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>

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 4d9cca4..29228b8 100644 (file)
--- 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;
        }