4 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index 5f500977b42f..d773d5697cf5 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 da2a818c3a92..dabd221857e1 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 12731a19ef06..350459910fe1 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -254,6 +254,7 @@ 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)
@@ -308,6 +309,11 @@ 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 d3ca2b3ee176..41733c5dc820 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,
 };