| Message ID | CAN-5tyHxP276Re_Zm4mV9F+EY1Czq5SfbPJ1Os_CQd0hfhFzdA@mail.gmail.com (mailing list archive) |
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On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> It'll be nice to know when we return delegations synchronously or not.
Why? This patch forces us to carry an otherwise completely unnecessary
parameter, so at the very minimum we should have a discussion of what
the real use cases are.
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On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote: > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> It'll be nice to know when we return delegations synchronously or not. > > Why? This patch forces us to carry an otherwise completely unnecessary > parameter, so at the very minimum we should have a discussion of what > the real use cases are. I used it to diagnose the race of open and delegreturn. If it's kept that some delegreturns are synchronous and others are not I think the information is useful. Speaking of there is a race between state manager thread returning used delegations and new open. Previously I thought it was evict inode... > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: > > On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust > <trond.myklebust@primarydata.com> wrote: > > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > >> It'll be nice to know when we return delegations synchronously or not. > > > > Why? This patch forces us to carry an otherwise completely unnecessary > > parameter, so at the very minimum we should have a discussion of what > > the real use cases are. > > I used it to diagnose the race of open and delegreturn. If it's kept How were you using it? > that some delegreturns are synchronous and others are not I think the > information is useful. The only difference between synchronous and asynchronous in this case is whether or not the process that launched the delegreturn actually waits for it to complete; a signal could easily prevent it from doing so without interrupting the delegreturn call itself. IOW: for complete information when debugging races here, you really need to examine the return value from the wait call. > Speaking of there is a race between state manager thread returning > used delegations and new open. Previously I thought it was evict > inode... Is this with commit 5e99b532bb95 ("nfs4: reset states to use open_stateid when returning delegation voluntarily") applied? -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust <trond.myklebust@primarydata.com> wrote: > On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >> <trond.myklebust@primarydata.com> wrote: >> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >> It'll be nice to know when we return delegations synchronously or not. >> > >> > Why? This patch forces us to carry an otherwise completely unnecessary >> > parameter, so at the very minimum we should have a discussion of what >> > the real use cases are. >> >> I used it to diagnose the race of open and delegreturn. If it's kept > > How were you using it? I added two more traces points in the beginning of delegreturn and in nfs4_do_open before sending the rpc. I can see that a given file handle: -- delegreturn prepare tracepoint is happening, -- then the tracepoint of before sending the open is logged, -- then delegreturn prepare is logged again, -- then tracepoint for nfs4_open_file which is after receiving reply to the open from the server -- then delegreturn_exit tracepoint kworker/1:0H-14168 [001] .... 576.571636: nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 issync=0 hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 fhandle=0x00000000 name=00:2a:904/000002CB.ham hammer-13955 [001] .... 577.043084: nfs4_open_file: error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 fhandle=0x84792ca9 name=00:2a:904/000002CB.ham kworker/0:1H-431 [000] .... 577.064013: nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 issync=0 kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: error=0 (OK) dev=00:2a fhandle=0x84792ca9 kworker/0:1H-431 [000] .... 577.113021: nfs4_read: error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 offset=0 count=64 > >> that some delegreturns are synchronous and others are not I think the >> information is useful. > > The only difference between synchronous and asynchronous in this case > is whether or not the process that launched the delegreturn actually > waits for it to complete; a signal could easily prevent it from doing > so without interrupting the delegreturn call itself. > IOW: for complete information when debugging races here, you really > need to examine the return value from the wait call. > >> Speaking of there is a race between state manager thread returning >> used delegations and new open. Previously I thought it was evict >> inode... > > Is this with commit 5e99b532bb95 ("nfs4: reset states to use > open_stateid when returning delegation voluntarily") applied? No I have not. I will try that. