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nbd: implement the WRITE_ZEROES command

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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>
This commit is contained in:
Wouter Verhelst
2024-08-12 15:20:37 +02:00
committed by Jens Axboe
parent f55d3b82ac
commit e49dacc71e
2 changed files with 12 additions and 1 deletions
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include/uapi/linux/nbd.h
+4 -1
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@@ -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