ext4: move unlocked dio protection from ext4_alloc_file_blocks()

commit 17048e8a083fec7ad841d88ef0812707fbc7e39f upstream.

Currently ext4_alloc_file_blocks() was handling protection against
unlocked DIO. However we now need to sometimes call it under i_mmap_sem
and sometimes not and DIO protection ranks above it (although strictly
speaking this cannot currently create any deadlocks). Also
ext4_zero_range() was actually getting & releasing unlocked DIO
protection twice in some cases. Luckily it didn't introduce any real bug
but it was a land mine waiting to be stepped on.  So move DIO protection
out from ext4_alloc_file_blocks() into the two callsites.

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 9c7d5d6fdc98d20d40cec3a945e9efe9e5402802..fb722d250537aeeca15c4d3185e2ec7ff33cb32c 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4707,10 +4707,6 @@ static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
        if (len <= EXT_UNWRITTEN_MAX_LEN)
                flags |= EXT4_GET_BLOCKS_NO_NORMALIZE;
 
-       /* Wait all existing dio workers, newcomers will block on i_mutex */
-       ext4_inode_block_unlocked_dio(inode);
-       inode_dio_wait(inode);
-
        /*
         * credits to insert 1 extent into extent tree
         */
@@ -4760,8 +4756,6 @@ retry:
                goto retry;
        }
 
-       ext4_inode_resume_unlocked_dio(inode);
-
        return ret > 0 ? ret2 : ret;
 }
 
@@ -4836,6 +4830,10 @@ static long ext4_zero_range(struct file *file, loff_t offset,
        if (mode & FALLOC_FL_KEEP_SIZE)
                flags |= EXT4_GET_BLOCKS_KEEP_SIZE;
 
+       /* Wait all existing dio workers, newcomers will block on i_mutex */
+       ext4_inode_block_unlocked_dio(inode);
+       inode_dio_wait(inode);
+
        /* Preallocate the range including the unaligned edges */
        if (partial_begin || partial_end) {
                ret = ext4_alloc_file_blocks(file,
@@ -4844,7 +4842,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
                                 round_down(offset, 1 << blkbits)) >> blkbits,
                                new_size, flags, mode);
                if (ret)
-                       goto out_mutex;
+                       goto out_dio;
 
        }
 
@@ -4853,10 +4851,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
                flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
                          EXT4_EX_NOCACHE);
 
-               /* 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.
@@ -4985,8 +4979,13 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
                        goto out;
        }
 
+       /* Wait all existing dio workers, newcomers will block on i_mutex */
+       ext4_inode_block_unlocked_dio(inode);
+       inode_dio_wait(inode);
+
        ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
                                     flags, mode);
+       ext4_inode_resume_unlocked_dio(inode);
        if (ret)
                goto out;