At one point DAX used i_mmap_lock so synchronize page faults with page
table invalidation during truncate. However these days DAX uses
filesystem specific RW semaphores to protect against these races
(i_mmap_sem in ext2 & ext4 cases, XFS_MMAPLOCK in xfs case). So remove
the unnecessary locking.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/dax.c | 19 -------------------
mm/memory.c | 14 --------------
2 files changed, 33 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 9c4d697fb6fc..e409e8fc13b7 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -563,8 +563,6 @@ 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
@@ -597,8 +595,6 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
error = vm_insert_mixed(vma, vaddr, dax.pfn);
out:
- i_mmap_unlock_read(mapping);
-
return error;
}
@@ -695,17 +691,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
if (error)
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 out;
- }
- }
return VM_FAULT_LOCKED;
}
@@ -895,8 +880,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
truncate_pagecache_range(inode, lstart, lend);
}
- i_mmap_lock_read(mapping);
-
/*
* If a truncate happened while we were allocating blocks, we may
* leave blocks allocated to the file that are beyond EOF. We can't
@@ -1013,8 +996,6 @@ 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));
diff --git a/mm/memory.c b/mm/memory.c
index 8132787ae4d5..13f76eb08f33 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2430,8 +2430,6 @@ void unmap_mapping_range(struct address_space *mapping,
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
-
- /* 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);
@@ -3019,12 +3017,6 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (fault_page) {
unlock_page(fault_page);
page_cache_release(fault_page);
- } else {
- /*
- * The fault handler has no page to lock, so it holds
- * i_mmap_lock for read to protect against truncate.
- */
- i_mmap_unlock_read(vma->vm_file->f_mapping);
}
goto uncharge_out;
}
@@ -3035,12 +3027,6 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (fault_page) {
unlock_page(fault_page);
page_cache_release(fault_page);
- } else {
- /*
- * The fault handler has no page to lock, so it holds
- * i_mmap_lock for read to protect against truncate.
- */
- i_mmap_unlock_read(vma->vm_file->f_mapping);
}
return ret;
uncharge_out:
--
2.6.2
--
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