Commit 1a31182e authored Sep 28, 2020 by Goldwyn Rodrigues Committed by Darrick J. Wong Sep 28, 2020

iomap: Call inode_dio_end() before generic_write_sync()



iomap complete routine can deadlock with btrfs_fallocate because of the
call to generic_write_sync().

P0                      P1
inode_lock()            fallocate(FALLOC_FL_ZERO_RANGE)
__iomap_dio_rw()        inode_lock()
                        <block>
<submits IO>
<completes IO>
inode_unlock()
                        <gets inode_lock()>
                        inode_dio_wait()
iomap_dio_complete()
  generic_write_sync()
    btrfs_file_fsync()
      inode_lock()
      <deadlock>

inode_dio_end() is used to notify the end of DIO data in order
to synchronize with truncate. Call inode_dio_end() before calling
generic_write_sync(), so filesystems can lock i_rwsem during a sync.

This matches the way it is done in fs/direct-io.c:dio_complete().

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

parent c3d4ed1a

fs/iomap/direct-io.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -118,6 +118,7 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
		dio_warn_stale_pagecache(iocb->ki_filp);
		}

		inode_dio_end(file_inode(iocb->ki_filp));
		/*
		* If this is a DSYNC write, make sure we push it to stable storage now
		* that we've written data.
		@@ -125,7 +126,6 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
		if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
		ret = generic_write_sync(iocb, ret);

		inode_dio_end(file_inode(iocb->ki_filp));
		kfree(dio);

		return ret;

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