| Message ID | 20230901155141.249860-1-shikemeng@huaweicloud.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Fixes and cleanups to compaction | expand |
On Fri, Sep 01, 2023 at 11:51:38PM +0800, Kemeng Shi wrote: > In strict mode, we should return 0 if there is any hole in pageblock. If > we successfully isolated pages at beginning at pageblock and then have a > bogus compound_order outside pageblock in next page. We will abort search > loop with blockpfn > end_pfn. Although we will limit blockpfn to end_pfn, > we will treat it as a successful isolation in strict mode as blockpfn is > not < end_pfn and return partial isolated pages. Then > isolate_freepages_range may success unexpectly with hole in isolated > range. > > Fixes: 9fcd6d2e052e ("mm, compaction: skip compound pages by order in free scanner") > Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > --- > mm/compaction.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index a40550a33aee..9ecbfbc695e5 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -626,11 +626,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > if (PageCompound(page)) { > const unsigned int order = compound_order(page); > > - if (likely(order <= MAX_ORDER)) { > + if (blockpfn + (1UL << order) <= end_pfn) { > blockpfn += (1UL << order) - 1; > page += (1UL << order) - 1; > nr_scanned += (1UL << order) - 1; > } > + > goto isolate_fail; > } > > @@ -678,8 +679,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > spin_unlock_irqrestore(&cc->zone->lock, flags); > > /* > - * There is a tiny chance that we have read bogus compound_order(), > - * so be careful to not go outside of the pageblock. > + * Be careful to not go outside of the pageblock. > */ > if (unlikely(blockpfn > end_pfn)) > blockpfn = end_pfn; Is this check still necessary after the first hunk?
on 9/1/2023 5:17 PM, Mel Gorman wrote: > On Fri, Sep 01, 2023 at 11:51:38PM +0800, Kemeng Shi wrote: >> In strict mode, we should return 0 if there is any hole in pageblock. If >> we successfully isolated pages at beginning at pageblock and then have a >> bogus compound_order outside pageblock in next page. We will abort search >> loop with blockpfn > end_pfn. Although we will limit blockpfn to end_pfn, >> we will treat it as a successful isolation in strict mode as blockpfn is >> not < end_pfn and return partial isolated pages. Then >> isolate_freepages_range may success unexpectly with hole in isolated >> range. >> >> Fixes: 9fcd6d2e052e ("mm, compaction: skip compound pages by order in free scanner") >> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> mm/compaction.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index a40550a33aee..9ecbfbc695e5 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -626,11 +626,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, >> if (PageCompound(page)) { >> const unsigned int order = compound_order(page); >> >> - if (likely(order <= MAX_ORDER)) { >> + if (blockpfn + (1UL << order) <= end_pfn) { >> blockpfn += (1UL << order) - 1; >> page += (1UL << order) - 1; >> nr_scanned += (1UL << order) - 1; >> } >> + >> goto isolate_fail; >> } >> >> @@ -678,8 +679,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, >> spin_unlock_irqrestore(&cc->zone->lock, flags); >> >> /* >> - * There is a tiny chance that we have read bogus compound_order(), >> - * so be careful to not go outside of the pageblock. >> + * Be careful to not go outside of the pageblock. >> */ >> if (unlikely(blockpfn > end_pfn)) >> blockpfn = end_pfn; > > Is this check still necessary after the first hunk? > Actually, I removed this check in the first version, but Baolin thought remove this check is not cheap and not worth it. More discussion can be found in [1]. Thanks! [1] https://lore.kernel.org/all/a8edac8d-8e22-89cf-2c8c-217a54608d27@linux.alibaba.com/
On Fri, Sep 01, 2023 at 05:32:49PM +0800, Kemeng Shi wrote: > > > on 9/1/2023 5:17 PM, Mel Gorman wrote: > > On Fri, Sep 01, 2023 at 11:51:38PM +0800, Kemeng Shi wrote: > >> In strict mode, we should return 0 if there is any hole in pageblock. If > >> we successfully isolated pages at beginning at pageblock and then have a > >> bogus compound_order outside pageblock in next page. We will abort search > >> loop with blockpfn > end_pfn. Although we will limit blockpfn to end_pfn, > >> we will treat it as a successful isolation in strict mode as blockpfn is > >> not < end_pfn and return partial isolated pages. Then > >> isolate_freepages_range may success unexpectly with hole in isolated > >> range. > >> > >> Fixes: 9fcd6d2e052e ("mm, compaction: skip compound pages by order in free scanner") > >> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com> > >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > >> --- > >> mm/compaction.c | 6 +++--- > >> 1 file changed, 3 insertions(+), 3 deletions(-) > >> > >> diff --git a/mm/compaction.c b/mm/compaction.c > >> index a40550a33aee..9ecbfbc695e5 100644 > >> --- a/mm/compaction.c > >> +++ b/mm/compaction.c > >> @@ -626,11 +626,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > >> if (PageCompound(page)) { > >> const unsigned int order = compound_order(page); > >> > >> - if (likely(order <= MAX_ORDER)) { > >> + if (blockpfn + (1UL << order) <= end_pfn) { > >> blockpfn += (1UL << order) - 1; > >> page += (1UL << order) - 1; > >> nr_scanned += (1UL << order) - 1; > >> } > >> + > >> goto isolate_fail; > >> } > >> > >> @@ -678,8 +679,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > >> spin_unlock_irqrestore(&cc->zone->lock, flags); > >> > >> /* > >> - * There is a tiny chance that we have read bogus compound_order(), > >> - * so be careful to not go outside of the pageblock. > >> + * Be careful to not go outside of the pageblock. > >> */ > >> if (unlikely(blockpfn > end_pfn)) > >> blockpfn = end_pfn; > > > > Is this check still necessary after the first hunk? > > > Actually, I removed this check in the first version, but Baolin thought remove this check is not > cheap and not worth it. More discussion can be found in [1]. Thanks! > Ok, fair enough. While I think the check is redundant right now, it's a reasonable defensive check and this is not a fast path so Acked-by: Mel Gorman <mgorman@techsingularity.net>
Hi all, this is another series to do fix and clean up to compaction. Patch 1-2 fix and clean up freepage list operation. Patch 3-4 fix and clean up isolation of freepages Patch 7 factor code to check if compaction is needed for allocation order. More details can be found in respective patches. Thanks! v2->v3: -Collect RVB and ACK from Baolin and Mel -Avoid blockpfn outside pageblock in original likely(order <= MAX_ORDER) block in patch 3 -Move comment into __reset_isolation_suitable in patch 4 -Improve indentation in patch 6 v1->v2: -Collect RVB from Baolin. -Keep pfn inside of pageblock in patch 3. -Only improve comment of is_via_compact_memory in patch 6. -Squash patch 8 and patch 9 into patch 7 and use ALLOC_WMARK_MIN instead of magic number 0. Kemeng Shi (6): mm/compaction: use correct list in move_freelist_{head}/{tail} mm/compaction: call list_is_{first}/{last} more intuitively in move_freelist_{head}/{tail} mm/compaction: correctly return failure with bogus compound_order in strict mode mm/compaction: remove repeat compact_blockskip_flush check in reset_isolation_suitable mm/compaction: improve comment of is_via_compact_memory mm/compaction: factor out code to test if we should run compaction for target order mm/compaction.c | 91 ++++++++++++++++++++++++++++--------------------- 1 file changed, 52 insertions(+), 39 deletions(-)