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authorJeffle Xu <jefflexu@linux.alibaba.com>2022-04-25 15:21:25 +0300
committerGao Xiang <hsiangkao@linux.alibaba.com>2022-05-17 19:11:17 +0300
commitd11b0b043b4008d64abaf1a26eea3dbcd906ee59 (patch)
treeb09e9f775fefd0ecb0a3dcf1ca4191f7826d8e64 /fs/cachefiles
parentc8383054506c77b814489c09877b5db83fd4abf2 (diff)
downloadlinux-d11b0b043b4008d64abaf1a26eea3dbcd906ee59.tar.xz
cachefiles: unbind cachefiles gracefully in on-demand mode
Add a refcount to avoid the deadlock in on-demand read mode. The on-demand read mode will pin the corresponding cachefiles object for each anonymous fd. The cachefiles object is unpinned when the anonymous fd gets closed. When the user daemon exits and the fd of "/dev/cachefiles" device node gets closed, it will wait for all cahcefiles objects getting withdrawn. Then if there's any anonymous fd getting closed after the fd of the device node, the user daemon will hang forever, waiting for all objects getting withdrawn. To fix this, add a refcount indicating if there's any object pinned by anonymous fds. The cachefiles cache gets unbound and withdrawn when the refcount is decreased to 0. It won't change the behaviour of the original mode, in which case the cachefiles cache gets unbound and withdrawn as long as the fd of the device node gets closed. Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Link: https://lore.kernel.org/r/20220509074028.74954-4-jefflexu@linux.alibaba.com Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Diffstat (limited to 'fs/cachefiles')
-rw-r--r--fs/cachefiles/daemon.c19
-rw-r--r--fs/cachefiles/internal.h3
-rw-r--r--fs/cachefiles/ondemand.c3
3 files changed, 22 insertions, 3 deletions
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index d5417da7f792..5b1d0642c749 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -111,6 +111,7 @@ static int cachefiles_daemon_open(struct inode *inode, struct file *file)
INIT_LIST_HEAD(&cache->volumes);
INIT_LIST_HEAD(&cache->object_list);
spin_lock_init(&cache->object_list_lock);
+ refcount_set(&cache->unbind_pincount, 1);
xa_init_flags(&cache->reqs, XA_FLAGS_ALLOC);
xa_init_flags(&cache->ondemand_ids, XA_FLAGS_ALLOC1);
@@ -164,6 +165,20 @@ static void cachefiles_flush_reqs(struct cachefiles_cache *cache)
xa_destroy(&cache->ondemand_ids);
}
+void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache)
+{
+ if (refcount_dec_and_test(&cache->unbind_pincount)) {
+ cachefiles_daemon_unbind(cache);
+ cachefiles_open = 0;
+ kfree(cache);
+ }
+}
+
+void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache)
+{
+ refcount_inc(&cache->unbind_pincount);
+}
+
/*
* Release a cache.
*/
@@ -179,14 +194,12 @@ static int cachefiles_daemon_release(struct inode *inode, struct file *file)
if (cachefiles_in_ondemand_mode(cache))
cachefiles_flush_reqs(cache);
- cachefiles_daemon_unbind(cache);
/* clean up the control file interface */
cache->cachefilesd = NULL;
file->private_data = NULL;
- cachefiles_open = 0;
- kfree(cache);
+ cachefiles_put_unbind_pincount(cache);
_leave("");
return 0;
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 4f5150a96849..e5c612888f84 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -109,6 +109,7 @@ struct cachefiles_cache {
char *rootdirname; /* name of cache root directory */
char *secctx; /* LSM security context */
char *tag; /* cache binding tag */
+ refcount_t unbind_pincount;/* refcount to do daemon unbind */
struct xarray reqs; /* xarray of pending on-demand requests */
struct xarray ondemand_ids; /* xarray for ondemand_id allocation */
u32 ondemand_id_next;
@@ -171,6 +172,8 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache,
* daemon.c
*/
extern const struct file_operations cachefiles_daemon_fops;
+extern void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache);
+extern void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache);
/*
* error_inject.c
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 64fc312b16d3..7946ee6c40be 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -14,6 +14,7 @@ static int cachefiles_ondemand_fd_release(struct inode *inode,
object->ondemand_id = CACHEFILES_ONDEMAND_ID_CLOSED;
xa_erase(&cache->ondemand_ids, object_id);
cachefiles_put_object(object, cachefiles_obj_put_ondemand_fd);
+ cachefiles_put_unbind_pincount(cache);
return 0;
}
@@ -169,6 +170,8 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
load->fd = fd;
req->msg.object_id = object_id;
object->ondemand_id = object_id;
+
+ cachefiles_get_unbind_pincount(cache);
return 0;
err_put_fd: