4.9-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ 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 dhowells@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/fscache/page.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
--- a/fs/fscache/page.c +++ b/fs/fscache/page.c @@ -776,6 +776,7 @@ static void fscache_write_op(struct fsca
_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@@ -816,10 +817,6 @@ static void fscache_write_op(struct fsca goto superseded; page = results[0]; _debug("gang %d [%lx]", n, page-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store_limit) { - fscache_stat(&fscache_n_store_pages_over_limit); - goto superseded; - }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 fsca 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 fsca _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+ fscache_stat(&fscache_n_store_pages_over_limit); + fscache_end_page_write(object, page); + goto again; + superseded: /* this writer is going away and there aren't any more things to * write */