From de881df97768d07b342cbd1f8359b832afccace9 Mon Sep 17 00:00:00 2001 From: Aravind Ramesh Date: Thu, 16 Jul 2020 18:26:56 +0530 Subject: f2fs: support zone capacity less than zone size NVMe Zoned Namespace devices can have zone-capacity less than zone-size. Zone-capacity indicates the maximum number of sectors that are usable in a zone beginning from the first sector of the zone. This makes the sectors sectors after the zone-capacity till zone-size to be unusable. This patch set tracks zone-size and zone-capacity in zoned devices and calculate the usable blocks per segment and usable segments per section. If zone-capacity is less than zone-size mark only those segments which start before zone-capacity as free segments. All segments at and beyond zone-capacity are treated as permanently used segments. In cases where zone-capacity does not align with segment size the last segment will start before zone-capacity and end beyond the zone-capacity of the zone. For such spanning segments only sectors within the zone-capacity are used. During writes and GC manage the usable segments in a section and usable blocks per segment. Segments which are beyond zone-capacity are never allocated, and do not need to be garbage collected, only the segments which are before zone-capacity needs to garbage collected. For spanning segments based on the number of usable blocks in that segment, write to blocks only up to zone-capacity. Zone-capacity is device specific and cannot be configured by the user. Since NVMe ZNS device zones are sequentially write only, a block device with conventional zones or any normal block device is needed along with the ZNS device for the metadata operations of F2fs. A typical nvme-cli output of a zoned device shows zone start and capacity and write pointer as below: SLBA: 0x0 WP: 0x0 Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ SLBA: 0x20000 WP: 0x20000 Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ SLBA: 0x40000 WP: 0x40000 Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ Here zone size is 64MB, capacity is 49MB, WP is at zone start as the zones are in EMPTY state. For each zone, only zone start + 49MB is usable area, any lba/sector after 49MB cannot be read or written to, the drive will fail any attempts to read/write. So, the second zone starts at 64MB and is usable till 113MB (64 + 49) and the range between 113 and 128MB is again unusable. The next zone starts at 128MB, and so on. Signed-off-by: Aravind Ramesh Signed-off-by: Damien Le Moal Signed-off-by: Niklas Cassel Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim --- Documentation/filesystems/f2fs.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'Documentation/filesystems/f2fs.rst') diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index ec8d99703ecb..0f37c7443d5c 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -772,3 +772,18 @@ Compress metadata layout:: +-------------+-------------+----------+----------------------------+ | data length | data chksum | reserved | compressed data | +-------------+-------------+----------+----------------------------+ + +NVMe Zoned Namespace devices +---------------------------- + +- ZNS defines a per-zone capacity which can be equal or less than the + zone-size. Zone-capacity is the number of usable blocks in the zone. + F2fs checks if zone-capacity is less than zone-size, if it is, then any + segment which starts after the zone-capacity is marked as not-free in + the free segment bitmap at initial mount time. These segments are marked + as permanently used so they are not allocated for writes and + consequently are not needed to be garbage collected. In case the + zone-capacity is not aligned to default segment size(2MB), then a segment + can start before the zone-capacity and span across zone-capacity boundary. + Such spanning segments are also considered as usable segments. All blocks + past the zone-capacity are considered unusable in these segments. -- cgit v1.2.3