dax: Remove i_mmap_lock protection

Currently faults are protected against truncate by filesystem specific
i_mmap_sem and page lock in case of hole page. Cow faults are protected
DAX radix tree entry locking. So there's no need for i_mmap_lock in DAX
code. Remove it.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

diff --git a/fs/dax.c b/fs/dax.c
index be74635..6dbe602 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -798,29 +798,19 @@ static int dax_insert_mapping(struct address_space *mapping,
                .sector = to_sector(bh, mapping->host),
                .size = bh->b_size,
        };
-       int error;
        void *ret;
        void *entry = *entryp;
 
-       i_mmap_lock_read(mapping);
-
-       if (dax_map_atomic(bdev, &dax) < 0) {
-               error = PTR_ERR(dax.addr);
-               goto out;
-       }
+       if (dax_map_atomic(bdev, &dax) < 0)
+               return PTR_ERR(dax.addr);
        dax_unmap_atomic(bdev, &dax);
 
        ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
-       if (IS_ERR(ret)) {
-               error = PTR_ERR(ret);
-               goto out;
-       }
+       if (IS_ERR(ret))
+               return PTR_ERR(ret);
        *entryp = ret;
 
-       error = vm_insert_mixed(vma, vaddr, dax.pfn);
- out:
-       i_mmap_unlock_read(mapping);
-       return error;
+       return vm_insert_mixed(vma, vaddr, dax.pfn);
 }
 
 /**
@@ -1058,8 +1048,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                truncate_pagecache_range(inode, lstart, lend);
        }
 
-       i_mmap_lock_read(mapping);
-
        if (!write && !buffer_mapped(&bh)) {
                spinlock_t *ptl;
                pmd_t entry;
@@ -1148,8 +1136,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
        }
 
  out:
-       i_mmap_unlock_read(mapping);
-
        return result;
 
  fallback:

diff --git a/mm/memory.c b/mm/memory.c
index f09cdb8..06f5525 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2453,8 +2453,6 @@ 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);