UPSTREAM: mm: handle read faults under the VMA lock

Most file-backed faults are already handled through ->map_pages(), but if
we need to do I/O we'll come this way.  Since filemap_fault() is now safe
to be called under the VMA lock, we can handle these faults under the VMA
lock now.

Link: https://lkml.kernel.org/r/20231006195318.4087158-6-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 12214eba)

Bug: 293665307
Change-Id: Iee48af98b866d88d88ec01143eb26389ab373b6b
Signed-off-by: Suren Baghdasaryan <surenb@google.com>