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+What: /sys/class/bdi/<bdi>/
+Date: January 2008
+Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
+Description:
+
+Provide a place in sysfs for the backing_dev_info object. This allows
+setting and retrieving various BDI specific variables.
+
+The <bdi> identifier can be either of the following:
+
+MAJOR:MINOR
+
+ Device number for block devices, or value of st_dev on
+ non-block filesystems which provide their own BDI, such as NFS
+ and FUSE.
+
+MAJOR:MINOR-fuseblk
+
+ Value of st_dev on fuseblk filesystems.
+
+default
+
+ The default backing dev, used for non-block device backed
+ filesystems which do not provide their own BDI.
+
+What: /sys/class/bdi/<bdi>/read_ahead_kb
+Date: January 2008
+Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
+Description:
+ Size of the read-ahead window in kilobytes
+
+ (read-write)
+What: /sys/class/bdi/<bdi>/min_ratio
+Date: January 2008
+Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
+Description:
+ Under normal circumstances each device is given a part of the
+ total write-back cache that relates to its current average
+ writeout speed in relation to the other devices.
+
+ The 'min_ratio' parameter allows assigning a minimum
+ percentage of the write-back cache to a particular device.
+ For example, this is useful for providing a minimum QoS.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/min_ratio_fine
+Date: November 2022
+Contact: Stefan Roesch <shr@devkernel.io>
+Description:
+ Under normal circumstances each device is given a part of the
+ total write-back cache that relates to its current average
+ writeout speed in relation to the other devices.
+
+ The 'min_ratio_fine' parameter allows assigning a minimum reserve
+ of the write-back cache to a particular device. The value is
+ expressed as part of 1 million. For example, this is useful for
+ providing a minimum QoS.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/max_ratio
+Date: January 2008
+Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
+Description:
+ Allows limiting a particular device to use not more than the
+ given percentage of the write-back cache. This is useful in
+ situations where we want to avoid one device taking all or
+ 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.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/max_ratio_fine
+Date: November 2022
+Contact: Stefan Roesch <shr@devkernel.io>
+Description:
+ Allows limiting a particular device to use not more than the
+ given value of the write-back cache. The value is given as part
+ of 1 million. This is useful in situations where we want to avoid
+ one device taking all or 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.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/min_bytes
+Date: October 2022
+Contact: Stefan Roesch <shr@devkernel.io>
+Description:
+ Under normal circumstances each device is given a part of the
+ total write-back cache that relates to its current average
+ writeout speed in relation to the other devices.
+
+ The 'min_bytes' parameter allows assigning a minimum
+ percentage of the write-back cache to a particular device
+ expressed in bytes.
+ For example, this is useful for providing a minimum QoS.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/max_bytes
+Date: October 2022
+Contact: Stefan Roesch <shr@devkernel.io>
+Description:
+ Allows limiting a particular device to use not more than the
+ given 'max_bytes' of the write-back cache. This is useful in
+ situations where we want to avoid one device taking all or
+ most of the write-back cache. For example in case of an NFS
+ mount that is prone to get stuck, a FUSE mount which cannot be
+ trusted to play fair, or a nbd device.
+
+ (read-write)
+
+What: /sys/class/bdi/<bdi>/strict_limit
+Date: October 2022
+Contact: Stefan Roesch <shr@devkernel.io>
+Description:
+ Forces per-BDI checks for the share of given device in the write-back
+ cache even before the global background dirty limit is reached. This
+ is useful in situations where the global limit is much higher than
+ affordable for given relatively slow (or untrusted) device. Turning
+ strictlimit on has no visible effect if max_ratio is equal to 100%.
+
+ (read-write)
+What: /sys/class/bdi/<bdi>/stable_pages_required
+Date: January 2008
+Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
+Description:
+ If set, the backing device requires that all pages comprising a write
+ request must not be changed until writeout is complete.
+
+ (read-only)