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Sat, 9 Jan 2021 02:08:46 +0000 (UTC) Received: from [10.72.12.57] (ovpn-12-57.pek2.redhat.com [10.72.12.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C892A1754A; Sat, 9 Jan 2021 02:08:44 +0000 (UTC) Subject: Re: [PATCH v2] ceph: defer flushing the capsnap if the Fb is used To: Jeff Layton Cc: idryomov@gmail.com, pdonnell@redhat.com, ceph-devel@vger.kernel.org References: <20210107023051.119063-1-xiubli@redhat.com> <97ec811665eee254627c46d7999818fd94bab9ed.camel@kernel.org> From: Xiubo Li Message-ID: Date: Sat, 9 Jan 2021 10:08:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <97ec811665eee254627c46d7999818fd94bab9ed.camel@kernel.org> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On 2021/1/9 2:24, Jeff Layton wrote: > On Thu, 2021-01-07 at 10:30 +0800, xiubli@redhat.com wrote: >> From: Xiubo Li >> >> If the Fb cap is used it means the client is flushing the dirty >> data to OSD, just defer flushing the capsnap. >> >> URL: https://tracker.ceph.com/issues/48679 >> URL: https://tracker.ceph.com/issues/48640 >> Signed-off-by: Xiubo Li >> --- >> >> V2: >> - Fix inode reference leak bug >> >>  fs/ceph/caps.c | 32 +++++++++++++++++++------------- >>  fs/ceph/snap.c | 6 +++--- >>  2 files changed, 22 insertions(+), 16 deletions(-) >> >> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c >> index abbf48fc6230..2f2451d563bd 100644 >> --- a/fs/ceph/caps.c >> +++ b/fs/ceph/caps.c >> @@ -3047,6 +3047,7 @@ static void __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; >> + bool check_flushsnaps = false; >> >> >> >> >>   spin_lock(&ci->i_ceph_lock); >>   if (had & CEPH_CAP_PIN) >> @@ -3064,25 +3065,15 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had, >>   if (--ci->i_wb_ref == 0) { >>   last++; >>   put++; >> + check_flushsnaps = true; >>   } >>   dout("put_cap_refs %p wb %d -> %d (?)\n", >>   inode, ci->i_wb_ref+1, ci->i_wb_ref); >>   } >> - if (had & CEPH_CAP_FILE_WR) >> + if (had & CEPH_CAP_FILE_WR) { >>   if (--ci->i_wr_ref == 0) { >>   last++; >> - if (__ceph_have_pending_cap_snap(ci)) { >> - struct ceph_cap_snap *capsnap = >> - list_last_entry(&ci->i_cap_snaps, >> - struct ceph_cap_snap, >> - ci_item); >> - capsnap->writing = 0; >> - if (ceph_try_drop_cap_snap(ci, capsnap)) >> - put++; >> - else if (__ceph_finish_cap_snap(ci, capsnap)) >> - flushsnaps = 1; >> - wake = 1; >> - } >> + check_flushsnaps = true; >>   if (ci->i_wrbuffer_ref_head == 0 && >>   ci->i_dirty_caps == 0 && >>   ci->i_flushing_caps == 0) { >> @@ -3094,6 +3085,21 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had, >>   if (!__ceph_is_any_real_caps(ci) && ci->i_snap_realm) >>   drop_inode_snap_realm(ci); >>   } >> + } >> + if (check_flushsnaps) { >> + if (__ceph_have_pending_cap_snap(ci)) { >> + struct ceph_cap_snap *capsnap = >> + list_last_entry(&ci->i_cap_snaps, >> + struct ceph_cap_snap, >> + ci_item); >> + capsnap->writing = 0; >> + if (ceph_try_drop_cap_snap(ci, capsnap)) >> + put++; >> + else if (__ceph_finish_cap_snap(ci, capsnap)) >> + flushsnaps = 1; >> + wake = 1; >> + } >> + } > > Ok, so let's assume you're putting Fb. You increment put and set > check_flushsnaps to true. Later, you get down to here and call > ceph_try_drop_cap_snap and it returns true and now you've incremented > "put" twice. > > Is that right? Do Fb caps hold two inode references? Yeah, one in ceph_take_cap_refs(). Another one is in ceph_queue_cap_snap() and when `used & (Fb | Fw)` is true, the flush capsnap will be delayed by holding the inode ref, so we need to put the inode ref here or in __ceph_finish_cap_snap(). > Either way, I think this function needs some better > documentation/comments, particularly since you're making a significant > change to how it works. Okay, I will post the V3 after my back later to add more comments about this. Thanks > >>   spin_unlock(&ci->i_ceph_lock); >> >> >> >> >>   dout("put_cap_refs %p had %s%s%s\n", inode, ceph_cap_string(had), >> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c >> index b611f829cb61..639fb91cc9db 100644 >> --- a/fs/ceph/snap.c >> +++ b/fs/ceph/snap.c >> @@ -561,10 +561,10 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) >>   capsnap->context = old_snapc; >>   list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps); >> >> >> >> >> - if (used & CEPH_CAP_FILE_WR) { >> + if (used & (CEPH_CAP_FILE_WR | CEPH_CAP_FILE_BUFFER)) { >>   dout("queue_cap_snap %p cap_snap %p snapc %p" >> - " seq %llu used WR, now pending\n", inode, >> - capsnap, old_snapc, old_snapc->seq); >> + " seq %llu used WR | BUFFFER, now pending\n", >> + inode, capsnap, old_snapc, old_snapc->seq); >>   capsnap->writing = 1; >>   } else { >>   /* note mtime, size NOW. */