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Added opt-in lazy sector release to reduce O(N²) deletion (issue #70) (#71)

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WARNING: This feature is brand new and has not been tested beyond the
existing regression suite.  It should be thoroughly tested — including
stress, power-loss, and wear-levelling scenarios — before being used in
any production system.

When LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE is defined and free blocks
exceed LX_NAND_FLASH_SECTOR_RELEASE_LAZY_THRESHOLD (default 10), releasing
a sector from a full block defers the copy+erase.  A tombstone page is
written to a freshly-allocated block; the old full block is flagged
COMPACTION_PENDING in its block status and recorded in a new per-LG
compaction table.  Compaction (merge + erase) is triggered lazily:

  * sector_write: before writing to a full block with a pending source
  * block_data_move: intercepts wear-levelling moves for pending LGs
  * defragment: iterates all pending LGs (now actually implemented)
  * block_allocate: emergency compaction when the free list is empty

Reads transparently fall back to the compaction-pending block when the
primary block does not contain the requested sector.

Crash recovery is handled in open_extended:
  - Phase 1: detects COMPACTION_PENDING blocks and either clears the flag
    (crash before mapping update — abort) or rebuilds compaction_table
    (crash after mapping update — resume deferred compaction).
  - Phase 2: erases orphaned ALLOCATED blocks not present in any mapping.

Without the flag, all paths remain unchanged and defragment returns
LX_NOT_SUPPORTED as before.

Fixes: https://github.com/eclipse-threadx/levelx/issues/70

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Frédéric Desbiens
2026-06-02 11:25:12 -04:00
committed by GitHub
co-authored by Copilot
parent a46b74fb8a
commit bfb39676df
11 changed files with 990 additions and 0 deletions
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common/src/lx_nand_flash_sector_read.c
+71
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@@ -9,6 +9,7 @@
* SPDX-License-Identifier: MIT
**************************************************************************/
// Some portions generated by Copilot (Sonnet 4.6).
/**************************************************************************/
/**************************************************************************/
@@ -231,6 +232,76 @@ LONG page;
}
}
#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
{
ULONG logical_group;
ULONG old_block;
/* Check the compaction table for a deferred source block that might hold
the requested sector. The primary block (tombstone block) was already
scanned above; fall back to the old full block here. */
logical_group = logical_sector / nand_flash -> lx_nand_flash_pages_per_block;
if (nand_flash -> lx_nand_flash_block_compaction_table[logical_group] != (USHORT)LX_NAND_BLOCK_UNMAPPED)
{
old_block = nand_flash -> lx_nand_flash_block_compaction_table[logical_group];
/* Set spare buffer pointer. */
spare_buffer_ptr = (UCHAR*)nand_flash -> lx_nand_flash_page_buffer;
/* The compaction-pending block is always FULL; scan all pages in reverse. */
for (page = (LONG)nand_flash -> lx_nand_flash_pages_per_block - 1; page >= 0; page--)
{
#ifdef LX_NAND_ENABLE_CONTROL_BLOCK_FOR_DRIVER_INTERFACE
status = (nand_flash -> lx_nand_flash_driver_pages_read)(nand_flash, old_block, (ULONG)page, (UCHAR*)NULL, spare_buffer_ptr, 1);
#else
status = (nand_flash -> lx_nand_flash_driver_pages_read)(old_block, (ULONG)page, (UCHAR*)NULL, spare_buffer_ptr, 1);
#endif
/* Check for an error from flash driver. */
if (status)
{
_lx_nand_flash_system_error(nand_flash, status, old_block, 0);
#ifdef LX_THREAD_SAFE_ENABLE
tx_mutex_put(&nand_flash -> lx_nand_flash_mutex);
#endif
return(LX_ERROR);
}
/* Check if this page matches the requested sector. */
if ((LX_UTILITY_LONG_GET(&spare_buffer_ptr[nand_flash -> lx_nand_flash_spare_data1_offset]) & LX_NAND_PAGE_TYPE_USER_DATA_MASK) == logical_sector)
{
#ifdef LX_NAND_ENABLE_CONTROL_BLOCK_FOR_DRIVER_INTERFACE
status = (nand_flash -> lx_nand_flash_driver_pages_read)(nand_flash, old_block, (ULONG)page, (UCHAR*)buffer, NULL, 1);
#else
status = (nand_flash -> lx_nand_flash_driver_pages_read)(old_block, (ULONG)page, (UCHAR*)buffer, NULL, 1);
#endif
/* Check for an error from flash driver. */
if (status)
{
_lx_nand_flash_system_error(nand_flash, status, old_block, 0);
#ifdef LX_THREAD_SAFE_ENABLE
tx_mutex_put(&nand_flash -> lx_nand_flash_mutex);
#endif
return(LX_ERROR);
}
#ifdef LX_THREAD_SAFE_ENABLE
tx_mutex_put(&nand_flash -> lx_nand_flash_mutex);
#endif
return(LX_SUCCESS);
}
}
}
}
#endif /* LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE */
/* Sector hasn't been written. Simply fill the destination buffer with ones and return success. */
/* Setup pointer to users buffer. */