Messages in this thread Patch in this message | | | Date | Thu, 10 Jan 2002 00:42:08 +0000 (GMT) | From | Hugh Dickins <> | Subject | [PATCH] pagecache lock ordering |
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There's two places, do_buffer_fdatasync and __find_lock_page_helper, which violate the pagemap_lru_lock before pagecache_lock rule, if page_cache_release frees page calling lru_cache_del.
I was worried when I saw Ben's patch to move lru_cache_del down into __free_pages_ok: thought it might cause a spinlock ordering violation somewhere. Source check showed up no new problem from his patch, but these two already a problem (and still a problem when Ben's patch goes in).
Hugh
--- 2.4.18-pre2/mm/filemap.c Wed Jan 9 18:17:39 2002 +++ linux/mm/filemap.c Wed Jan 9 19:11:17 2002 @@ -493,6 +493,7 @@ { struct list_head *curr; struct page *page; + struct page *relpage = NULL; int retval = 0; spin_lock(&pagecache_lock); @@ -509,6 +510,9 @@ page_cache_get(page); spin_unlock(&pagecache_lock); + if (relpage) + page_cache_release(relpage); + relpage = page; lock_page(page); /* The buffers could have been free'd while we waited for the page lock */ @@ -518,10 +522,11 @@ UnlockPage(page); spin_lock(&pagecache_lock); curr = page->list.next; - page_cache_release(page); } spin_unlock(&pagecache_lock); + if (relpage) + page_cache_release(relpage); return retval; } @@ -900,14 +905,15 @@ if (TryLockPage(page)) { spin_unlock(&pagecache_lock); lock_page(page); - spin_lock(&pagecache_lock); /* Has the page been re-allocated while we slept? */ if (page->mapping != mapping || page->index != offset) { UnlockPage(page); page_cache_release(page); + spin_lock(&pagecache_lock); goto repeat; } + spin_lock(&pagecache_lock); } } return page; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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