nbd: implement the WRITE_ZEROES command

The NBD protocol defines a message for zeroing out a region of an export

Add support to the kernel driver for that message.

Signed-off-by: Wouter Verhelst <w@uter.be>
Cc: Eric Blake <eblake@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240812133032.115134-3-w@uter.be
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 4d06472bf11228312812032ce0608f2e544589f1..eee632b84994f7f650bf9d09216462119fdcd3e8 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -363,6 +363,8 @@ static int __nbd_set_size(struct nbd_device *nbd, loff_t bytesize,
        }
        if (nbd->config->flags & NBD_FLAG_ROTATIONAL)
                lim.features |= BLK_FEAT_ROTATIONAL;
+       if (nbd->config->flags & NBD_FLAG_SEND_WRITE_ZEROES)
+               lim.max_write_zeroes_sectors = UINT_MAX >> SECTOR_SHIFT;
 
        lim.logical_block_size = blksize;
        lim.physical_block_size = blksize;
@@ -432,6 +434,8 @@ static u32 req_to_nbd_cmd_type(struct request *req)
                return NBD_CMD_WRITE;
        case REQ_OP_READ:
                return NBD_CMD_READ;
+       case REQ_OP_WRITE_ZEROES:
+               return NBD_CMD_WRITE_ZEROES;
        default:
                return U32_MAX;
        }
@@ -648,6 +652,8 @@ static blk_status_t nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
 
        if (req->cmd_flags & REQ_FUA)
                nbd_cmd_flags |= NBD_CMD_FLAG_FUA;
+       if ((req->cmd_flags & REQ_NOUNMAP) && (type == NBD_CMD_WRITE_ZEROES))
+               nbd_cmd_flags |= NBD_CMD_FLAG_NO_HOLE;
 
        /* We did a partial send previously, and we at least sent the whole
         * request struct, so just go and send the rest of the pages in the
@@ -1717,6 +1723,8 @@ static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
                seq_puts(s, "NBD_FLAG_SEND_FUA\n");
        if (flags & NBD_FLAG_SEND_TRIM)
                seq_puts(s, "NBD_FLAG_SEND_TRIM\n");
+       if (flags & NBD_FLAG_SEND_WRITE_ZEROES)
+               seq_puts(s, "NBD_FLAG_SEND_WRITE_ZEROES\n");
 
        return 0;
 }

diff --git a/include/uapi/linux/nbd.h b/include/uapi/linux/nbd.h
index d75215f2c675340c0ed00817b3dbd743e8c17e7a..f1d468acfb2530c871d9d3793fc9e6b8fbb22056 100644 (file)
--- a/include/uapi/linux/nbd.h
+++ b/include/uapi/linux/nbd.h
@@ -42,8 +42,9 @@ enum {
        NBD_CMD_WRITE = 1,
        NBD_CMD_DISC = 2,
        NBD_CMD_FLUSH = 3,
-       NBD_CMD_TRIM = 4
+       NBD_CMD_TRIM = 4,
        /* userspace defines additional extension commands */
+       NBD_CMD_WRITE_ZEROES = 6,
 };
 
 /* values for flags field, these are server interaction specific. */
@@ -53,11 +54,13 @@ enum {
 #define NBD_FLAG_SEND_FUA      (1 << 3) /* send FUA (forced unit access) */
 #define NBD_FLAG_ROTATIONAL    (1 << 4) /* device is rotational */
 #define NBD_FLAG_SEND_TRIM     (1 << 5) /* send trim/discard */
+#define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* supports WRITE_ZEROES */
 /* there is a gap here to match userspace */
 #define NBD_FLAG_CAN_MULTI_CONN        (1 << 8)        /* Server supports multiple connections per export. */
 
 /* values for cmd flags in the upper 16 bits of request type */
 #define NBD_CMD_FLAG_FUA       (1 << 16) /* FUA (forced unit access) op */
+#define NBD_CMD_FLAG_NO_HOLE   (1 << 17) /* Do not punch a hole for WRITE_ZEROES */
 
 /* These are client behavior specific flags. */
 #define NBD_CFLAG_DESTROY_ON_DISCONNECT        (1 << 0) /* delete the nbd device on