ext4: move unlocked dio protection from ext4_alloc_file_blocks()

Orabug: 23331010

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>
Reviewed-by: Mingming Cao <mingming.cao@oracle.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 9621787d69783fc23d14e1332377d7170d6928ed)

Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 96835e7fa71516d966c533dc7115bf13d6afffa8..fee4844a58e9e1cb53c7b32214cf0423616a5135 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4798,6 +4798,10 @@ 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,
@@ -4806,7 +4810,7 @@ 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;
 
        }
 
@@ -4815,10 +4819,6 @@ 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.
@@ -4958,8 +4958,13 @@ 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;