On Mon, Oct 1, 2018 at 2:54 PM Alexander Duyck
<alexander.h.duyck@xxxxxxxxxxxxxxx> wrote:
On 10/1/2018 2:14 PM, Dan Williams wrote:
Use kvzalloc() to bypass the arbitrary PAGE_SIZE limit of label transfer
operations. Given the expense of calling into firmware, maximize the
amount of label data we transfer per call to be up to the total label
space if allowed by the firmware, or 256K whichever is smaller.
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Changes in v2:
* clamp the max allocation size at 256K in case large label areas with
unlimited transfer sizes appear in the future.
drivers/nvdimm/dimm_devs.c | 14 ++++++++------
tools/testing/nvdimm/test/nfit.c | 2 +-
2 files changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 863cabc35215..3616e2e47788 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -111,8 +111,9 @@ int nvdimm_init_config_data(struct nvdimm_drvdata *ndd)
if (!ndd->data)
return -ENOMEM;
- max_cmd_size = min_t(u32, PAGE_SIZE, ndd->nsarea.max_xfer);
- cmd = kzalloc(max_cmd_size + sizeof(*cmd), GFP_KERNEL);
+ max_cmd_size = min_t(u32, ndd->nsarea.config_size, SZ_256K);
+ max_cmd_size = min_t(u32, max_cmd_size, ndd->nsarea.max_xfer);
+ cmd = kvzalloc(max_cmd_size + sizeof(*cmd), GFP_KERNEL);
if (!cmd)
return -ENOMEM;
So I wouldn't use 256K as the limit, maybe 256K minus the sizeof(*cmd).
Otherwise you are still allocating additional memory to take care of
that little trailing bit that is being added.
Does it matter? This is a slow / infrequently used path and I do don't
see the practical difference of 256K vs slightly less than 256K.
@@ -134,7 +135,7 @@ int nvdimm_init_config_data(struct nvdimm_drvdata *ndd)
memcpy(ndd->data + offset, cmd->out_buf, cmd->in_length);
}
dev_dbg(ndd->dev, "len: %zu rc: %d\n", offset, rc);
- kfree(cmd);
+ kvfree(cmd);
return rc;
}
@@ -157,9 +158,10 @@ int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
if (offset + len > ndd->nsarea.config_size)
return -ENXIO;
- max_cmd_size = min_t(u32, PAGE_SIZE, len);
+ max_cmd_size = min_t(u32, ndd->nsarea.config_size, SZ_256K);
max_cmd_size = min_t(u32, max_cmd_size, ndd->nsarea.max_xfer);
- cmd = kzalloc(max_cmd_size + sizeof(*cmd) + sizeof(u32), GFP_KERNEL);
+ max_cmd_size = min_t(u32, max_cmd_size, len);
+ cmd = kvzalloc(max_cmd_size + sizeof(*cmd) + sizeof(u32), GFP_KERNEL);
if (!cmd)
return -ENOMEM;
For the set operation I am not sure you have any code that is going to
be updating things multiple labels at a time. From what I can tell the
largest set call you ever make is probably for a namespace index and
odds are that will only ever be 256 or 512 bytes.
Inside the kernel, true, but we do perform large sets from userspace.
That said I don't see why this low level routine should encode
layering violation knowledge of how it might be used.
Also the limitations here could probably use some additional clean-up.
For example you have a check for offset + len > config_size above this
min_t calls. As such it should be impossible for length to ever be
greater than config_size so you shouldn't need to test for the min of
both and could just use the min of len versus the max_xfer.
Again that's a case of this leaf routine encoding assumptions about
how it might be used. I'd rather be pedantic since this is not a hot
path.