For those of you working on fscache.
---------- Forwarded message ----------
From: David Howells <dhowells@xxxxxxxxxx>
Date: Mon, Nov 11, 2013 at 5:18 PM
Subject: [PATCH] FS-Cache: Fix handling of an attempt to store a page
that is now beyond EOF
To: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: linux-cachefs@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Milosz
Tanski <milosz@xxxxxxxxx>
Fix the handling of an attempt to store a page that is now beyond EOF. This
may happen, for example, if the page got pushed for storage before the netfs
file got truncated on the server. In such a case, we should just remove the
excessive pages from the cookie->stores radix tree and wake up the waiter.
This can be seen in /proc/fs/fscache/stats on this line:
Stores : ops=350 run=1895 pgs=1545 rxd=1727 olm=9
where olm=N has N > 0.
Reported-by: Milosz Tanski <milosz@xxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Acked-by: Milosz Tanski <milosz@xxxxxxxxx>
---
fs/fscache/page.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 7f5c658af755..b4730cf52aec 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -755,6 +755,7 @@ static void fscache_write_op(struct fscache_operation *_op)
struct fscache_object *object = op->op.object;
struct fscache_cookie *cookie;
struct page *page;
+ pgoff_t index;
unsigned n;
void *results[1];
int ret;
@@ -803,7 +804,7 @@ static void fscache_write_op(struct fscache_operation *_op)
_debug("gang %d [%lx]", n, page->index);
if (page->index > op->store_limit) {
fscache_stat(&fscache_n_store_pages_over_limit);
- goto superseded;
+ goto page_beyond_limit;
}
radix_tree_tag_set(&cookie->stores, page->index,
@@ -829,6 +830,40 @@ static void fscache_write_op(struct fscache_operation *_op)
_leave("");
return;
+page_beyond_limit:
+ spin_unlock(&object->lock);
+
+page_beyond_limit_unlocked:
+ /* pages that are now beyond the end of the storage object must have
+ * their pending storage records cleared.
+ */
+ index = page->index;
+ radix_tree_tag_clear(&cookie->stores, page->index,
+ FSCACHE_COOKIE_PENDING_TAG);
+ if (!radix_tree_tag_get(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG)) {
+ fscache_stat(&fscache_n_store_radix_deletes);
+ radix_tree_delete(&cookie->stores, page->index);
+ page_cache_release(page);
+ }
+ if (!need_resched()) {
+ n = radix_tree_gang_lookup_tag(&cookie->stores, results,
+ index + 1, 1,
+ FSCACHE_COOKIE_PENDING_TAG);
+ if (n == 1) {
+ page = results[0];
+ goto page_beyond_limit_unlocked;
+ }
+ spin_unlock(&cookie->stores_lock);
+ wake_up_bit(&cookie->flags, 0);
+ } else {
+ spin_unlock(&cookie->stores_lock);
+ }
+
+ fscache_enqueue_operation(&op->op);
+ _leave("");
+ return;
+
superseded:
/* this writer is going away and there aren't any more things to
* write */
--
Milosz Tanski
CTO
10 East 53rd Street, 37th floor
New York, NY 10022
p: 646-253-9055
e: milosz@xxxxxxxxx
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