Commit 17048e8a authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: move unlocked dio protection from ext4_alloc_file_blocks() 



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: default avatarJan Kara <jack@suse.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent ea3d7209

fs/ext4/extents.c

+10 −11
Original line number Diff line number Diff line
@@ -4685,10 +4685,6 @@ 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

	 */
@@ -4752,8 +4748,6 @@ retry: 
		goto retry;

	}



	ext4_inode_resume_unlocked_dio(inode);



	return ret > 0 ? ret2 : ret;

}
@@ -4827,6 +4821,10 @@ 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,
@@ -4835,7 +4833,7 @@ 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;



	}
@@ -4844,10 +4842,6 @@ 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.
@@ -4992,8 +4986,13 @@ 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;

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