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Message-Id: <1443685599-4843-3-git-send-email-david@fromorbit.com>
Date: Thu, 1 Oct 2015 17:46:34 +1000
From: Dave Chinner <david@...morbit.com>
To: xfs@....sgi.com
Cc: linux-fsdevel@...r.kernel.org, ross.zwisler@...ux.intel.com,
willy@...ux.intel.com, dan.j.williams@...el.com,
kirill.shutemov@...ux.intel.com, linux-nvdimm@...ts.01.org,
jack@...e.cz, linux-kernel@...r.kernel.org
Subject: [PATCH 2/7] Revert "dax: fix race between simultaneous faults"
This reverts commit 843172978bb92997310d2f7fbc172ece423cfc02.
---
fs/dax.c | 33 ++++++++++++++++-----------------
mm/memory.c | 11 +++--------
2 files changed, 19 insertions(+), 25 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 400fe95..3994a2b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -285,6 +285,7 @@ static int copy_user_bh(struct page *to, struct buffer_head *bh,
static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
+ struct address_space *mapping = inode->i_mapping;
sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
unsigned long vaddr = (unsigned long)vmf->virtual_address;
void __pmem *addr;
@@ -292,6 +293,8 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
pgoff_t size;
int error;
+ i_mmap_lock_read(mapping);
+
/*
* Check truncate didn't happen while we were allocating a block.
* If it did, this block may or may not be still allocated to the
@@ -321,6 +324,8 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
error = vm_insert_mixed(vma, vaddr, pfn);
out:
+ i_mmap_unlock_read(mapping);
+
return error;
}
@@ -382,17 +387,15 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
* from a read fault and we've raced with a truncate
*/
error = -EIO;
- goto unlock;
+ goto unlock_page;
}
- } else {
- i_mmap_lock_write(mapping);
}
error = get_block(inode, block, &bh, 0);
if (!error && (bh.b_size < PAGE_SIZE))
error = -EIO; /* fs corruption? */
if (error)
- goto unlock;
+ goto unlock_page;
if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
if (vmf->flags & FAULT_FLAG_WRITE) {
@@ -403,9 +406,8 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
if (!error && (bh.b_size < PAGE_SIZE))
error = -EIO;
if (error)
- goto unlock;
+ goto unlock_page;
} else {
- i_mmap_unlock_write(mapping);
return dax_load_hole(mapping, page, vmf);
}
}
@@ -417,15 +419,17 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
else
clear_user_highpage(new_page, vaddr);
if (error)
- goto unlock;
+ goto unlock_page;
vmf->page = page;
if (!page) {
+ i_mmap_lock_read(mapping);
/* Check we didn't race with truncate */
size = (i_size_read(inode) + PAGE_SIZE - 1) >>
PAGE_SHIFT;
if (vmf->pgoff >= size) {
+ i_mmap_unlock_read(mapping);
error = -EIO;
- goto unlock;
+ goto out;
}
}
return VM_FAULT_LOCKED;
@@ -461,8 +465,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
}
- if (!page)
- i_mmap_unlock_write(mapping);
out:
if (error == -ENOMEM)
return VM_FAULT_OOM | major;
@@ -471,14 +473,11 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
return VM_FAULT_SIGBUS | major;
return VM_FAULT_NOPAGE | major;
- unlock:
+ unlock_page:
if (page) {
unlock_page(page);
page_cache_release(page);
- } else {
- i_mmap_unlock_write(mapping);
}
-
goto out;
}
EXPORT_SYMBOL(__dax_fault);
@@ -556,10 +555,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
bh.b_size = PMD_SIZE;
- i_mmap_lock_write(mapping);
length = get_block(inode, block, &bh, write);
if (length)
return VM_FAULT_SIGBUS;
+ i_mmap_lock_read(mapping);
/*
* If the filesystem isn't willing to tell us the length of a hole,
@@ -633,11 +632,11 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
}
out:
+ i_mmap_unlock_read(mapping);
+
if (buffer_unwritten(&bh))
complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
- i_mmap_unlock_write(mapping);
-
return result;
fallback:
diff --git a/mm/memory.c b/mm/memory.c
index 5ec066f..deb679c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2427,16 +2427,11 @@ void unmap_mapping_range(struct address_space *mapping,
details.last_index = ULONG_MAX;
- /*
- * DAX already holds i_mmap_lock to serialise file truncate vs
- * page fault and page fault vs page fault.
- */
- if (!IS_DAX(mapping->host))
- i_mmap_lock_write(mapping);
+ /* DAX uses i_mmap_lock to serialise file truncate vs page fault */
+ i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
- if (!IS_DAX(mapping->host))
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_write(mapping);
}
EXPORT_SYMBOL(unmap_mapping_range);
--
2.5.0
--
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