ext4: Fix sub-block zeroing for writes into preallocated extents (9c1ee184) · Commits · 戴 / test

We need to mark the buffer_head mapping preallocated space as new during write_begin. Otherwise we don't zero out the page cache content properly for a partial write. This will cause file corruption with preallocation. Now that we mark the buffer_head new we also need to have a valid buffer_head blocknr so that unmap_underlying_metadata() unmaps the correct block. Signed-off-by:

Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/extents.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2875,6 +2875,8 @@ int ext4_ext_get_blocks(handle_t handle, struct inode inode,
		if (allocated > max_blocks)
		allocated = max_blocks;
		set_buffer_unwritten(bh_result);
		bh_result->b_bdev = inode->i_sb->s_bdev;
		bh_result->b_blocknr = newblock;
		goto out2;
		}

fs/ext4/inode.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -2323,6 +2323,13 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
		set_buffer_delay(bh_result);
		} else if (ret > 0) {
		bh_result->b_size = (ret << inode->i_blkbits);
		/*
		* With sub-block writes into unwritten extents
		* we also need to mark the buffer as new so that
		* the unwritten parts of the buffer gets correctly zeroed.
		*/
		if (buffer_unwritten(bh_result))
		set_buffer_new(bh_result);
		ret = 0;
		}

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