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authorDavid Howells <dhowells@redhat.com>2018-04-04 13:41:26 +0100
committerDavid Howells <dhowells@redhat.com>2018-04-04 13:41:26 +0100
commit2c98425720233ae3e135add0c7e869b32913502f (patch)
tree100789f2ccb035a3ec3bbfc76d6a63eaeedf18d8
parentd0fb31ecda2c3c6092d0c2a46a6a72653e7dcabb (diff)
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fscache: Fix hanging wait on page discarded by writeback
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>
-rw-r--r--fs/fscache/page.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index adc39c0c62df..b9f18bf4227d 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -778,6 +778,7 @@ 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;
@@ -819,10 +820,6 @@ 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goto superseded;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- goto superseded;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);
@@ -832,6 +829,9 @@ 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);
@@ -847,6 +847,11 @@ 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superseded: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 */