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Gary Guo
1644e2ffd2
When copy_file_range overwrites a recent truncation, subsequent reads can incorrectly determine that it is read hole instead of reading the cloned blocks. This can happen when the following conditions are met: - Truncate adds blkid to dn_free_ranges - A new TXG is created - copy_file_range calls dmu_brt_clone which override the block pointer and set DB_NOFILL - Subsequent read, given DB_NOFILL, hits dbuf_read_impl and dbuf_read_hole - dbuf_read_hole calls dnode_block_freed, which returns TRUE because the truncated blkids are still in dn_free_ranges This will not happen if the clone and truncate are in the same TXG, because the block clone would update the current TXG's dn_free_ranges, which is why this bug only triggers under high IO load (such as compilation). Fix this by skipping the dnode_block_freed call if the block is overridden. The fix shouldn't cause an issue when the cloned block is subsequently freed in later TXGs, as dbuf_undirty would remove the override. This requires a dedicated test program as it is much harder to trigger with scripts (this needs to generate a lot of I/O in short period of time for the bug to trigger reliably). Assisted-by: Gemini:gemini-3.1-pro Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Signed-off-by: Gary Guo <[email protected]> Closes #18412 Closes #18421