Re: [PATCH v1] fsck.erofs: implement thread-safe global LRU metadata cache

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2026/6/11 16:36, Nithurshen wrote:
> This patch introduces a thread-safe metadata cache to reduce redundant
> I/O and decompression overhead during fsck extraction.
> 
> To ensure it remains highly concurrent for worker threads extracting
> pclusters, the cache utilizes a bucketed, rw-semaphore protected
> architecture modeled after the existing fragment cache.
> 
> Furthermore, to prevent out-of-memory (OOM) scenarios on exceptionally
> large EROFS images, the cache implements a strict Global Least Recently
> Used (LRU) eviction policy. The maximum cache size is dynamically
> configurable via the new '--cache-size' parameter, which defaults to a
> safe, fixed threshold of 32 MB.
> 
> Signed-off-by: Nithurshen <nithurshen.dev@gmail.com>

why `malloc()` will prevent out-of-memory (OOM)?

First, either erofs_read_metadata_nid() or erofs_read_metadata_bdi()
will read file to the page cache; and currently there is no cache.


But you introduce another cache using malloc(), since it increases
the memory overhead, why it prevents out-of-memory (OOM)?

Thanks,
Gao Xiang