (*tvpp != NULL)
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vrele(*tvpp);
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tmpfs_rename_restarts += restarts;
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return (error);
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}
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static int
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tmpfs_rename(struct vop_rename_args *v)
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{
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@ -927,6 +1068,7 @@ tmpfs_rename(struct vop_rename_args *v)
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struct vnode *tdvp = v->a_tdvp;
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struct vnode *tvp = v->a_tvp;
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struct componentname *tcnp = v->a_tcnp;
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struct mount *mp = NULL;
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char *newname;
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int error;
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@ -942,8 +1084,6 @@ tmpfs_rename(struct vop_rename_args *v)
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MPASS(fcnp->cn_flags & HASBUF);
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MPASS(tcnp->cn_flags & HASBUF);
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tnode = (tvp == NULL) ? NULL : VP_TO_TMPFS_NODE(tvp);
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/* Disallow cross-device renames.
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* XXX Why isn't this done by the caller? */
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if (fvp->v_mount != tdvp->v_mount ||
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@ -952,9 +1092,6 @@ tmpfs_rename(struct vop_rename_args *v)
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goto out;
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}
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tmp = VFS_TO_TMPFS(tdvp->v_mount);
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tdnode = VP_TO_TMPFS_DIR(tdvp);
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/* If source and target are the same file, there is nothing to do. */
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if (fvp == tvp) {
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error = 0;
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@ -963,8 +1100,37 @@ tmpfs_rename(struct vop_rename_args *v)
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/* If we need to move the directory between entries, lock the
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* source so that we can safely operate on it. */
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if (fdvp != tdvp && fdvp != tvp)
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vn_lock(fdvp, LK_EXCLUSIVE | LK_RETRY);
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if (fdvp != tdvp && fdvp != tvp) {
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if (vn_lock(fdvp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
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mp = tdvp->v_mount;
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error = vfs_busy(mp, 0);
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if (error != 0) {
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mp = NULL;
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goto out;
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}
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error = tmpfs_rename_relock(fdvp, &fvp, tdvp, &tvp,
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fcnp, tcnp);
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if (error != 0) {
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vfs_unbusy(mp);
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return (error);
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}
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ASSERT_VOP_ELOCKED(fdvp,
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"tmpfs_rename: fdvp not locked");
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ASSERT_VOP_ELOCKED(tdvp,
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"tmpfs_rename: tdvp not locked");
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if (tvp != NULL)
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ASSERT_VOP_ELOCKED(tvp,
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"tmpfs_rename: tvp not locked");
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if (fvp == tvp) {
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error = 0;
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goto out_locked;
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}
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}
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}
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tmp = VFS_TO_TMPFS(tdvp->v_mount);
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tdnode = VP_TO_TMPFS_DIR(tdvp);
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tnode = (tvp == NULL) ? NULL : VP_TO_TMPFS_NODE(tvp);
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fdnode = VP_TO_TMPFS_DIR(fdvp);
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fnode = VP_TO_TMPFS_NODE(fvp);
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de = tmpfs_dir_lookup(fdnode, fnode, fcnp);
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@ -1158,6 +1324,9 @@ tmpfs_rename(struct vop_rename_args *v)
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vrele(fdvp);
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vrele(fvp);
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if (mp != NULL)
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vfs_unbusy(mp);
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return error;
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}
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