-
Omar Sandoval authored
Commit 4f579ae7 (ext4: fix punch hole on files with indirect mapping) rewrote FALLOC_FL_PUNCH_HOLE for ext4 files with indirect mapping. However, there are bugs in several corner cases. This fixes 5 distinct bugs: 1. When there is at least one entire level of indirection between the start and end of the punch range and the end of the punch range is the first block of its level, we can't return early; we have to free the intervening levels. 2. When the end is at a higher level of indirection than the start and ext4_find_shared returns a top branch for the end, we still need to free the rest of the shared branch it returns; we can't decrement partial2. 3. When a punch happens within one level of indirection, we need to converge on an indirect block that contains the start and end. However, because the branches returned from ext4_find_shared do not necessarily start at the same level (e.g., the partial2 chain will be shallower if the last block occurs at the beginning of an indirect group), the walk of the two chains can end up "missing" each other and freeing a bunch of extra blocks in the process. This mismatch can be handled by first making sure that the chains are at the same level, then walking them together until they converge. 4. When the punch happens within one level of indirection and ext4_find_shared returns a top branch for the start, we must free it, but only if the end does not occur within that branch. 5. When the punch happens within one level of indirection and ext4_find_shared returns a top branch for the end, then we shouldn't free the block referenced by the end of the returned chain (this mirrors the different levels case). Signed-off-by: Omar Sandoval <osandov@osandov.com>
6f30b7e3