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FROMGIT: mm: run the fault-around code under the VMA lock

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The map_pages fs method should be safe to run under the VMA lock instead
of the mmap lock.  This should have a measurable reduction in contention
on the mmap lock.

Link: https://lkml.kernel.org/r/20230724185410.1124082-9-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit 7456c15600264d635293c91df1e0c0b5a1e73578
https: //git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)

Bug: 293665307
Change-Id: Iaa1b0c2deeade361b34118f41b5deb591268a269
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-07-24 19:54:08 +01:00 committed by Suren Baghdasaryan
parent 072c35fb69
commit ffcebdef16
1 changed files with 5 additions and 5 deletions
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10
mm/memory.c
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@ -4585,11 +4585,6 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
{
vm_fault_t ret = 0;
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
vma_end_read(vmf->vma);
return VM_FAULT_RETRY;
}
/*
* Let's call ->map_pages() first and use ->fault() as fallback
* if page by the offset is not ready to be mapped (cold cache or
@ -4601,6 +4596,11 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
return ret;
}
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
vma_end_read(vmf->vma);
return VM_FAULT_RETRY;
}
ret = __do_fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;