From: Danish Khateeb <danishkhateeb03@gmail.com>
To: "Martin K. Petersen" <mkp@kernel.org>
Cc: linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Akinobu Mita <akinobu.mita@gmail.com>,
Danish Khateeb <danishkhateeb03@gmail.com>
Subject: [PATCH 2/2] scsi: target: core: Use kmap_local_page() in SBC emulation
Date: Wed, 23 Sep 2026 08:13:19 -0500 [thread overview]
Message-ID: <20260923131319.310123-3-danishkhateeb03@gmail.com> (raw)
In-Reply-To: <20260923131319.310123-1-danishkhateeb03@gmail.com>
kmap_atomic() is deprecated in favour of kmap_local_page(). Convert the
kmap_atomic() and kunmap_atomic() calls in sbc_dif_generate(),
sbc_dif_verify(), sbc_dif_copy_prot() and compare_and_write_do_cmp().
The mappings already nest the way kmap_local_page() requires. The
protection page is mapped first and unmapped last, and the data page (the
rd protection page in sbc_dif_copy_prot()) is mapped and unmapped inside
it, including on the early returns. compare_and_write_do_cmp() maps one
page at a time. The code between map and unmap only works on kernel
memory with memcpy(), memcmp(), the CRC helpers and pr_*(), so it does
not rely on page faults or preemption being disabled.
Apart from dropping the deprecated calls, this lets preemptible kernels
preempt the guard tag CRCs in sbc_dif_generate() and sbc_dif_verify(),
which run inside the mapping of a protection SGL entry: up to 512 blocks
per page of protection information, 2 MiB of data with 4 KiB blocks.
Assisted-by: LLM
Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>
---
drivers/target/target_core_sbc.c | 56 ++++++++++++++++----------------
1 file changed, 28 insertions(+), 28 deletions(-)
diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 55a8c2f0a286..2c79bca5f6e4 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -406,7 +406,7 @@ compare_and_write_do_cmp(struct scatterlist *read_sgl, unsigned int read_nents,
ret = TCM_NO_SENSE;
for_each_sg(read_sgl, sg, read_nents, sg_cnt) {
unsigned int len = min(sg->length, cmp_len);
- unsigned char *addr = kmap_atomic(sg_page(sg));
+ unsigned char *addr = kmap_local_page(sg_page(sg));
if (memcmp(addr, buf + offset, len)) {
unsigned int i;
@@ -418,7 +418,7 @@ compare_and_write_do_cmp(struct scatterlist *read_sgl, unsigned int read_nents,
*miscmp_off);
ret = TCM_MISCOMPARE_VERIFY;
}
- kunmap_atomic(addr);
+ kunmap_local(addr);
if (ret != TCM_NO_SENSE)
goto out;
@@ -1222,8 +1222,8 @@ sbc_dif_generate(struct se_cmd *cmd)
unsigned int block_size = dev->dev_attrib.block_size;
for_each_sg(cmd->t_prot_sg, psg, cmd->t_prot_nents, i) {
- paddr = kmap_atomic(sg_page(psg)) + psg->offset;
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ paddr = kmap_local_page(sg_page(psg)) + psg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
for (j = 0; j < psg->length;
j += sizeof(*sdt)) {
@@ -1232,26 +1232,26 @@ sbc_dif_generate(struct se_cmd *cmd)
if (offset >= dsg->length) {
offset -= dsg->length;
- kunmap_atomic(daddr - dsg->offset);
+ kunmap_local(daddr - dsg->offset);
dsg = sg_next(dsg);
if (!dsg) {
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(paddr - psg->offset);
return;
}
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
}
sdt = paddr + j;
avail = min(block_size, dsg->length - offset);
crc = crc_t10dif(daddr + offset, avail);
if (avail < block_size) {
- kunmap_atomic(daddr - dsg->offset);
+ kunmap_local(daddr - dsg->offset);
dsg = sg_next(dsg);
if (!dsg) {
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(paddr - psg->offset);
return;
}
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
offset = block_size - avail;
crc = crc_t10dif_update(crc, daddr, offset);