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: > On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust > <trond.myklebust@primarydata.com> wrote: >> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >>> <trond.myklebust@primarydata.com> wrote: >>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >> It'll be nice to know when we return delegations synchronously or not. >>> > >>> > Why? This patch forces us to carry an otherwise completely unnecessary >>> > parameter, so at the very minimum we should have a discussion of what >>> > the real use cases are. >>> >>> I used it to diagnose the race of open and delegreturn. If it's kept >> >> How were you using it? > > I added two more traces points in the beginning of delegreturn and in > nfs4_do_open before sending the rpc. I can see that a given file > handle: > -- delegreturn prepare tracepoint is happening, > -- then the tracepoint of before sending the open is logged, > -- then delegreturn prepare is logged again, > -- then tracepoint for nfs4_open_file which is after receiving reply > to the open from the server > -- then delegreturn_exit tracepoint > > kworker/1:0H-14168 [001] .... 576.571636: > nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 > issync=0 > > hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: > flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 > fhandle=0x00000000 name=00:2a:904/000002CB.ham > > hammer-13955 [001] .... 577.043084: nfs4_open_file: > error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 > fhandle=0x84792ca9 name=00:2a:904/000002CB.ham > > kworker/0:1H-431 [000] .... 577.064013: > nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 > issync=0 > > kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: > error=0 (OK) dev=00:2a fhandle=0x84792ca9 > > kworker/0:1H-431 [000] .... 577.113021: nfs4_read: > error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 > offset=0 count=64 > > >> >>> that some delegreturns are synchronous and others are not I think the >>> information is useful. >> >> The only difference between synchronous and asynchronous in this case >> is whether or not the process that launched the delegreturn actually >> waits for it to complete; a signal could easily prevent it from doing >> so without interrupting the delegreturn call itself. >> IOW: for complete information when debugging races here, you really >> need to examine the return value from the wait call. >> >>> Speaking of there is a race between state manager thread returning >>> used delegations and new open. Previously I thought it was evict >>> inode... >> >> Is this with commit 5e99b532bb95 ("nfs4: reset states to use >> open_stateid when returning delegation voluntarily") applied? > > No I have not. I will try that. Thanks. This patch does not help. The race is still present. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 12:24 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >> On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust >> <trond.myklebust@primarydata.com> wrote: >>> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>>> >>>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >>>> <trond.myklebust@primarydata.com> wrote: >>>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>>> >> It'll be nice to know when we return delegations synchronously or not. >>>> > >>>> > Why? This patch forces us to carry an otherwise completely unnecessary >>>> > parameter, so at the very minimum we should have a discussion of what >>>> > the real use cases are. >>>> >>>> I used it to diagnose the race of open and delegreturn. If it's kept >>> >>> How were you using it? >> >> I added two more traces points in the beginning of delegreturn and in >> nfs4_do_open before sending the rpc. I can see that a given file >> handle: >> -- delegreturn prepare tracepoint is happening, >> -- then the tracepoint of before sending the open is logged, >> -- then delegreturn prepare is logged again, >> -- then tracepoint for nfs4_open_file which is after receiving reply >> to the open from the server >> -- then delegreturn_exit tracepoint >> >> kworker/1:0H-14168 [001] .... 576.571636: >> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> issync=0 >> >> hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: >> flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 >> fhandle=0x00000000 name=00:2a:904/000002CB.ham >> >> hammer-13955 [001] .... 