ext4: fix races between page faults and hole punching

[firefly-linux-kernel-4.4.55.git] / fs / ext4 / extents.c

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 551353b1b17ab930ead8eff62ee3a699b4cfe10f..5be9ca5a8a7a204b6f4e63d7e6a7d2740157b174 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4770,7 +4770,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
        int partial_begin, partial_end;
        loff_t start, end;
        ext4_lblk_t lblk;
-       struct address_space *mapping = inode->i_mapping;
        unsigned int blkbits = inode->i_blkbits;
 
        trace_ext4_zero_range(inode, offset, len, mode);
@@ -4785,17 +4784,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
                        return ret;
        }
 
-       /*
-        * Write out all dirty pages to avoid race conditions
-        * Then release them.
-        */
-       if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
-               ret = filemap_write_and_wait_range(mapping, offset,
-                                                  offset + len - 1);
-               if (ret)
-                       return ret;
-       }
-
        /*
         * Round up offset. This is not fallocate, we neet to zero out
         * blocks, so convert interior block aligned part of the range to
@@ -4856,16 +4844,22 @@ static long ext4_zero_range(struct file *file, loff_t offset,
                flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
                          EXT4_EX_NOCACHE);
 
-               /* Now release the pages and zero block aligned part of pages*/
-               truncate_pagecache_range(inode, start, end - 1);
-               inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
-
                /* Wait all existing dio workers, newcomers will block on i_mutex */
                ext4_inode_block_unlocked_dio(inode);
                inode_dio_wait(inode);
 
+               /*
+                * Prevent page faults from reinstantiating pages we have
+                * released from page cache.
+                */
+               down_write(&EXT4_I(inode)->i_mmap_sem);
+               /* Now release the pages and zero block aligned part of pages */
+               truncate_pagecache_range(inode, start, end - 1);
+               inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
+
                ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
                                             flags, mode);
+               up_write(&EXT4_I(inode)->i_mmap_sem);
                if (ret)
                        goto out_dio;
        }
@@ -5524,17 +5518,22 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
                goto out_mutex;
        }
 
-       truncate_pagecache(inode, ioffset);
-
        /* Wait for existing dio to complete */
        ext4_inode_block_unlocked_dio(inode);
        inode_dio_wait(inode);
 
+       /*
+        * Prevent page faults from reinstantiating pages we have released from
+        * page cache.
+        */
+       down_write(&EXT4_I(inode)->i_mmap_sem);
+       truncate_pagecache(inode, ioffset);
+
        credits = ext4_writepage_trans_blocks(inode);
        handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
-               goto out_dio;
+               goto out_mmap;
        }
 
        down_write(&EXT4_I(inode)->i_data_sem);
@@ -5573,7 +5572,8 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 
 out_stop:
        ext4_journal_stop(handle);
-out_dio:
+out_mmap:
+       up_write(&EXT4_I(inode)->i_mmap_sem);
        ext4_inode_resume_unlocked_dio(inode);
 out_mutex:
        mutex_unlock(&inode->i_mutex);
@@ -5660,17 +5660,22 @@ int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
                goto out_mutex;
        }
 
-       truncate_pagecache(inode, ioffset);
-
        /* Wait for existing dio to complete */
        ext4_inode_block_unlocked_dio(inode);
        inode_dio_wait(inode);
 
+       /*
+        * Prevent page faults from reinstantiating pages we have released from
+        * page cache.
+        */
+       down_write(&EXT4_I(inode)->i_mmap_sem);
+       truncate_pagecache(inode, ioffset);
+
        credits = ext4_writepage_trans_blocks(inode);
        handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
-               goto out_dio;
+               goto out_mmap;
        }
 
        /* Expand file to avoid data loss if there is error while shifting */
@@ -5741,7 +5746,8 @@ int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
 
 out_stop:
        ext4_journal_stop(handle);
-out_dio:
+out_mmap:
+       up_write(&EXT4_I(inode)->i_mmap_sem);
        ext4_inode_resume_unlocked_dio(inode);
 out_mutex:
        mutex_unlock(&inode->i_mutex);