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MDEV-30753 fixup: Unsafe buffer page restoration

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trx_purge_free_segment(): The buffer-fix only prevents a block from
being freed completely from the buffer pool, but it will not prevent
the block from being evicted. Recheck the page identifier after
acquiring an exclusive page latch. If it has changed, backtrack and
invoke buf_page_get_gen() to look up the page normally.
This commit is contained in:
Marko Mäkelä 2023-04-21 11:05:44 +03:00
parent 210db2935c
commit c6e58a8d17
1 changed files with 13 additions and 2 deletions
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15
storage/innobase/trx/trx0purge.cc
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@ -367,19 +367,30 @@ void trx_purge_free_segment(mtr_t &mtr, trx_rseg_t* rseg, fil_addr_t hdr_addr)
block->frame, &mtr))
{
block->fix();
const page_id_t id{block->page.id()};
mtr.commit();
/* NOTE: If the server is killed after the log that was produced
up to this point was written, and before the log from the mtr.commit()
in our caller is written, then the pages belonging to the
undo log will become unaccessible garbage.
This does not matters when using multiple innodb_undo_tablespaces;
This does not matter when using multiple innodb_undo_tablespaces;
innodb_undo_log_truncate=ON will be able to reclaim the space. */
log_free_check();
mtr.start();
ut_ad(rw_lock_s_lock_nowait(block->debug_latch, __FILE__, __LINE__));
rw_lock_x_lock(&block->lock);
mtr_memo_push(&mtr, block, MTR_MEMO_PAGE_X_FIX);
if (UNIV_UNLIKELY(block->page.id() != id))
{
block->unfix();
rw_lock_x_unlock(&block->lock);
ut_d(rw_lock_s_unlock(block->debug_latch));
block= buf_page_get(id, 0, RW_X_LATCH, &mtr);
if (!block)
return;
}
else
mtr_memo_push(&mtr, block, MTR_MEMO_PAGE_X_FIX);
}
while (!fseg_free_step(TRX_UNDO_SEG_HDR + TRX_UNDO_FSEG_HEADER +