577.043084: nfs4_open_file: >> error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 >> fhandle=0x84792ca9 name=00:2a:904/000002CB.ham >> >> kworker/0:1H-431 [000] .... 577.064013: >> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> issync=0 >> >> kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: >> error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> >> kworker/0:1H-431 [000] .... 577.113021: nfs4_read: >> error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 >> offset=0 count=64 >> >> >>> >>>> that some delegreturns are synchronous and others are not I think the >>>> information is useful. >>> >>> The only difference between synchronous and asynchronous in this case >>> is whether or not the process that launched the delegreturn actually >>> waits for it to complete; a signal could easily prevent it from doing >>> so without interrupting the delegreturn call itself. >>> IOW: for complete information when debugging races here, you really >>> need to examine the return value from the wait call. >>> >>>> Speaking of there is a race between state manager thread returning >>>> used delegations and new open. Previously I thought it was evict >>>> inode... >>> >>> Is this with commit 5e99b532bb95 ("nfs4: reset states to use >>> open_stateid when returning delegation voluntarily") applied? >> >> No I have not. I will try that. Thanks. > > This patch does not help. The race is still present. OK. So what are the symptoms? I'm having trouble seeing how a race can happen, given a correctly coded server. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 12:56 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote: > On Tue, Oct 13, 2015 at 12:24 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust >>> <trond.myklebust@primarydata.com> wrote: >>>> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>>>> >>>>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >>>>> <trond.myklebust@primarydata.com> wrote: >>>>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>>>> >> It'll be nice to know when we return delegations synchronously or not. >>>>> > >>>>> > Why? This patch forces us to carry an otherwise completely unnecessary >>>>> > parameter, so at the very minimum we should have a discussion of what >>>>> > the real use cases are. >>>>> >>>>> I used it to diagnose the race of open and delegreturn. If it's kept >>>> >>>> How were you using it? >>> >>> I added two more traces points in the beginning of delegreturn and in >>> nfs4_do_open before sending the rpc. I can see that a given file >>> handle: >>> -- delegreturn prepare tracepoint is happening, >>> -- then the tracepoint of before sending the open is logged, >>> -- then delegreturn prepare is logged again, >>> -- then tracepoint for nfs4_open_file which is after receiving reply >>> to the open from the server >>> -- then delegreturn_exit tracepoint >>> >>> kworker/1:0H-14168 [001] .... 576.571636: >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> issync=0 >>> >>> hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: >>> flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 >>> fhandle=0x00000000 name=00:2a:904/000002CB.ham >>> >>> hammer-13955 [001] .... 577.043084: nfs4_open_file: >>> error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 >>> fhandle=0x84792ca9 name=00:2a:904/000002CB.ham >>> >>> kworker/0:1H-431 [000] .... 577.064013: >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> issync=0 >>> >>> kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: >>> error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> >>> kworker/0:1H-431 [000] .... 577.113021: nfs4_read: >>> error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 >>> offset=0 count=64 >>> >>> >>>> >>>>> that some delegreturns are synchronous and others are not I think the >>>>> information is useful. >>>> >>>> The only difference between synchronous and asynchronous in this case >>>> is whether or not the process that launched the delegreturn actually >>>> waits for it to complete; a signal could easily prevent it from doing >>>> so without interrupting the delegreturn call itself. >>>> IOW: for complete information when debugging races here, you really >>>> need to examine the return value from the wait call. >>>> >>>>> Speaking of there is a race between state manager thread returning >>>>> used delegations and new open. Previously I thought it was evict >>>>> inode... >>>> >>>> Is this with commit 5e99b532bb95 ("nfs4: reset states to use >>>> open_stateid when returning delegation voluntarily") applied? >>> >>> No I have not. I will