From 61b4c050ad5dcb1c8dfa58e1f183f512e43055ea Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 4 Apr 2018 13:41:26 +0100 Subject: [PATCH] fscache: Fix hanging wait on page discarded by writeback [ Upstream commit 2c98425720233ae3e135add0c7e869b32913502f ] If the fscache asynchronous write operation elects to discard a page that's pending storage to the cache because the page would be over the store limit then it needs to wake the page as someone may be waiting on completion of the write. The problem is that the store limit may be updated by a different asynchronous operation - and so may miss the write - and that the store limit may not even get updated until later by the netfs. Fix the kernel hang by making fscache_write_op() mark as written any pages that are over the limit. Signed-off-by: David Howells Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/fscache/page.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/fscache/page.c b/fs/fscache/page.c index 6b35fc4860a0..1de16a5a5c4e 100644 --- a/fs/fscache/page.c +++ b/fs/fscache/page.c @@ -776,6 +776,7 @@ static void fscache_write_op(struct fscache_operation *_op) _enter("{OP%x,%d}", op->op.debug_id, atomic_read(&op->op.usage)); +again: spin_lock(&object->lock); cookie = object->cookie; @@ -816,10 +817,6 @@ static void fscache_write_op(struct fscache_operation *_op) goto superseded; page = results[0]; _debug("gang %d [%lx]", n, page->index); - if (page->index >= op->store_limit) { - fscache_stat(&fscache_n_store_pages_over_limit); - goto superseded; - } radix_tree_tag_set(&cookie->stores, page->index, FSCACHE_COOKIE_STORING_TAG); @@ -829,6 +826,9 @@ static void fscache_write_op(struct fscache_operation *_op) spin_unlock(&cookie->stores_lock); spin_unlock(&object->lock); + if (page->index >= op->store_limit) + goto discard_page; + fscache_stat(&fscache_n_store_pages); fscache_stat(&fscache_n_cop_write_page); ret = object->cache->ops->write_page(op, page); @@ -844,6 +844,11 @@ static void fscache_write_op(struct fscache_operation *_op) _leave(""); return; +discard_page: + fscache_stat(&fscache_n_store_pages_over_limit); + fscache_end_page_write(object, page); + goto again; + superseded: /* this writer is going away and there aren't any more things to * write */