} else {
@@ -1273,8 +1273,8 @@ sbc_dif_generate(struct se_cmd *cmd)
sector++;
}
- kunmap_atomic(daddr - dsg->offset);
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(daddr - dsg->offset);
+ kunmap_local(paddr - psg->offset);
}
}
@@ -1336,18 +1336,18 @@ void sbc_dif_copy_prot(struct se_cmd *cmd, unsigned int sectors, bool read,
for_each_sg(cmd->t_prot_sg, psg, cmd->t_prot_nents, i) {
unsigned int psg_len, copied = 0;
- paddr = kmap_atomic(sg_page(psg)) + psg->offset;
+ paddr = kmap_local_page(sg_page(psg)) + psg->offset;
psg_len = min(left, psg->length);
while (psg_len) {
len = min(psg_len, sg->length - offset);
- addr = kmap_atomic(sg_page(sg)) + sg->offset + offset;
+ addr = kmap_local_page(sg_page(sg)) + sg->offset + offset;
if (read)
memcpy(paddr + copied, addr, len);
else
memcpy(addr, paddr + copied, len);
- kunmap_atomic(addr - sg->offset - offset);
+ kunmap_local(addr - sg->offset - offset);
left -= len;
offset += len;
@@ -1359,7 +1359,7 @@ void sbc_dif_copy_prot(struct se_cmd *cmd, unsigned int sectors, bool read,
offset = 0;
}
}
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(paddr - psg->offset);
}
}
EXPORT_SYMBOL(sbc_dif_copy_prot);
@@ -1379,8 +1379,8 @@ sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
unsigned int block_size = dev->dev_attrib.block_size;
for (; psg && sector < start + sectors; psg = sg_next(psg)) {
- paddr = kmap_atomic(sg_page(psg)) + psg->offset;
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ paddr = kmap_local_page(sg_page(psg)) + psg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
for (i = psg_off; i < psg->length &&
sector < start + sectors;
@@ -1390,13 +1390,13 @@ sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
if (dsg_off >= dsg->length) {
dsg_off -= dsg->length;
- kunmap_atomic(daddr - dsg->offset);
+ kunmap_local(daddr - dsg->offset);
dsg = sg_next(dsg);
if (!dsg) {
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(paddr - psg->offset);
return 0;
}
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
}
sdt = paddr + i;
@@ -1414,13 +1414,13 @@ sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
avail = min(block_size, dsg->length - dsg_off);
crc = crc_t10dif(daddr + dsg_off, avail);
if (avail < block_size) {
- kunmap_atomic(daddr - dsg->offset);
+ kunmap_local(daddr - dsg->offset);
dsg = sg_next(dsg);
if (!dsg) {
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(paddr - psg->offset);
return 0;
}
- daddr = kmap_atomic(sg_page(dsg)) + dsg->offset;
+ daddr = kmap_local_page(sg_page(dsg)) + dsg->offset;
dsg_off = block_size - avail;
crc = crc_t10dif_update(crc, daddr, dsg_off);
} else {
@@ -1429,8 +1429,8 @@ sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
rc = sbc_dif_v1_verify(cmd, sdt, crc, sector, ei_lba);
if (rc) {
- kunmap_atomic(daddr - dsg->offset);
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(daddr - dsg->offset);
+ kunmap_local(paddr - psg->offset);
cmd->sense_info = sector;
return rc;
}
@@ -1440,8 +1440,8 @@ sbc_dif_verify(struct se_cmd *cmd, sector_t start, unsigned int sectors,
}
psg_off = 0;
- kunmap_atomic(daddr - dsg->offset);
- kunmap_atomic(paddr - psg->offset);
+ kunmap_local(daddr - dsg->offset);
+ kunmap_local(paddr - psg->offset);
}
return 0;
--
2.55.0
prev parent reply other threads:[~2026-09-23 13:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-23 13:13 [PATCH 0/2] scsi: target: core: Fix and convert kmap_atomic() " Danish Khateeb
2026-09-23 13:13 ` [PATCH 1/2] scsi: target: core: Fix kunmap_atomic() address in sbc_dif_copy_prot() Danish Khateeb
2026-09-23 13:13 ` Danish Khateeb [this message]
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