try that. Thanks. >> >> This patch does not help. The race is still present. > > OK. So what are the symptoms? I'm having trouble seeing how a race can > happen, given a correctly coded server. Here's what the server sees: open (foobar) replies back with a delegation various operations including a close() some time goes by... open (foobar) replies back with the same delegation delegreturn read (foobar) using delegation Here's what the client does: open (foobar) gets a delegation, stores is various operations close (file) state manager thread kicks off and marks delegation to be returned -- at this point there are various that could have happened here. one of which is delegation could be removed from the inode but delegreturn is not yet on the wire. or it could mark the delegations unreferenced but not yet return them as a new open comes in. a new open could actually mark the delegation referenced but the state manager when it regains control will proceed with returning it. there is no check in nfs_do_return_delegation() that the delegation is referenced again. but that's not the problem hit here i think. same time another open comes -- if delegation is removed from the inode, the open just proceeds. -- say delegation is not yet removed from the inode but marked RETURNING, the open won't use it but still proceeds with doing the operation and it can (and does) goes on the wire before delegreturn. Delegation->flags is a shared variable accessed by both state manager thread and any other thread but it's never accessed under a lock. That just seems wrong. Shouldn't there be synchronization between returning the delegation and new opens? In VFS code, evict inode code and new open are synchronize that way. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 1:23 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > > On Tue, Oct 13, 2015 at 12:56 PM, Trond Myklebust > <trond.myklebust@primarydata.com> wrote: > > On Tue, Oct 13, 2015 at 12:24 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > >> On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: > >>> On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust > >>> <trond.myklebust@primarydata.com> wrote: > >>>> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: > >>>>> > >>>>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust > >>>>> <trond.myklebust@primarydata.com> wrote: > >>>>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > >>>>> >> It'll be nice to know when we return delegations synchronously or not. > >>>>> > > >>>>> > Why? This patch forces us to carry an otherwise completely unnecessary > >>>>> > parameter, so at the very minimum we should have a discussion of what > >>>>> > the real use cases are. > >>>>> > >>>>> I used it to diagnose the race of open and delegreturn. If it's kept > >>>> > >>>> How were you using it? > >>> > >>> I added two more traces points in the beginning of delegreturn and in > >>> nfs4_do_open before sending the rpc. I can see that a given file > >>> handle: > >>> -- delegreturn prepare tracepoint is happening, > >>> -- then the tracepoint of before sending the open is logged, > >>> -- then delegreturn prepare is logged again, > >>> -- then tracepoint for nfs4_open_file which is after receiving reply > >>> to the open from the server > >>> -- then delegreturn_exit tracepoint > >>> > >>> kworker/1:0H-14168 [001] .... 576.571636: > >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 > >>> issync=0 > >>> > >>> hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: > >>> flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 > >>> fhandle=0x00000000 name=00:2a:904/000002CB.ham > >>> > >>> hammer-13955 [001] .... 577.043084: nfs4_open_file: > >>> error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 > >>> fhandle=0x84792ca9 name=00:2a:904/000002CB.ham > >>> > >>> kworker/0:1H-431 [000] .... 577.064013: > >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 > >>> issync=0 > >>> > >>> kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: > >>> error=0 (OK) dev=00:2a fhandle=0x84792ca9 > >>> > >>> kworker/0:1H-431 [000] .... 