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commit fd3b3e0ec59db813d3ff665e158b1390ecdcfd14
parent 38c7b224ce22c25fed04007839edf974bd13439d
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 30 Nov 2018 18:32:33 -0800

Merge tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull fscache and cachefiles fixes from David Howells:
 "Misc fixes:

   - Fix an assertion failure at fs/cachefiles/xattr.c:138 caused by a
     race between a cache object lookup failing and someone attempting
     to reenable that object, thereby triggering an update of the
     object's attributes.

   - Fix an assertion failure at fs/fscache/operation.c:449 caused by a
     split atomic subtract and atomic read that allows a race to happen.

   - Fix a leak of backing pages when simultaneously reading the same
     page from the same object from two or more threads.

   - Fix a hang due to a race between a cache object being discarded and
     the corresponding cookie being reenabled.

  There are also some minor cleanups:

   - Cast an enum value to a different enum type to prevent clang from
     generating a warning. This shouldn't cause any sort of change in
     the emitted code.

   - Use ktime_get_real_seconds() instead of get_seconds(). This is just
     used to uniquify a filename for an object to be placed in the
     graveyard. Objects placed there are deleted by cachfilesd in
     userspace immediately thereafter.

   - Remove an initialised, but otherwise unused variable. This should
     have been entirely optimised away anyway"

* tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  fscache, cachefiles: remove redundant variable 'cache'
  cachefiles: avoid deprecated get_seconds()
  cachefiles: Explicitly cast enumerated type in put_object
  fscache: fix race between enablement and dropping of object
  cachefiles: Fix page leak in cachefiles_read_backing_file while vmscan is active
  fscache: Fix race in fscache_op_complete() due to split atomic_sub & read
  cachefiles: Fix an assertion failure when trying to update a failed object

Diffstat:
Mfs/cachefiles/namei.c | 8+++++---
Mfs/cachefiles/rdwr.c | 9++++++---
Mfs/cachefiles/xattr.c | 3++-
Mfs/fscache/object.c | 3+++
Minclude/linux/fscache-cache.h | 3+--
5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c @@ -244,11 +244,13 @@ wait_for_old_object: ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)); - cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_retry); + cache->cache.ops->put_object(&xobject->fscache, + (enum fscache_obj_ref_trace)cachefiles_obj_put_wait_retry); goto try_again; requeue: - cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_timeo); + cache->cache.ops->put_object(&xobject->fscache, + (enum fscache_obj_ref_trace)cachefiles_obj_put_wait_timeo); _leave(" = -ETIMEDOUT"); return -ETIMEDOUT; } @@ -336,7 +338,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache, try_again: /* first step is to make up a grave dentry in the graveyard */ sprintf(nbuffer, "%08x%08x", - (uint32_t) get_seconds(), + (uint32_t) ktime_get_real_seconds(), (uint32_t) atomic_inc_return(&cache->gravecounter)); /* do the multiway lock magic */ diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c @@ -535,7 +535,10 @@ static int cachefiles_read_backing_file(struct cachefiles_object *object, netpage->index, cachefiles_gfp); if (ret < 0) { if (ret == -EEXIST) { + put_page(backpage); + backpage = NULL; put_page(netpage); + netpage = NULL; fscache_retrieval_complete(op, 1); continue; } @@ -608,7 +611,10 @@ static int cachefiles_read_backing_file(struct cachefiles_object *object, netpage->index, cachefiles_gfp); if (ret < 0) { if (ret == -EEXIST) { + put_page(backpage); + backpage = NULL; put_page(netpage); + netpage = NULL; fscache_retrieval_complete(op, 1); continue; } @@ -962,11 +968,8 @@ void cachefiles_uncache_page(struct fscache_object *_object, struct page *page) __releases(&object->fscache.cookie->lock) { struct cachefiles_object *object; - struct cachefiles_cache *cache; object = container_of(_object, struct cachefiles_object, fscache); - cache = container_of(object->fscache.cache, - struct cachefiles_cache, cache); _enter("%p,{%lu}", object, page->index); diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c @@ -135,7 +135,8 @@ int cachefiles_update_object_xattr(struct cachefiles_object *object, struct dentry *dentry = object->dentry; int ret; - ASSERT(dentry); + if (!dentry) + return -ESTALE; _enter("%p,#%d", object, auxdata->len); diff --git a/fs/fscache/object.c b/fs/fscache/object.c @@ -730,6 +730,9 @@ static const struct fscache_state *fscache_drop_object(struct fscache_object *ob if (awaken) wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING); + if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags)) + wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP); + /* Prevent a race with our last child, which has to signal EV_CLEARED * before dropping our spinlock. diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h @@ -196,8 +196,7 @@ static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) static inline void fscache_retrieval_complete(struct fscache_retrieval *op, int n_pages) { - atomic_sub(n_pages, &op->n_pages); - if (atomic_read(&op->n_pages) <= 0) + if (atomic_sub_return_relaxed(n_pages, &op->n_pages) <= 0) fscache_op_complete(&op->op, false); }