xfs: delayed alloc blocks beyond EOF are valid after writeback
There is an assumption in the parts of XFS that flushing a dirty file will make all the delayed allocation blocks disappear from an inode. That is, that after calling xfs_flush_pages() then ip->i_delayed_blks will be zero. This is an invalid assumption as we may have specualtive preallocation beyond EOF and they are recorded in ip->i_delayed_blks. A flush of the dirty pages of an inode will not change the state of these blocks beyond EOF, so a non-zero deeelalloc block count after a flush is valid. The bmap code has an invalid ASSERT() that needs to be removed, and the swapext code has a bug in that while it swaps the data forks around, it fails to swap the i_delayed_blks counter associated with the fork and hence can get the block accounting wrong. Signed-off-by: NDave Chinner <dchinner@redhat.com> Reviewed-by: NChristoph Hellwig <hch@lst.de>
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