linux/fs/fuse, branch v5.4

fuse: redundant get_fuse_inode() calls in fuse_writepages_fill()

2019-10-23T12:26:37Z

Currently fuse_writepages_fill() calls get_fuse_inode() few times with the same argument. Signed-off-by: Vasily Averin Signed-off-by: Miklos Szeredi

fuse: truncate pending writes on O_TRUNC

2019-10-23T12:26:37Z

Make sure cached writes are not reordered around open(..., O_TRUNC), with the obvious wrong results. Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on") Cc: # v3.15+ Signed-off-by: Miklos Szeredi

fuse: flush dirty data/metadata before non-truncate setattr

2019-10-23T12:26:37Z

If writeback cache is enabled, then writes might get reordered with chmod/chown/utimes. The problem with this is that performing the write in the fuse daemon might itself change some of these attributes. In such case the following sequence of operations will result in file ending up with the wrong mode, for example: int fd = open ("suid", O_WRONLY|O_CREAT|O_EXCL); write (fd, "1", 1); fchown (fd, 0, 0); fchmod (fd, 04755); close (fd); This patch fixes this by flushing pending writes before performing chown/chmod/utimes. Reported-by: Giuseppe Scrivano Tested-by: Giuseppe Scrivano Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on") Cc: # v3.15+ Signed-off-by: Miklos Szeredi

virtiofs: Remove set but not used variable 'fc'

2019-10-23T08:25:17Z

Fixes gcc '-Wunused-but-set-variable' warning: fs/fuse/virtio_fs.c: In function virtio_fs_wake_pending_and_unlock: fs/fuse/virtio_fs.c:983:20: warning: variable fc set but not used [-Wunused-but-set-variable] It is not used since commit 7ee1e2e631db ("virtiofs: No need to check fpq->connected state") Reported-by: Hulk Robot Signed-off-by: zhengbin Signed-off-by: Miklos Szeredi

virtiofs: Retry request submission from worker context

2019-10-21T13:57:08Z

If regular request queue gets full, currently we sleep for a bit and retrying submission in submitter's context. This assumes submitter is not holding any spin lock. But this assumption is not true for background requests. For background requests, we are called with fc->bg_lock held. This can lead to deadlock where one thread is trying submission with fc->bg_lock held while request completion thread has called fuse_request_end() which tries to acquire fc->bg_lock and gets blocked. As request completion thread gets blocked, it does not make further progress and that means queue does not get empty and submitter can't submit more requests. To solve this issue, retry submission with the help of a worker, instead of retrying in submitter's context. We already do this for hiprio/forget requests. Reported-by: Chirantan Ekbote Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi

virtiofs: Count pending forgets as in_flight forgets

2019-10-21T13:57:07Z

If virtqueue is full, we put forget requests on a list and these forgets are dispatched later using a worker. As of now we don't count these forgets in fsvq->in_flight variable. This means when queue is being drained, we have to have special logic to first drain these pending requests and then wait for fsvq->in_flight to go to zero. By counting pending forgets in fsvq->in_flight, we can get rid of special logic and just wait for in_flight to go to zero. Worker thread will kick and drain all the forgets anyway, leading in_flight to zero. I also need similar logic for normal request queue in next patch where I am about to defer request submission in the worker context if queue is full. This simplifies the code a bit. Also add two helper functions to inc/dec in_flight. Decrement in_flight helper will later used to call completion when in_flight reaches zero. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi

virtiofs: Set FR_SENT flag only after request has been sent

2019-10-21T13:57:07Z

FR_SENT flag should be set when request has been sent successfully sent over virtqueue. This is used by interrupt logic to figure out if interrupt request should be sent or not. Also add it to fqp->processing list after sending it successfully. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi

virtiofs: No need to check fpq->connected state

2019-10-21T13:57:07Z

In virtiofs we keep per queue connected state in virtio_fs_vq->connected and use that to end request if queue is not connected. And virtiofs does not even touch fpq->connected state. We probably need to merge these two at some point of time. For now, simplify the code a bit and do not worry about checking state of fpq->connected. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi

virtiofs: Do not end request in submission context

2019-10-21T13:57:07Z

Submission context can hold some locks which end request code tries to hold again and deadlock can occur. For example, fc->bg_lock. If a background request is being submitted, it might hold fc->bg_lock and if we could not submit request (because device went away) and tried to end request, then deadlock happens. During testing, I also got a warning from deadlock detection code. So put requests on a list and end requests from a worker thread. I got following warning from deadlock detector. [ 603.137138] WARNING: possible recursive locking detected [ 603.137142] -------------------------------------------- [ 603.137144] blogbench/2036 is trying to acquire lock: [ 603.137149] 00000000f0f51107 (&(&fc->bg_lock)->rlock){+.+.}, at: fuse_request_end+0xdf/0x1c0 [fuse] [ 603.140701] [ 603.140701] but task is already holding lock: [ 603.140703] 00000000f0f51107 (&(&fc->bg_lock)->rlock){+.+.}, at: fuse_simple_background+0x92/0x1d0 [fuse] [ 603.140713] [ 603.140713] other info that might help us debug this: [ 603.140714] Possible unsafe locking scenario: [ 603.140714] [ 603.140715] CPU0 [ 603.140716] ---- [ 603.140716] lock(&(&fc->bg_lock)->rlock); [ 603.140718] lock(&(&fc->bg_lock)->rlock); [ 603.140719] [ 603.140719] *** DEADLOCK *** Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi

fuse: don't advise readdirplus for negative lookup

2019-10-21T13:57:07Z

If the FUSE_READDIRPLUS_AUTO feature is enabled, then lookups on a directory before/during readdir are used as an indication that READDIRPLUS should be used instead of READDIR. However if the lookup turns out to be negative, then selecting READDIRPLUS makes no sense. Signed-off-by: Miklos Szeredi