ext4: fix ZERO_RANGE bug hidden by flag aliasing (713e8dde) · Commits · 戴 / test

We accidently aliased EXT4_EX_NOCACHE and EXT4_GET_CONVERT_UNWRITTEN falgs, which apparently was hiding a bug that was unmasked when this flag aliasing issue was addressed (see the subsequent commit). The reproduction case was: fsx -N 10000 -l 500000 -r 4096 -t 4096 -w 4096 -Z -R -W /vdb/junk ... which would cause fsx to report corruption in the data file. The fix we have is a bit of an overkill, but I'd much rather be conservative for now, and we can optimize ZERO_RANGE_FL handling later. The fact that we need to zap the extent_status cache for the inode is unfortunate, but correctness is far more important than performance. Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Cc: Namjae Jeon <namjae.jeon@samsung.com>

fs/ext4/extents.c

+14 −7

Original line number	Diff line number	Diff line
		@@ -4802,7 +4802,8 @@ static long ext4_zero_range(struct file *file, loff_t offset,
		max_blocks -= lblk;

		flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT \|
		EXT4_GET_BLOCKS_CONVERT_UNWRITTEN;
		EXT4_GET_BLOCKS_CONVERT_UNWRITTEN \|
		EXT4_EX_NOCACHE;
		if (mode & FALLOC_FL_KEEP_SIZE)
		flags \|= EXT4_GET_BLOCKS_KEEP_SIZE;

		@@ -4840,17 +4841,23 @@ static long ext4_zero_range(struct file *file, loff_t offset,
		ext4_inode_block_unlocked_dio(inode);
		inode_dio_wait(inode);

		/*
		* Remove entire range from the extent status tree.
		*/
		ret = ext4_es_remove_extent(inode, lblk, max_blocks);
		if (ret)
		goto out_dio;

		ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
		flags, mode);
		if (ret)
		goto out_dio;
		/*
		* Remove entire range from the extent status tree.
		*
		* ext4_es_remove_extent(inode, lblk, max_blocks) is
		* NOT sufficient. I'm not sure why this is the case,
		* but let's be conservative and remove the extent
		* status tree for the entire inode. There should be
		* no outstanding delalloc extents thanks to the
		* filemap_write_and_wait_range() call above.
		*/
		ret = ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);
		if (ret)
		goto out_dio;
		}
		if (!partial_begin && !partial_end)
		goto out_dio;

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