577.113021: nfs4_read: > >>> error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 > >>> offset=0 count=64 > >>> > >>> > >>>> > >>>>> that some delegreturns are synchronous and others are not I think the > >>>>> information is useful. > >>>> > >>>> The only difference between synchronous and asynchronous in this case > >>>> is whether or not the process that launched the delegreturn actually > >>>> waits for it to complete; a signal could easily prevent it from doing > >>>> so without interrupting the delegreturn call itself. > >>>> IOW: for complete information when debugging races here, you really > >>>> need to examine the return value from the wait call. > >>>> > >>>>> Speaking of there is a race between state manager thread returning > >>>>> used delegations and new open. Previously I thought it was evict > >>>>> inode... > >>>> > >>>> Is this with commit 5e99b532bb95 ("nfs4: reset states to use > >>>> open_stateid when returning delegation voluntarily") applied? > >>> > >>> No I have not. I will try that. Thanks. > >> > >> This patch does not help. The race is still present. > > > > OK. So what are the symptoms? I'm having trouble seeing how a race can > > happen, given a correctly coded server. > > Here's what the server sees: > open (foobar) replies back with a delegation > various operations including a close() > some time goes by... > open (foobar) replies back with the same delegation Why? Olga, we already had this discussion. That sort of server behaviour is never going to work without races and is the root cause of your problem. We simply won't ever support servers that do this. > delegreturn > read (foobar) using delegation -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 1:28 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote: > On Tue, Oct 13, 2015 at 1:23 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >> On Tue, Oct 13, 2015 at 12:56 PM, Trond Myklebust >> <trond.myklebust@primarydata.com> wrote: >> > On Tue, Oct 13, 2015 at 12:24 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >> On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >>> On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust >> >>> <trond.myklebust@primarydata.com> wrote: >> >>>> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >>>>> >> >>>>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >> >>>>> <trond.myklebust@primarydata.com> wrote: >> >>>>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >> >>>>> >> It'll be nice to know when we return delegations synchronously or not. >> >>>>> > >> >>>>> > Why? This patch forces us to carry an otherwise completely unnecessary >> >>>>> > parameter, so at the very minimum we should have a discussion of what >> >>>>> > the real use cases are. >> >>>>> >> >>>>> I used it to diagnose the race of open and delegreturn. If it's kept >> >>>> >> >>>> How were you using it? >> >>> >> >>> I added two more traces points in the beginning of delegreturn and in >> >>> nfs4_do_open before sending the rpc. I can see that a given file >> >>> handle: >> >>> -- delegreturn prepare tracepoint is happening, >> >>> -- then the tracepoint of before sending the open is logged, >> >>> -- then delegreturn prepare is logged again, >> >>> -- then tracepoint for nfs4_open_file which is after receiving reply >> >>> to the open from the server >> >>> -- then delegreturn_exit tracepoint >> >>> >> >>> kworker/1:0H-14168 [001] .... 576.571636: >> >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> >>> issync=0 >> >>> >> >>> hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: >> >>> flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 >> >>> fhandle=0x00000000 name=00:2a:904/000002CB.ham >> >>> >> >>> hammer-13955 [001] .... 577.043084: nfs4_open_file: >> >>> error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 >> >>> fhandle=0x84792ca9 name=00:2a:904/000002CB.ham >> >>> >> >>> kworker/0:1H-431 [000] .... 577.064013: >> >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> >>> issync=0 >> >>> >> >>> kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: >> >>> error=0 (OK) dev=00:2a fhandle=0x84792ca9 >> >>> >> >>> kworker/0:1H-431 [000] .... 577.113021: nfs4_read: >> >>> error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 >> >>> offset=0 count=64 >> >>> >> >>> >> >>>> >> >>>>> that some delegreturns are synchronous and others are not I think the >> >>>>> information is useful. >> >>>> >> >>>> The only difference between synchronous and asynchronous in this case >> >>>> is whether or not the process that launched the delegreturn actually >> >>>> waits for it to complete; a signal could easily prevent it from doing >> >>>> so without interrupting the delegreturn call itself. >> >>>> IOW: for complete information when debugging races here, you really >> >>>> need to examine the return value from the wait call. >> >>>> >> >>>>> Speaking of there is a race between state manager thread returning >> >>>>> used delegations and new open. Previously I thought it was evict >> >>>>> inode... >> >>>> >> >>>> Is this with commit 5e99b532bb95 ("nfs4: reset states to use >> >>>> open_stateid when returning delegation voluntarily") applied? >> >>> >> >>> No I have not. I will try that. Thanks. >> >> >> >> This patch does not