This creates a per-backing-device counter that tracks the number of users which
require pages to 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>
---
Documentation/ABI/testing/sysfs-class-bdi | 7 +++++
block/blk-integrity.c | 4 +++
include/linux/backing-dev.h | 16 ++++++++++++
include/linux/blkdev.h | 10 ++++++++
mm/backing-dev.c | 38 +++++++++++++++++++++++++++++
5 files changed, 75 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index 5f50097..218a618 100644
--- a/Documentation/ABI/testing/sysfs-class-bdi
+++ b/Documentation/ABI/testing/sysfs-class-bdi
@@ -48,3 +48,10 @@ 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-write)
+
+ If set, the backing device requires that all pages comprising a write
+ request must not be changed until writeout is complete. The system
+ administrator can turn this on if the hardware does not do so already.
+ However, once enabled, this flag cannot be disabled.
diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index da2a818..cf2dd95 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;
+ queue_require_stable_pages(disk->queue);
+
return 0;
}
EXPORT_SYMBOL(blk_integrity_register);
@@ -438,6 +440,8 @@ void blk_integrity_unregister(struct gendisk *disk)
if (!disk || !disk->integrity)
return;
+ queue_unrequire_stable_pages(disk->queue);
+
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..0554f5d 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -109,6 +109,7 @@ struct backing_dev_info {
struct dentry *debug_dir;
struct dentry *debug_stats;
#endif
+ atomic_t stable_page_users;
};
int bdi_init(struct backing_dev_info *bdi);
@@ -307,6 +308,21 @@ 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 void bdi_require_stable_pages(struct backing_dev_info *bdi)
+{
+ atomic_inc(&bdi->stable_page_users);
+}
+
+static inline void bdi_unrequire_stable_pages(struct backing_dev_info *bdi)
+{
+ atomic_dec(&bdi->stable_page_users);
+}
+
+static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
+{
+ return atomic_read(&bdi->stable_page_users) > 0;
+}
+
static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
{
return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1756001..bf927c0 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -458,6 +458,16 @@ struct request_queue {
(1 << QUEUE_FLAG_SAME_COMP) | \
(1 << QUEUE_FLAG_ADD_RANDOM))
+static inline void queue_require_stable_pages(struct request_queue *q)
+{
+ bdi_require_stable_pages(&q->backing_dev_info);
+}
+
+static inline void queue_unrequire_stable_pages(struct request_queue *q)
+{
+ bdi_unrequire_stable_pages(&q->backing_dev_info);
+}
+
static inline void queue_lockdep_assert_held(struct request_queue *q)
{
if (q->queue_lock)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index d3ca2b3..dd9f5ed 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -221,12 +221,48 @@ static ssize_t max_ratio_store(struct device *dev,
}
BDI_SHOW(max_ratio, bdi->max_ratio)
+static ssize_t stable_pages_required_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ unsigned int spw;
+ ssize_t ret;
+
+ ret = kstrtouint(buf, 10, &spw);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * SPW could be enabled due to hw requirement, so don't
+ * let users disable it.
+ */
+ if (bdi_cap_stable_pages_required(bdi) && spw == 0)
+ return -EINVAL;
+
+ if (spw != 0)
+ atomic_inc(&bdi->stable_page_users);
+
+ return count;
+}
+
+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_RW(stable_pages_required),
__ATTR_NULL,
};
@@ -650,6 +686,8 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->write_bandwidth = INIT_BW;
bdi->avg_write_bandwidth = INIT_BW;
+ atomic_set(&bdi->stable_page_users, 0);
+
err = fprop_local_init_percpu(&bdi->completions);
if (err) {
--
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