[PATCH v3 02/24] NFSv4/flexfiles: Use the full 64-bit stripe_unit

[Benjamin Coddington <ben.coddington@hammerspace.com>]

ff_layout_alloc_lseg() decodes stripe_unit as the 64-bit value the
protocol defines and struct nfs4_ff_layout_segment stores it as one, but
both consumers narrow it back to 32 bits: nfs4_ff_layout_calc_dss_id()
divides with do_div(), which casts the divisor, and ff_layout_pg_test()
copies it into a u32 first.  A stripe_unit that does not fit is silently
truncated, so the client stripes on a unit the server did not specify --
or divides by zero, if the low 32 bits happen to be clear.

Divide by the full value, with div64_u64() and div64_u64_rem().

Fixes: 20b1d75fb840 ("NFSv4/flexfiles: Add support for striped layouts")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 12 ++++++------
 fs/nfs/flexfilelayout/flexfilelayout.h |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 7fe8b91fa47c..54ee8f6051ee 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -995,9 +995,9 @@ ff_layout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 {
 	unsigned int size;
 	u64 p_stripe, r_stripe;
-	u32 stripe_offset;
+	u64 stripe_offset;
 	u64 segment_offset = pgio->pg_lseg->pls_range.offset;
-	u32 stripe_unit = FF_LAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;
+	u64 stripe_unit = FF_LAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;
 
 	/* calls nfs_generic_pg_test */
 	size = pnfs_generic_pg_test(pgio, prev, req);
@@ -1010,21 +1010,21 @@ ff_layout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
 	if (prev) {
 		p_stripe = (u64)req_offset(prev) - segment_offset;
 		r_stripe = (u64)req_offset(req) - segment_offset;
-		do_div(p_stripe, stripe_unit);
-		do_div(r_stripe, stripe_unit);
+		p_stripe = div64_u64(p_stripe, stripe_unit);
+		r_stripe = div64_u64(r_stripe, stripe_unit);
 
 		if (p_stripe != r_stripe)
 			return 0;
 	}
 
 	/* calculate remaining bytes in the current stripe */
-	div_u64_rem((u64)req_offset(req) - segment_offset,
+	div64_u64_rem((u64)req_offset(req) - segment_offset,
 			stripe_unit,
 			&stripe_offset);
 	WARN_ON_ONCE(stripe_offset > stripe_unit);
 	if (stripe_offset >= stripe_unit)
 		return 0;
-	return min(stripe_unit - (unsigned int)stripe_offset, size);
+	return min_t(u64, stripe_unit - stripe_offset, size);
 }
 
 static void
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index a5bd00f69e82..ec69cd1c3ae9 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -220,7 +220,7 @@ nfs4_ff_layout_calc_dss_id(const u64 stripe_unit, const u32 dss_count, const lof
 	if (dss_count == 1 || stripe_unit == 0)
 		return 0;
 
-	do_div(tmp, stripe_unit);
+	tmp = div64_u64(tmp, stripe_unit);
 
 	return do_div(tmp, dss_count);
 }
-- 
2.53.0