From: Jan Kara Subject: Re: [PATCH 1/4] bdi: Allow block devices to say that they require stable page writes Date: Mon, 17 Dec 2012 10:04:56 +0100 Message-ID: <20121217090456.GE5133@quack.suse.cz> References: <20121213080740.23360.16346.stgit@blackbox.djwong.org> <20121213080747.23360.24302.stgit@blackbox.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: axboe@kernel.dk, lucho@ionkov.net, jack@suse.cz, ericvh@gmail.com, viro@zeniv.linux.org.uk, rminnich@sandia.gov, tytso@mit.edu, martin.petersen@oracle.com, neilb@suse.de, david@fromorbit.com, Zheng Liu , linux-kernel@vger.kernel.org, hch@infradead.org, linux-fsdevel@vger.kernel.org, adilger.kernel@dilger.ca, bharrosh@panasas.com, jlayton@samba.org, v9fs-developer@lists.sourceforge.net, linux-ext4@vger.kernel.org To: "Darrick J. Wong" Return-path: Content-Disposition: inline In-Reply-To: <20121213080747.23360.24302.stgit@blackbox.djwong.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu 13-12-12 00:07:47, Darrick J. Wong wrote: > This creates a per-backing-device flag that tracks whether or not pages must be > held immutable during writeout. Eventually it will be used to waive > wait_for_page_writeback() if nobody requires stable pages. > > Signed-off-by: Darrick J. Wong Looks good. You can add: Reviewed-by: Jan Kara Honza > --- > Documentation/ABI/testing/sysfs-class-bdi | 5 +++++ > block/blk-integrity.c | 4 ++++ > include/linux/backing-dev.h | 6 ++++++ > mm/backing-dev.c | 11 +++++++++++ > 4 files changed, 26 insertions(+) > > > diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi > index 5f50097..d773d56 100644 > --- a/Documentation/ABI/testing/sysfs-class-bdi > +++ b/Documentation/ABI/testing/sysfs-class-bdi > @@ -48,3 +48,8 @@ max_ratio (read-write) > most of the write-back cache. For example in case of an NFS > mount that is prone to get stuck, or a FUSE mount which cannot > be trusted to play fair. > + > +stable_pages_required (read-only) > + > + If set, the backing device requires that all pages comprising a write > + request must not be changed until writeout is complete. > diff --git a/block/blk-integrity.c b/block/blk-integrity.c > index da2a818..dabd221 100644 > --- a/block/blk-integrity.c > +++ b/block/blk-integrity.c > @@ -420,6 +420,8 @@ int blk_integrity_register(struct gendisk *disk, struct blk_integrity *template) > } else > bi->name = bi_unsupported_name; > > + disk->queue->backing_dev_info.capabilities |= BDI_CAP_STABLE_WRITES; > + > return 0; > } > EXPORT_SYMBOL(blk_integrity_register); > @@ -438,6 +440,8 @@ void blk_integrity_unregister(struct gendisk *disk) > if (!disk || !disk->integrity) > return; > > + disk->queue->backing_dev_info.capabilities &= ~BDI_CAP_STABLE_WRITES; > + > bi = disk->integrity; > > kobject_uevent(&bi->kobj, KOBJ_REMOVE); > diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h > index 2a9a9ab..085501f 100644 > --- a/include/linux/backing-dev.h > +++ b/include/linux/backing-dev.h > @@ -253,6 +253,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); > #define BDI_CAP_EXEC_MAP 0x00000040 > #define BDI_CAP_NO_ACCT_WB 0x00000080 > #define BDI_CAP_SWAP_BACKED 0x00000100 > +#define BDI_CAP_STABLE_WRITES 0x00000200 > > #define BDI_CAP_VMFLAGS \ > (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP) > @@ -307,6 +308,11 @@ long wait_iff_congested(struct zone *zone, int sync, long timeout); > int pdflush_proc_obsolete(struct ctl_table *table, int write, > void __user *buffer, size_t *lenp, loff_t *ppos); > > +static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi) > +{ > + return bdi->capabilities & BDI_CAP_STABLE_WRITES; > +} > + > static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi) > { > return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK); > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index d3ca2b3..41733c5 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -221,12 +221,23 @@ static ssize_t max_ratio_store(struct device *dev, > } > BDI_SHOW(max_ratio, bdi->max_ratio) > > +static ssize_t stable_pages_required_show(struct device *dev, > + struct device_attribute *attr, > + char *page) > +{ > + struct backing_dev_info *bdi = dev_get_drvdata(dev); > + > + return snprintf(page, PAGE_SIZE-1, "%d\n", > + bdi_cap_stable_pages_required(bdi) ? 1 : 0); > +} > + > #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store) > > static struct device_attribute bdi_dev_attrs[] = { > __ATTR_RW(read_ahead_kb), > __ATTR_RW(min_ratio), > __ATTR_RW(max_ratio), > + __ATTR_RO(stable_pages_required), > __ATTR_NULL, > }; > > -- Jan Kara SUSE Labs, CR