| Message ID | 20180928072827.14229-1-jgross@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/blkfront: correct purging of persistent grants | expand |
On Fri, Sep 28, 2018 at 09:28:27AM +0200, Juergen Gross wrote: > Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup > stale persistent grants") introduced a regression as purged persistent > grants were not pu into the list of free grants again. Correct that. s/pu /put / Alan
On 9/28/18 3:28 AM, Juergen Gross wrote: > Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup > stale persistent grants") introduced a regression as purged persistent > grants were not pu into the list of free grants again. Correct that. > > Signed-off-by: Juergen Gross <jgross@suse.com> > --- > drivers/block/xen-blkfront.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index a71d817e900d..429d20131c7e 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) > list_del(&gnt_list_entry->node); > gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); > rinfo->persistent_gnts_c--; > - __free_page(gnt_list_entry->page); > - kfree(gnt_list_entry); > + gnt_list_entry->gref = GRANT_INVALID_REF; > + list_add_tail(&gnt_list_entry->node, &rinfo->grants); Sorry, I don't follow this. What is the purpose of removing the grant from rinfo->grants list with list_del() and then adding it back with list_add_tail()? -boris > } > > spin_unlock_irqrestore(&rinfo->ring_lock, flags);
On 28/09/2018 14:45, Boris Ostrovsky wrote: > On 9/28/18 3:28 AM, Juergen Gross wrote: >> Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup >> stale persistent grants") introduced a regression as purged persistent >> grants were not pu into the list of free grants again. Correct that. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> drivers/block/xen-blkfront.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c >> index a71d817e900d..429d20131c7e 100644 >> --- a/drivers/block/xen-blkfront.c >> +++ b/drivers/block/xen-blkfront.c >> @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) >> list_del(&gnt_list_entry->node); >> gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); >> rinfo->persistent_gnts_c--; >> - __free_page(gnt_list_entry->page); >> - kfree(gnt_list_entry); >> + gnt_list_entry->gref = GRANT_INVALID_REF; >> + list_add_tail(&gnt_list_entry->node, &rinfo->grants); > > Sorry, I don't follow this. What is the purpose of removing the grant > from rinfo->grants list with list_del() and then adding it back with > list_add_tail()? The persistent grants are at the list head and the non-persistent ones at the tail. Juergen
On 9/28/18 9:13 AM, Juergen Gross wrote: > On 28/09/2018 14:45, Boris Ostrovsky wrote: >> On 9/28/18 3:28 AM, Juergen Gross wrote: >>> Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup >>> stale persistent grants") introduced a regression as purged persistent >>> grants were not pu into the list of free grants again. Correct that. >>> >>> Signed-off-by: Juergen Gross <jgross@suse.com> >>> --- >>> drivers/block/xen-blkfront.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c >>> index a71d817e900d..429d20131c7e 100644 >>> --- a/drivers/block/xen-blkfront.c >>> +++ b/drivers/block/xen-blkfront.c >>> @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) >>> list_del(&gnt_list_entry->node); >>> gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); >>> rinfo->persistent_gnts_c--; >>> - __free_page(gnt_list_entry->page); >>> - kfree(gnt_list_entry); >>> + gnt_list_entry->gref = GRANT_INVALID_REF; >>> + list_add_tail(&gnt_list_entry->node, &rinfo->grants); >> Sorry, I don't follow this. What is the purpose of removing the grant >> from rinfo->grants list with list_del() and then adding it back with >> list_add_tail()? > The persistent grants are at the list head and the non-persistent ones > at the tail. Oh, I didn't realize that. But isn't that an optimization (and so not following this rule should not cause errors)? -boris
On 28/09/2018 15:33, Boris Ostrovsky wrote: > On 9/28/18 9:13 AM, Juergen Gross wrote: >> On 28/09/2018 14:45, Boris Ostrovsky wrote: >>> On 9/28/18 3:28 AM, Juergen Gross wrote: >>>> Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup >>>> stale persistent grants") introduced a regression as purged persistent >>>> grants were not pu into the list of free grants again. Correct that. >>>> >>>> Signed-off-by: Juergen Gross <jgross@suse.com> >>>> --- >>>> drivers/block/xen-blkfront.c | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c >>>> index a71d817e900d..429d20131c7e 100644 >>>> --- a/drivers/block/xen-blkfront.c >>>> +++ b/drivers/block/xen-blkfront.c >>>> @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) >>>> list_del(&gnt_list_entry->node); >>>> gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); >>>> rinfo->persistent_gnts_c--; >>>> - __free_page(gnt_list_entry->page); >>>> - kfree(gnt_list_entry); >>>> + gnt_list_entry->gref = GRANT_INVALID_REF; >>>> + list_add_tail(&gnt_list_entry->node, &rinfo->grants); >>> Sorry, I don't follow this. What is the purpose of removing the grant >>> from rinfo->grants list with list_del() and then adding it back with >>> list_add_tail()? >> The persistent grants are at the list head and the non-persistent ones >> at the tail. > > Oh, I didn't realize that. But isn't that an optimization (and so not > following this rule should not cause errors)? In theory: yes. The persistent grant handling is rather complicated so I'd like to make sure not to deviate from the common standards. When I find some time I want to modify the persistent grant handling to be more explicit and controlled completely by the frontend (within the backend defined limits, of course). Until then we should try to modify persistent grants not too much IMO. Juergen
On 9/28/18 9:52 AM, Juergen Gross wrote: > On 28/09/2018 15:33, Boris Ostrovsky wrote: >> On 9/28/18 9:13 AM, Juergen Gross wrote: >>> On 28/09/2018 14:45, Boris Ostrovsky wrote: >>>> On 9/28/18 3:28 AM, Juergen Gross wrote: >>>>> Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup >>>>> stale persistent grants") introduced a regression as purged persistent >>>>> grants were not pu into the list of free grants again. Correct that. >>>>> >>>>> Signed-off-by: Juergen Gross <jgross@suse.com> >>>>> --- >>>>> drivers/block/xen-blkfront.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c >>>>> index a71d817e900d..429d20131c7e 100644 >>>>> --- a/drivers/block/xen-blkfront.c >>>>> +++ b/drivers/block/xen-blkfront.c >>>>> @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) >>>>> list_del(&gnt_list_entry->node); >>>>> gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); >>>>> rinfo->persistent_gnts_c--; >>>>> - __free_page(gnt_list_entry->page); >>>>> - kfree(gnt_list_entry); >>>>> + gnt_list_entry->gref = GRANT_INVALID_REF; >>>>> + list_add_tail(&gnt_list_entry->node, &rinfo->grants); >>>> Sorry, I don't follow this. What is the purpose of removing the grant >>>> from rinfo->grants list with list_del() and then adding it back with >>>> list_add_tail()? >>> The persistent grants are at the list head and the non-persistent ones >>> at the tail. >> Oh, I didn't realize that. But isn't that an optimization (and so not >> following this rule should not cause errors)? > In theory: yes. > > The persistent grant handling is rather complicated so I'd like to make > sure not to deviate from the common standards. I am not arguing with correctness of your patch, so Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> but I am a little surprised that it fixes Sander's problem. -boris > > When I find some time I want to modify the persistent grant handling to > be more explicit and controlled completely by the frontend (within the > backend defined limits, of course). Until then we should try to modify > persistent grants not too much IMO. > > > Juergen
On 9/28/18 1:28 AM, Juergen Gross wrote: > Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup > stale persistent grants") introduced a regression as purged persistent > grants were not pu into the list of free grants again. Correct that. I'll apply this for 4.19, and if things unexpectedly don't work out, we can always revert the series next week.
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index a71d817e900d..429d20131c7e 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2670,8 +2670,8 @@ static void purge_persistent_grants(struct blkfront_info *info) list_del(&gnt_list_entry->node); gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL); rinfo->persistent_gnts_c--; - __free_page(gnt_list_entry->page); - kfree(gnt_list_entry); + gnt_list_entry->gref = GRANT_INVALID_REF; + list_add_tail(&gnt_list_entry->node, &rinfo->grants); } spin_unlock_irqrestore(&rinfo->ring_lock, flags);
Commit a46b53672b2c2e3770b38a4abf90d16364d2584b ("xen/blkfront: cleanup stale persistent grants") introduced a regression as purged persistent grants were not pu into the list of free grants again. Correct that. Signed-off-by: Juergen Gross <jgross@suse.com> --- drivers/block/xen-blkfront.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)