From mboxrd@z Thu Jan 1 00:00:00 1970 From: xiubli@redhat.com Subject: [PATCH v3 1/2] ceph: add ceph_async_put_cap_refs to avoid double lock and deadlock Date: Tue, 26 May 2020 21:42:35 -0400 Message-ID: <1590543756-26773-2-git-send-email-xiubli@redhat.com> References: <1590543756-26773-1-git-send-email-xiubli@redhat.com> Return-path: Received: from us-smtp-2.mimecast.com ([205.139.110.61]:21354 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725801AbgE0Bmx (ORCPT ); Tue, 26 May 2020 21:42:53 -0400 In-Reply-To: <1590543756-26773-1-git-send-email-xiubli@redhat.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: jlayton@kernel.org, idryomov@gmail.com, zyan@redhat.com Cc: pdonnell@redhat.com, ceph-devel@vger.kernel.org, Xiubo Li From: Xiubo Li In the ceph_check_caps() it may call the session->s_mutex lock/unlock and in ceph_flush_snaps() it may call the mdsc->mutex lock/unlock. And both of them called from ceph_mdsc_put_request(), which may under the session or mdsc mutex lock/unlock pair already, we will hit the dead lock or double lock issue. There have some deadlock cases, like: handle_forward() ... mutex_lock(&mdsc->mutex) ... ceph_mdsc_put_request() --> ceph_mdsc_release_request() --> ceph_put_cap_request() --> ceph_put_cap_refs() --> ceph_check_caps() ... mutex_unlock(&mdsc->mutex) And also there maybe has some double session lock cases, like: send_mds_reconnect() ... mutex_lock(&session->s_mutex); ... --> replay_unsafe_requests() --> ceph_mdsc_release_dir_caps() --> ceph_put_cap_refs() --> ceph_check_caps() ... mutex_unlock(&session->s_mutex); This patch will just delays to call them in a queue work to avoid the dead lock and double lock issues. URL: https://tracker.ceph.com/issues/45635 Signed-off-by: Xiubo Li --- fs/ceph/caps.c | 89 ++++++++++++++++++++++++++++++++++++++++++++-------- fs/ceph/inode.c | 3 ++ fs/ceph/mds_client.c | 2 +- fs/ceph/super.h | 5 +++ 4 files changed, 85 insertions(+), 14 deletions(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 27c2e60..996bedb 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "super.h" #include "mds_client.h" @@ -3007,19 +3008,15 @@ static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci, return 0; } -/* - * Release cap refs. - * - * If we released the last ref on any given cap, call ceph_check_caps - * to release (or schedule a release). - * - * If we are releasing a WR cap (from a sync write), finalize any affected - * cap_snap, and wake up any waiters. - */ -void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) +#define CAP_REF_LAST_BIT 0 +#define CAP_REF_FLUSHSNAPS_BIT 1 +#define CAP_REF_WAKE_BIT 2 + +static int __ceph_put_cap_refs(struct ceph_inode_info *ci, int had) { struct inode *inode = &ci->vfs_inode; int last = 0, put = 0, flushsnaps = 0, wake = 0; + unsigned long flags = 0; spin_lock(&ci->i_ceph_lock); if (had & CEPH_CAP_PIN) @@ -3073,13 +3070,79 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) last ? " last" : "", put ? " put" : ""); if (last) - ceph_check_caps(ci, 0, NULL); + set_bit(CAP_REF_LAST_BIT, &flags); else if (flushsnaps) - ceph_flush_snaps(ci, NULL); + set_bit(CAP_REF_FLUSHSNAPS_BIT, &flags); if (wake) - wake_up_all(&ci->i_cap_wq); + set_bit(CAP_REF_WAKE_BIT, &flags); while (put-- > 0) iput(inode); + + return flags; +} + +/* + * This is the bottow half of __ceph_put_cap_refs(), which + * may take the mdsc->mutex and session->s_mutex and this + * will be called