bcache: fix a spurious gcc complaint, use scnprintf

An old version of gcc was complaining about using a const int as the
size of a stack allocated array. Which should be fine - but using
ARRAY_SIZE() is better, anyways.

Also, refactor the code to use scnprintf().

Signed-off-by: Kent Overstreet <koverstreet@google.com>

1 files changed, 22 insertions, 21 deletions

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 4d9cca47e4c6..29228b8a6ffe 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -665,12 +665,10 @@ SHOW(__bch_cache)
                 int cmp(const void *l, const void *r)
                 {       return *((uint16_t *) r) - *((uint16_t *) l); }
 
-                /* Number of quantiles we compute */
-                const unsigned nq = 31;
-
                 size_t n = ca->sb.nbuckets, i, unused, btree;
                 uint64_t sum = 0;
-                uint16_t q[nq], *p, *cached;
+                /* Compute 31 quantiles */
+                uint16_t q[31], *p, *cached;
                 ssize_t ret;
 
                 cached = p = vmalloc(ca->sb.nbuckets * sizeof(uint16_t));
@@ -703,26 +701,29 @@ SHOW(__bch_cache)
                 if (n)
                         do_div(sum, n);
 
-                for (i = 0; i < nq; i++)
-                        q[i] = INITIAL_PRIO - cached[n * (i + 1) / (nq + 1)];
+                for (i = 0; i < ARRAY_SIZE(q); i++)
+                        q[i] = INITIAL_PRIO - cached[n * (i + 1) /
+                                (ARRAY_SIZE(q) + 1)];
 
                 vfree(p);
 
-                ret = snprintf(buf, PAGE_SIZE,
-                               "Unused:         %zu%%\n"
-                               "Metadata:       %zu%%\n"
-                               "Average:        %llu\n"
-                               "Sectors per Q:  %zu\n"
-                               "Quantiles:      [",
-                               unused * 100 / (size_t) ca->sb.nbuckets,
-                               btree * 100 / (size_t) ca->sb.nbuckets, sum,
-                               n * ca->sb.bucket_size / (nq + 1));
-
-                for (i = 0; i < nq && ret < (ssize_t) PAGE_SIZE; i++)
-                        ret += snprintf(buf + ret, PAGE_SIZE - ret,
-                                        i < nq - 1 ? "%u " : "%u]\n", q[i]);
-
-                buf[PAGE_SIZE - 1] = '\0';
+                ret = scnprintf(buf, PAGE_SIZE,
+                                "Unused:                %zu%%\n"
+                                "Metadata:      %zu%%\n"
+                                "Average:       %llu\n"
+                                "Sectors per Q: %zu\n"
+                                "Quantiles:     [",
+                                unused * 100 / (size_t) ca->sb.nbuckets,
+                                btree * 100 / (size_t) ca->sb.nbuckets, sum,
+                                n * ca->sb.bucket_size / (ARRAY_SIZE(q) + 1));
+
+                for (i = 0; i < ARRAY_SIZE(q); i++)
+                        ret += scnprintf(buf + ret, PAGE_SIZE - ret,
+                                         "%u ", q[i]);
+                ret--;
+
+                ret += scnprintf(buf + ret, PAGE_SIZE - ret, "]\n");
+
                 return ret;
         }