help. The race is still present. >> > >> > OK. So what are the symptoms? I'm having trouble seeing how a race can >> > happen, given a correctly coded server. >> >> Here's what the server sees: >> open (foobar) replies back with a delegation >> various operations including a close() >> some time goes by... >> open (foobar) replies back with the same delegation > > Why? Olga, we already had this discussion. That sort of server > behaviour is never going to work without races and is the root cause > of your problem. We simply won't ever support servers that do this. Given that there is nothing in the spec about this situation, I think it's not clear that server is acting incorrectly. Do you think it is not possible to fix the client such that open/delegreturn race is happening? Isn't VFS layer achieving the same thing by synchronizing their evict inode code with the new opens? > >> delegreturn >> read (foobar) using delegation -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Trond Myklebust <trond.myklebust@primarydata.com> writes: >> > OK. So what are the symptoms? I'm having trouble seeing how a race can >> > happen, given a correctly coded server. >> >> Here's what the server sees: >> open (foobar) replies back with a delegation >> various operations including a close() >> some time goes by... >> open (foobar) replies back with the same delegation > > Why? Olga, we already had this discussion. That sort of server > behaviour is never going to work without races and is the root cause > of your problem. We simply won't ever support servers that do this. Trond, Specifically, what would the correct behavior be here? Thanks, Andy
On Tue, Oct 13, 2015 at 1:54 PM, Olga Kornievskaia <aglo@umich.edu> wrote: > On Tue, Oct 13, 2015 at 1:28 PM, Trond Myklebust > <trond.myklebust@primarydata.com> wrote: >> On Tue, Oct 13, 2015 at 1:23 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >>> On Tue, Oct 13, 2015 at 12:56 PM, Trond Myklebust >>> <trond.myklebust@primarydata.com> wrote: >>> > On Tue, Oct 13, 2015 at 12:24 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >> On Tue, Oct 13, 2015 at 10:13 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >>> On Tue, Oct 13, 2015 at 9:27 AM, Trond Myklebust >>> >>> <trond.myklebust@primarydata.com> wrote: >>> >>>> On Tue, Oct 13, 2015 at 8:26 AM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >>>>> >>> >>>>> On Mon, Oct 12, 2015 at 11:47 PM, Trond Myklebust >>> >>>>> <trond.myklebust@primarydata.com> wrote: >>> >>>>> > On Mon, Oct 12, 2015 at 5:55 PM, Olga Kornievskaia <aglo@umich.edu> wrote: >>> >>>>> >> It'll be nice to know when we return delegations synchronously or not. >>> >>>>> > >>> >>>>> > Why? This patch forces us to carry an otherwise completely unnecessary >>> >>>>> > parameter, so at the very minimum we should have a discussion of what >>> >>>>> > the real use cases are. >>> >>>>> >>> >>>>> I used it to diagnose the race of open and delegreturn. If it's kept >>> >>>> >>> >>>> How were you using it? >>> >>> >>> >>> I added two more traces points in the beginning of delegreturn and in >>> >>> nfs4_do_open before sending the rpc. I can see that a given file >>> >>> handle: >>> >>> -- delegreturn prepare tracepoint is happening, >>> >>> -- then the tracepoint of before sending the open is logged, >>> >>> -- then delegreturn prepare is logged again, >>> >>> -- then tracepoint for nfs4_open_file which is after receiving reply >>> >>> to the open from the server >>> >>> -- then delegreturn_exit tracepoint >>> >>> >>> >>> kworker/1:0H-14168 [001] .... 576.571636: >>> >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> >>> issync=0 >>> >>> >>> >>> hammer-13955 [000] .... 576.942632: nfs4_open_file_begin: >>> >>> flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:0 >>> >>> fhandle=0x00000000 name=00:2a:904/000002CB.ham >>> >>> >>> >>> hammer-13955 [001] .... 577.043084: nfs4_open_file: >>> >>> error=0 (OK) flags=32768 (0x8000) fmode=READ|0x801c fileid=00:2a:7708 >>> >>> fhandle=0x84792ca9 name=00:2a:904/000002CB.ham >>> >>> >>> >>> kworker/0:1H-431 [000] .... 577.064013: >>> >>> nfs4_delegreturn_prepare: error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> >>> issync=0 >>> >>> >>> >>> kworker/0:1H-431 [000] .... 577.101076: nfs4_delegreturn_exit: >>> >>> error=0 (OK) dev=00:2a fhandle=0x84792ca9 >>> >>> >>> >>> kworker/0:1H-431 [000] .... 