lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <20130116020000.GA25806@quack.suse.cz> Date: Wed, 16 Jan 2013 03:00:00 +0100 From: Jan Kara <jack@...e.cz> To: "Darrick J. Wong" <darrick.wong@...cle.com> Cc: axboe@...nel.dk, lucho@...kov.net, jack@...e.cz, ericvh@...il.com, tytso@....edu, viro@...iv.linux.org.uk, rminnich@...dia.gov, martin.petersen@...cle.com, neilb@...e.de, david@...morbit.com, gnehzuil.liu@...il.com, linux-kernel@...r.kernel.org, hch@...radead.org, linux-fsdevel@...r.kernel.org, Andy Lutomirski <luto@...capital.net>, adilger.kernel@...ger.ca, bharrosh@...asas.com, jlayton@...ba.org, linux-ext4@...r.kernel.org, hirofumi@...l.parknet.co.jp Subject: Re: [PATCH 4/6] block: Optionally snapshot page contents to provide stable pages during write On Mon 14-01-13 21:43:05, Darrick J. Wong wrote: > This provides a band-aid to provide stable page writes on jbd without needing > to backport the fixed locking and page writeback bit handling schemes of jbd2. > The band-aid works by using bounce buffers to snapshot page contents instead of > waiting. > > For those wondering about the ext3 bandage -- fixing the jbd locking (which was > done as part of ext4dev years ago) is a lot of surgery, and setting > PG_writeback on data pages when we actually hold the page lock dropped ext3 > performance by nearly an order of magnitude. If we're going to migrate iscsi > and raid to use stable page writes, the complaints about high latency will > likely return. We might as well centralize their page snapshotting thing to > one place. > > Tested-by: Andy Lutomirski <luto@...capital.net> > Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com> > --- > arch/tile/Kconfig | 6 ------ > block/blk-core.c | 8 +++++--- > fs/ext3/super.c | 1 + > include/uapi/linux/fs.h | 1 + > mm/Kconfig | 13 +++++++++++++ > mm/bounce.c | 47 +++++++++++++++++++++++++++++++++++++++++++---- > mm/page-writeback.c | 4 ++++ > 7 files changed, 67 insertions(+), 13 deletions(-) > > > diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig > index 875d008..c671fda 100644 > --- a/arch/tile/Kconfig > +++ b/arch/tile/Kconfig > @@ -410,12 +410,6 @@ config TILE_USB > Provides USB host adapter support for the built-in EHCI and OHCI > interfaces on TILE-Gx chips. > > -# USB OHCI needs the bounce pool since tilegx will often have more > -# than 4GB of memory, but we don't currently use the IOTLB to present > -# a 32-bit address to OHCI. So we need to use a bounce pool instead. > -config NEED_BOUNCE_POOL > - def_bool USB_OHCI_HCD > - > source "drivers/pci/hotplug/Kconfig" > > endmenu > diff --git a/block/blk-core.c b/block/blk-core.c > index c973249..277134c 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1474,6 +1474,11 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio) > */ > blk_queue_bounce(q, &bio); > > + if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) { > + bio_endio(bio, -EIO); > + return; > + } > + > if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) { > spin_lock_irq(q->queue_lock); > where = ELEVATOR_INSERT_FLUSH; > @@ -1714,9 +1719,6 @@ generic_make_request_checks(struct bio *bio) > */ > blk_partition_remap(bio); > > - if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) > - goto end_io; > - Umm, why did you move this hunk? > if (bio_check_eod(bio, nr_sectors)) > goto end_io; > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index 780d4c6..0144fbb 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -69,6 +69,7 @@ struct inodes_stat_t { > #define MS_REMOUNT 32 /* Alter flags of a mounted FS */ > #define MS_MANDLOCK 64 /* Allow mandatory locks on an FS */ > #define MS_DIRSYNC 128 /* Directory modifications are synchronous */ > +#define MS_SNAP_STABLE 256 /* Snapshot pages during writeback, if needed */ > #define MS_NOATIME 1024 /* Do not update access times. */ > #define MS_NODIRATIME 2048 /* Do not update directory access times */ > #define MS_BIND 4096 Please don't mix MS_SNAP_STABLE flag among flags passed by mount(2) syscall. I think putting it at 1 << 27 might be acceptable. I remember Al Viro saying something along the lines that kernel internal superblock flags should be separated from those passed from userspace into a special superblock entry but that's a different story I guess. > diff --git a/mm/Kconfig b/mm/Kconfig > index 278e3ab..7901d83 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -258,6 +258,19 @@ config BOUNCE > def_bool y > depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) > > +# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often > +# have more than 4GB of memory, but we don't currently use the IOTLB to present > +# a 32-bit address to OHCI. So we need to use a bounce pool instead. > +# > +# We also use the bounce pool to provide stable page writes for jbd. jbd > +# initiates buffer writeback without locking the page or setting PG_writeback, > +# and fixing that behavior (a second time; jbd2 doesn't have this problem) is > +# a major rework effort. Instead, use the bounce buffer to snapshot pages > +# (until jbd goes away). The only jbd user is ext3. > +config NEED_BOUNCE_POOL > + bool > + default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) > + > config NR_QUICK > int > depends on QUICKLIST > diff --git a/mm/bounce.c b/mm/bounce.c > index 0420867..a5b30f9 100644 > --- a/mm/bounce.c > +++ b/mm/bounce.c > @@ -178,8 +178,44 @@ static void bounce_end_io_read_isa(struct bio *bio, int err) > __bounce_end_io_read(bio, isa_page_pool, err); > } > > +#ifdef CONFIG_NEED_BOUNCE_POOL > +static int must_snapshot_stable_pages(struct bio *bio) > +{ > + struct page *page; > + struct backing_dev_info *bdi; > + struct address_space *mapping; > + struct bio_vec *from; > + int i; > + > + if (bio_data_dir(bio) != WRITE) > + return 0; > + > + /* > + * Based on the first page that has a valid mapping, decide whether or > + * not we have to employ bounce buffering to guarantee stable pages. > + */ > + bio_for_each_segment(from, bio, i) { > + page = from->bv_page; > + mapping = page_mapping(page); > + if (!mapping) > + continue; > + bdi = mapping->backing_dev_info; > + if (!bdi_cap_stable_pages_required(bdi)) > + return 0; > + return mapping->host->i_sb->s_flags & MS_SNAP_STABLE; > + } > + > + return 0; > +} How about using q->backing_dev_info for the bdi_cap_stable_pages_required() check? It will be a fast path and this check will be faster.. Honza -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists