| Message ID | 20240803130432.5952-1-w@uter.be (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] nbd: implement the WRITE_ZEROES command | expand |
On Sat, Aug 03, 2024 at 03:04:30PM GMT, Wouter Verhelst wrote: > 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> > --- > drivers/block/nbd.c | 8 ++++++++ > include/uapi/linux/nbd.h | 5 ++++- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index 5b1811b1ba5f..215e7ea9a3c3 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -352,6 +352,8 @@ 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; Is that number accurate, when the kernel has not yet been taught to use 64-bit transactions and can therefore only request a 32-bit byte length on any one transaction? Would a better limit be UINT_MAX/blksize?
On Mon, Aug 05, 2024 at 07:52:42AM -0500, Eric Blake wrote: > On Sat, Aug 03, 2024 at 03:04:30PM GMT, Wouter Verhelst wrote: > > 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> > > --- > > drivers/block/nbd.c | 8 ++++++++ > > include/uapi/linux/nbd.h | 5 ++++- > > 2 files changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > > index 5b1811b1ba5f..215e7ea9a3c3 100644 > > --- a/drivers/block/nbd.c > > +++ b/drivers/block/nbd.c > > @@ -352,6 +352,8 @@ 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; > > Is that number accurate, when the kernel has not yet been taught to > use 64-bit transactions and can therefore only request a 32-bit byte > length on any one transaction? Would a better limit be > UINT_MAX/blksize? Thanks, good catch. I copied the logic from the handling of the TRIM command (i.e., the discard logic), which has the same flawed UINT_MAX behavior. I will fix this in v2 and add a fix for the discard code.
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 5b1811b1ba5f..215e7ea9a3c3 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -352,6 +352,8 @@ 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; lim.logical_block_size = blksize; lim.physical_block_size = blksize; @@ -421,6 +423,8 @@ 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; } @@ -637,6 +641,8 @@ 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 @@ -1706,6 +1712,8 @@ 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 d75215f2c675..f1d468acfb25 100644 --- 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
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> --- drivers/block/nbd.c | 8 ++++++++ include/uapi/linux/nbd.h | 5 ++++- 2 files changed, 12 insertions(+), 1 deletion(-)