577.113021: nfs4_read: >>> >>> error=-10025 (BAD_STATEID) fileid=00:2a:7708 fhandle=0x84792ca9 >>> >>> offset=0 count=64 >>> >>> >>> >>> >>> >>>> >>> >>>>> that some delegreturns are synchronous and others are not I think the >>> >>>>> information is useful. >>> >>>> >>> >>>> The only difference between synchronous and asynchronous in this case >>> >>>> is whether or not the process that launched the delegreturn actually >>> >>>> waits for it to complete; a signal could easily prevent it from doing >>> >>>> so without interrupting the delegreturn call itself. >>> >>>> IOW: for complete information when debugging races here, you really >>> >>>> need to examine the return value from the wait call. >>> >>>> >>> >>>>> Speaking of there is a race between state manager thread returning >>> >>>>> used delegations and new open. Previously I thought it was evict >>> >>>>> inode... >>> >>>> >>> >>>> Is this with commit 5e99b532bb95 ("nfs4: reset states to use >>> >>>> open_stateid when returning delegation voluntarily") applied? >>> >>> >>> >>> No I have not. I will try that. Thanks. >>> >> >>> >> This patch does not help. The race is still present. >>> > >>> > OK. So what are the symptoms? I'm having trouble seeing how a race can >>> > happen, given a correctly coded server. >>> >>> Here's what the server sees: >>> open (foobar) replies back with a delegation >>> various operations including a close() >>> some time goes by... >>> open (foobar) replies back with the same delegation >> >> Why? Olga, we already had this discussion. That sort of server >> behaviour is never going to work without races and is the root cause >> of your problem. We simply won't ever support servers that do this. > > Given that there is nothing in the spec about this situation, I think > it's not clear that server is acting incorrectly. > > Do you think it is not possible to fix the client such that > open/delegreturn race is happening? Isn't VFS layer achieving the same > thing by synchronizing their evict inode code with the new opens? The only 2 ways to prevent this race on the client are: 1) To strictly order _all_ NFSv4 OPENs on the entire filesystem with _all_ DELEGRETURNs on that same filesystem. 2) Alternatively on NFSv4.1+ only, to replace every single OPEN by name RPC call with 2 synchronous RPC calls: one doing a LOOKUP and then a second doing OPEN-by-filehandle after the client has checked whether or not it holds a delegation so that we make sure we can serialise the OPEN and the delegation return. The bottom line is that I'm not going to screw over performance against all other servers on the planet just in order to save someone the bother of typing in the 2-3 lines it would take to check that this delegation was already handed out (and note that the mere existence of a valid stateid on the server is proof of that). -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 13, 2015 at 1:58 PM, Andrew W Elble <aweits@rit.edu> wrote: > > Trond Myklebust <trond.myklebust@primarydata.com> writes: > > >> > OK. So what are the symptoms? I'm having trouble seeing how a race can > >> > happen, given a correctly coded server. > >> > >> Here's what the server sees: > >> open (foobar) replies back with a delegation > >> various operations including a close() > >> some time goes by... > >> open (foobar) replies back with the same delegation > > > > Why? Olga, we already had this discussion. That sort of server > > behaviour is never going to work without races and is the root cause > > of your problem. We simply won't ever support servers that do this. > > Trond, > > Specifically, what would the correct behavior be here? The server should honour the open without repeating the delegation. The client already knows about the delegation due to the first open, so there is no value whatsoever in repeating it. In addition, as you see from Olga's example, it causes races with the return of that delegation. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> The server should honour the open without repeating the delegation. > > The client already knows about the delegation due to the first open, > so there is no value whatsoever in repeating it. In addition, as you > see from Olga's example, it causes races with the return of that > delegation. Thanks for the clarification, I'll be updating my v2 patch to suppress both types of delegations ("duplicate" and "repeated"). Thanks, Andy
