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Differential D55028 Diff 170923 sys/fs/devfs/devfs_vnops.c

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sys/fs/devfs/devfs_vnops.c

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devfs_populate_vp(struct vnode *vp) devfs_populate_vp(struct vnode *vp)
{ {
struct devfs_dirent *de; struct devfs_dirent *de;
struct devfs_mount *dmp; struct devfs_mount *dmp;
int locked; int locked;
ASSERT_VOP_LOCKED(vp, "devfs_populate_vp"); ASSERT_VOP_LOCKED(vp, "devfs_populate_vp");
if (VN_IS_DOOMED(vp))
return (ENOENT);
dmp = VFSTODEVFS(vp->v_mount); dmp = VFSTODEVFS(vp->v_mount);
if (!devfs_populate_needed(dmp)) { if (!devfs_populate_needed(dmp)) {
sx_xlock(&dmp->dm_lock); sx_xlock(&dmp->dm_lock);
goto out_nopopulate; goto out_nopopulate;
} }
locked = VOP_ISLOCKED(vp); locked = VOP_ISLOCKED(vp);
▲ Show 20 Lines • Show All 745 Lines • ▼ Show 20 Lines while (de == NULL) { /* While(...) so we can use break */
*/ */
pname = devfs_fqpn(specname, dmp, dd, cnp); pname = devfs_fqpn(specname, dmp, dd, cnp);
if (pname == NULL) if (pname == NULL)
break; break;
cdev = NULL; cdev = NULL;
DEVFS_DMP_HOLD(dmp); DEVFS_DMP_HOLD(dmp);
sx_xunlock(&dmp->dm_lock); sx_xunlock(&dmp->dm_lock);
dvplocked = VOP_ISLOCKED(dvp);
/*
* Invoke the dev_clone handler. Unlock dvp around it
* to simplify the cloner operations.
*
* If dvp is reclaimed while we unlocked it, we return
* with ENOENT by some of the paths below. If cloner
* returned cdev, then devfs_populate_vp() notes the
* reclamation. Otherwise, note that either our devfs
* mount is being unmounted, then DEVFS_DMP_DROP()
* returns true, and we return ENOENT this way. Or,
* because de == NULL, the check for it after the loop
* returns ENOENT.
*/
VOP_UNLOCK(dvp);
EVENTHANDLER_INVOKE(dev_clone, EVENTHANDLER_INVOKE(dev_clone,
td->td_ucred, pname, strlen(pname), &cdev); td->td_ucred, pname, strlen(pname), &cdev);
vn_lock(dvp, dvplocked | LK_RETRY);
if (cdev == NULL) if (cdev == NULL)
sx_xlock(&dmp->dm_lock); sx_xlock(&dmp->dm_lock);
else if (devfs_populate_vp(dvp) != 0) { else if (devfs_populate_vp(dvp) != 0) {
markjUnsubmitted
Done
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Why is it correct to handle the DOOMED case after checking cdev == NULL? It's not immediately clear to me.

markj: Why is it correct to handle the DOOMED case after checking `cdev == NULL`? It's not immediately…
kibAuthorUnsubmitted
Done
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Why is it not? If cdev == NULL, we fall to some of the paths that end up with return (ENOENT);. Either the devfs instance is being unmounted, and then DEVFS_DMP_DROP() is true and we use the exit path starting at line 1153 (patched). Or we break out of the loop, and since de == NULL, we return ENOENT in line 1179.

kib: Why is it not? If cdev == NULL, we fall to some of the paths that end up with `return…
markjUnsubmitted
Not Done
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I see now, thanks. Specifically, I missed that we must fall into the de == NULL case if the case on line 1162 is hit.

markj: I see now, thanks. Specifically, I missed that we must fall into the de == NULL case if the…
*dm_unlock = 0; *dm_unlock = 0;
sx_xlock(&dmp->dm_lock); sx_xlock(&dmp->dm_lock);
if (DEVFS_DMP_DROP(dmp)) { if (DEVFS_DMP_DROP(dmp)) {
sx_xunlock(&dmp->dm_lock); sx_xunlock(&dmp->dm_lock);
devfs_unmount_final(dmp); devfs_unmount_final(dmp);
} else } else
sx_xunlock(&dmp->dm_lock); sx_xunlock(&dmp->dm_lock);
dev_rel(cdev); dev_rel(cdev);
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