in a queue work to void dead/double lock + * issues if called from ceph_mdsc_put_request(). + */ +static void __ceph_put_cap_refs_bh(struct ceph_inode_info *ci, + unsigned long flags) +{ + if (test_bit(CAP_REF_LAST_BIT, &flags)) + ceph_check_caps(ci, 0, NULL); + else if (test_bit(CAP_REF_FLUSHSNAPS_BIT, &flags)) + ceph_flush_snaps(ci, NULL); + if (test_bit(CAP_REF_WAKE_BIT, &flags)) + wake_up_all(&ci->i_cap_wq); +} + +/* + * Release cap refs. + * + * If we released the last ref on any given cap, call ceph_check_caps + * to release (or schedule a release). + * + * If we are releasing a WR cap (from a sync write), finalize any affected + * cap_snap, and wake up any waiters. + */ +void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) +{ + unsigned long flags; + + flags = __ceph_put_cap_refs(ci, had); + __ceph_put_cap_refs_bh(ci, flags); +} + +void ceph_async_put_cap_refs_work(struct work_struct *work) +{ + struct ceph_inode_info *ci = container_of(work, struct ceph_inode_info, + put_cap_refs_work); + unsigned long flags; + + spin_lock(&ci->i_ceph_lock); + flags = xchg(&ci->pending_put_flags, 0); + spin_unlock(&ci->i_ceph_lock); + if (!flags) + return; + + __ceph_put_cap_refs_bh(ci, flags); +} + +void ceph_async_put_cap_refs(struct ceph_inode_info *ci, int had) +{ + struct inode *inode = &ci->vfs_inode; + unsigned long flags; + + flags = __ceph_put_cap_refs(ci, had); + + spin_lock(&ci->i_ceph_lock); + ci->pending_put_flags |= flags; + spin_unlock(&ci->i_ceph_lock); + + queue_work(ceph_inode_to_client(inode)->inode_wq, + &ci->put_cap_refs_work); } /* diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c index 357c937..e0ea508 100644 --- a/fs/ceph/inode.c +++ b/fs/ceph/inode.c @@ -517,6 +517,9 @@ struct inode *ceph_alloc_inode(struct super_block *sb) INIT_LIST_HEAD(&ci->i_snap_realm_item); INIT_LIST_HEAD(&ci->i_snap_flush_item); + INIT_WORK(&ci->put_cap_refs_work, ceph_async_put_cap_refs_work); + ci->pending_put_flags = 0; + INIT_WORK(&ci->i_work, ceph_inode_work); ci->i_work_mask = 0; memset(&ci->i_btime, '\0', sizeof(ci->i_btime)); diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 0e0ab01..12506b7 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -3398,7 +3398,7 @@ void ceph_mdsc_release_dir_caps(struct ceph_mds_request *req) dcaps = xchg(&req->r_dir_caps, 0); if (dcaps) { dout("releasing r_dir_caps=%s\n", ceph_cap_string(dcaps)); - ceph_put_cap_refs(ceph_inode(req->r_parent), dcaps); + ceph_async_put_cap_refs(ceph_inode(req->r_parent), dcaps); } } diff --git a/fs/ceph/super.h b/fs/ceph/super.h index 226f19c..ece94fc 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -421,6 +421,9 @@ struct ceph_inode_info { struct timespec64 i_btime; struct timespec64 i_snap_btime; + struct work_struct put_cap_refs_work; + unsigned long pending_put_flags; + struct work_struct i_work; unsigned long i_work_mask; @@ -1095,6 +1098,8 @@ extern void ceph_take_cap_refs(struct ceph_inode_info *ci, int caps, bool snap_rwsem_locked); extern void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps); extern void ceph_put_cap_refs(struct ceph_inode_info *ci, int had); +extern void ceph_async_put_cap_refs(struct ceph_inode_info *ci, int had); +extern void ceph_async_put_cap_refs_work(struct work_struct *work); extern void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr, struct ceph_snap_context *snapc); extern void ceph_flush_snaps(struct ceph_inode_info *ci, -- 1.8.3.1