On Tue, Oct 13, 2015 at 3:46 PM, Trond Myklebust <trond.myklebust@primarydata.com> wrote: > On Tue, Oct 13, 2015 at 1:58 PM, Andrew W Elble <aweits@rit.edu> wrote: >> >> Trond Myklebust <trond.myklebust@primarydata.com> writes: >> >> >> > OK. So what are the symptoms? I'm having trouble seeing how a race can >> >> > happen, given a correctly coded server. >> >> >> >> Here's what the server sees: >> >> open (foobar) replies back with a delegation >> >> various operations including a close() >> >> some time goes by... >> >> open (foobar) replies back with the same delegation >> > >> > Why? Olga, we already had this discussion. That sort of server >> > behaviour is never going to work without races and is the root cause >> > of your problem. We simply won't ever support servers that do this. >> >> Trond, >> >> Specifically, what would the correct behavior be here? > > The server should honour the open without repeating the delegation. > > The client already knows about the delegation due to the first open, > so there is no value whatsoever in repeating it. In addition, as you > see from Olga's example, it causes races with the return of that > delegation. Trond thank you for the explanations. While I haven't hit the last case of the race I would still like to bring up that we've seen a case where ACCESS is sent and then DELEGRETURN and then delegation stateid is used by the IO. Perhaps the commit 5e99b532bb95 helps in that case. But if not, then this case of the race can't be handled by the server. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Oct 14, 2015 at 10:58 AM, Olga Kornievskaia <aglo@umich.edu> wrote: > On Tue, Oct 13, 2015 at 3:46 PM, Trond Myklebust > <trond.myklebust@primarydata.com> wrote: >> On Tue, Oct 13, 2015 at 1:58 PM, Andrew W Elble <aweits@rit.edu> wrote: >>> >>> Trond Myklebust <trond.myklebust@primarydata.com> writes: >>> >>> >> > OK. So what are the symptoms? I'm having trouble seeing how a race can >>> >> > happen, given a correctly coded server. >>> >> >>> >> Here's what the server sees: >>> >> open (foobar) replies back with a delegation >>> >> various operations including a close() >>> >> some time goes by... >>> >> open (foobar) replies back with the same delegation >>> > >>> > Why? Olga, we already had this discussion. That sort of server >>> > behaviour is never going to work without races and is the root cause >>> > of your problem. We simply won't ever support servers that do this. >>> >>> Trond, >>> >>> Specifically, what would the correct behavior be here? >> >> The server should honour the open without repeating the delegation. >> >> The client already knows about the delegation due to the first open, >> so there is no value whatsoever in repeating it. In addition, as you >> see from Olga's example, it causes races with the return of that >> delegation. > > Trond thank you for the explanations. While I haven't hit the last > case of the race I would still like to bring up that we've seen a case > where ACCESS is sent and then DELEGRETURN and then delegation stateid > is used by the IO. Perhaps the commit 5e99b532bb95 helps in that case. > But if not, then this case of the race can't be handled by the server. That's a different bug, and is indeed a client issue. It should be fixed by commit 24311f884189 + 5e99b532bb95. Please let me know if that is not the case. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index f93b9cd..858c780 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -5283,6 +5283,7 @@ struct nfs4_delegreturndata { struct inode *inode; bool roc; u32 roc_barrier; + int issync; }; static void nfs4_delegreturn_done(struct rpc_task *task, void *calldata) @@ -5292,7 +5293,8 @@ static void nfs4_delegreturn_done(struct rpc_task *task, void *calldata) if (!nfs4_sequence_done(task, &data->res.seq_res)) return; - trace_nfs4_delegreturn_exit(&data->args, &data->res, task->tk_status); + trace_nfs4_delegreturn_exit(&data->args, &data->res, task->tk_status, + data->issync); switch (task->tk_status) { case 0: renew_lease(data->res.server, data->timestamp); @@ -5387,6 +5389,7 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co data->inode = nfs_igrab_and_active(inode); if (data->inode) data->roc = nfs4_roc(inode); + data->issync = issync; task_setup_data.callback_data = data; msg.rpc_argp = &data->args; diff --git a/fs/nfs/nfs4trace.h b/fs/nfs/nfs4trace.h index 671cf68..be67e87 100644 --- a/fs/nfs/nfs4trace.h +++ b/fs/nfs/nfs4trace.h @@ -612,29 +612,33 @@ TRACE_EVENT(nfs4_delegreturn_exit, TP_PROTO( const struct nfs4_delegreturnargs *args, const struct nfs4_delegreturnres *res, - int error + int error, + int issync ), - TP_ARGS(args, res, error), + TP_ARGS(args, res, error, issync), TP_STRUCT__entry( __field(dev_t, dev) __field(u32, fhandle) __field(int, error) + __field(int, issync) ), TP_fast_assign( __entry->dev = res->server->s_dev; __entry->fhandle = nfs_fhandle_hash(args->fhandle); __entry->error = error; + __entry->issync = issync; ), TP_printk( - "error=%d (%s) dev=%02x:%02x fhandle=0x%08x", + "error=%d (%s) dev=%02x:%02x fhandle=0x%08x issync=%d", __entry->error, show_nfsv4_errors(__entry->error), MAJOR(__entry->dev), MINOR(__entry->dev), - __entry->fhandle + __entry->fhandle, + __entry->issync ) );