MDEV-37924 segv in flst::remove_complete(buf_block_t*, unsigned short, unsigned char*, mtr_t*)#4896
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Thirunarayanan wants to merge 1 commit into11.4from
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MDEV-37924 segv in flst::remove_complete(buf_block_t*, unsigned short, unsigned char*, mtr_t*)#4896Thirunarayanan wants to merge 1 commit into11.4from
Thirunarayanan wants to merge 1 commit into11.4from
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…, unsigned char*, mtr_t*) Problem: ======= During system tablespace defragmentation, extent movement occurs in two phases: prepare and complete. 1) prepare phase validates involved pages and acquires necessary resources. 2) complete phase performs the actual data copy. Prepare phase fails to check whether allocating a page will make the extent FULL. When an extent has exactly (extent_size - 1) pages used, the prepare phase returns early without latching the prev/next extent descriptors needed for list manipulation. Complete phase then allocates the final page, making the extent full, and attempts to move it from FSEG_NOT_FULL/FSP_FREE_FRAG to FSEG_FULL/FSP_FULL_FRAG list. This fails with an assertion because the required blocks were never latched, causing a crash in flst::remove_complete(). Solution: ======== alloc_from_fseg_prepare(), alloc_from_free_frag_prepare(): Check if the extent will become full after allocation. This makes the prepare phase to acquire the necessary pages for FSP list manipulation find_new_extents(): Print more revised information about moving of extent data and destination extent also. defragment_level(): Move get_child_pages(new_block) before committing changes to enable proper rollback on failure. Well, this failure is theoretically impossible (new block is exact copy of validated old block).
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Problem:
During system tablespace defragmentation, extent movement occurs in two phases: prepare and complete.
Prepare phase fails to check whether allocating a page will make the extent FULL. When an extent has exactly (extent_size - 1) pages used, the prepare phase returns early without latching the prev/next extent descriptors needed for list manipulation.
Complete phase then allocates the final page, making the extent full, and attempts to move it from
FSEG_NOT_FULL/FSP_FREE_FRAG to FSEG_FULL/FSP_FULL_FRAG list. This fails with an assertion because the required blocks were never latched, causing a crash in flst::remove_complete().
Solution:
alloc_from_fseg_prepare(), alloc_from_free_frag_prepare(): Check if the extent will become full after allocation. This makes the prepare phase to acquire the necessary pages for FSP list manipulation
find_new_extents(): Print more revised information about moving of extent data and destination extent also.
defragment_level(): Move get_child_pages(new_block) before committing changes to enable proper rollback on failure. Well, this failure is theoretically impossible (new block is exact copy of validated old block).