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Subject[PATCH 3/7] mm: drop the mmap_sem in all read fault cases
Date
Johannes' patches didn't quite cover all of the IO cases that we need to
drop the mmap_sem for, this patch covers the rest of them.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
mm/filemap.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 1ed35cd99b2c..65395ee132a0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2523,6 +2523,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
int error;
struct mm_struct *mm = vmf->vma->vm_mm;
struct file *file = vmf->vma->vm_file;
+ struct file *fpin = NULL;
struct address_space *mapping = file->f_mapping;
struct file_ra_state *ra = &file->f_ra;
struct inode *inode = mapping->host;
@@ -2610,11 +2611,15 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
return ret | VM_FAULT_LOCKED;

no_cached_page:
+ fpin = maybe_unlock_mmap_for_io(vmf->vma, vmf->flags);
+
/*
* We're only likely to ever get here if MADV_RANDOM is in
* effect.
*/
error = page_cache_read(file, offset, vmf->gfp_mask);
+ if (fpin)
+ goto out_retry;

/*
* The page we want has now been added to the page cache.
@@ -2634,6 +2639,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
return VM_FAULT_SIGBUS;

page_not_uptodate:
+ fpin = maybe_unlock_mmap_for_io(vmf->vma, vmf->flags);
+
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
@@ -2647,6 +2654,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
if (!PageUptodate(page))
error = -EIO;
}
+ if (fpin)
+ goto out_retry;
put_page(page);

if (!error || error == AOP_TRUNCATED_PAGE)
@@ -2665,6 +2674,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
}

out_retry:
+ if (fpin)
+ fput(fpin);
if (page)
put_page(page);
return ret | VM_FAULT_RETRY;
--
2.14.3
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