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 <darrick.wong@xxxxxxxxxx>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
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 <jack@xxxxxxx>
SUSE Labs, CR
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