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Subject[PATCH] lightnvm: pblk: limit get chk meta request size
Date
For devices that does not specify a limit on its transfer size, the
get_chk_meta command may send down a single I/O retrieving the full
chunk metadata table. Resulting in large 2-4MB I/O requests. Instead,
split up the I/Os to a maximum of 256KB and issue them separately to
improve I/O latency.

Signed-off-by: Matias Bjørling <mb@lightnvm.io>
---
drivers/nvme/host/lightnvm.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
index b9989717418d..3b644b0e9713 100644
--- a/drivers/nvme/host/lightnvm.c
+++ b/drivers/nvme/host/lightnvm.c
@@ -583,7 +583,13 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev *ndev,
struct ppa_addr ppa;
size_t left = nchks * sizeof(struct nvme_nvm_chk_meta);
size_t log_pos, offset, len;
- int ret, i;
+ int ret, i, max_len;
+
+ /*
+ * limit requests to maximum 256K to avoid issuing arbitrary large
+ * requests when the device does not specific a maximum transfer size.
+ */
+ max_len = min_t(unsigned int, ctrl->max_hw_sectors << 9, 256 * 1024);

/* Normalize lba address space to obtain log offset */
ppa.ppa = slba;
@@ -596,7 +602,7 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev *ndev,
offset = log_pos * sizeof(struct nvme_nvm_chk_meta);

while (left) {
- len = min_t(unsigned int, left, ctrl->max_hw_sectors << 9);
+ len = min_t(unsigned int, left, max_len);

ret = nvme_get_log_ext(ctrl, ns, NVME_NVM_LOG_REPORT_CHUNK,
dev_meta, len, offset);
--
2.11.0
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