MFC r328957:
{ext2|ufs}_readdir: Avoid setting negative ncookies.

ncookies cannot be negative or the allocator will fail. This should only
happen if a caller is very broken but we can still try to survive the
event.

We should probably also verify for uio_resid > MAXPHYS but in that case
it is not clear that just clipping the ncookies value is an adequate
response.

MFC r307978:
Bug 180894 reports that rm -rf on a directory causes kernel panic and reboot.
Return EINVAL rather than panic for low directory link count.

PR: 180894

MFC r305601:
On rename, do not perform truncation of dirhash if the vnode truncation failed.

MFC r303090:
Ensure that the UFS directory vnode' vm_object is properly sized
before UFS_BALLOC() is called.

MFC r300142:
Ensure that ftruncate(2) is performed synchronously when file is
opened in O_SYNC mode, at least for UFS.

MFC r291936:
Update ctime when atime or birthtime are updated.
Cleanup setting of ctime/mtime/birthtime.

MFC r276007:
Handle MAKEENTRY cnp flag in the VOP_CREATE().

MFC r270204:
Do not busy the UFS mount point inside VOP_RENAME().

MFC r268764:
Check for the cross-device cross-link attempt in the VFS, instead of
VOP_LINK() implemenations.

MFC r267564:
In msdosfs_setattr(), add a check for result of the utimes(2) permissions test.
Refactor the permission checks for utimes(2).

MFC r276007:
Handle MAKEENTRY cnp flag in the VOP_CREATE().

MFC r270204:
Do not busy the UFS mount point inside VOP_RENAME().

MFC r268764:
Check for the cross-device cross-link attempt in the VFS, instead of
VOP_LINK() implemenations.

MFC r267564:
In msdosfs_setattr(), add a check for result of the utimes(2) permissions test.
Refactor the permission checks for utimes(2).