sysctl: add proc_do_large_bitmap

The new function can be used to read/write large bitmaps via /proc. A
comma separated range format is used for compact output and input
(e.g. 1,3-4,10-10).

Writing into the file will first reset the bitmap then update it
based on the given input.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f66014c..7bb5cb6 100644 (file)
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -980,6 +980,8 @@ extern int proc_doulongvec_minmax(struct ctl_table *, int,
                                  void __user *, size_t *, loff_t *);
 extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
                                      void __user *, size_t *, loff_t *);
+extern int proc_do_large_bitmap(struct ctl_table *, int,
+                               void __user *, size_t *, loff_t *);
 
 /*
  * Register a set of sysctl names by calling register_sysctl_table

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4a97620..bcfb79e 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2049,6 +2049,16 @@ static size_t proc_skip_spaces(char **buf)
        return ret;
 }
 
+static void proc_skip_char(char **buf, size_t *size, const char v)
+{
+       while (*size) {
+               if (**buf != v)
+                       break;
+               (*size)--;
+               (*buf)++;
+       }
+}
+
 #define TMPBUFLEN 22
 /**
  * proc_get_long - reads an ASCII formated integer from a user buffer
@@ -2675,6 +2685,157 @@ static int proc_do_cad_pid(struct ctl_table *table, int write,
        return 0;
 }
 
+/**
+ * proc_do_large_bitmap - read/write from/to a large bitmap
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * The bitmap is stored at table->data and the bitmap length (in bits)
+ * in table->maxlen.
+ *
+ * We use a range comma separated format (e.g. 1,3-4,10-10) so that
+ * large bitmaps may be represented in a compact manner. Writing into
+ * the file will clear the bitmap then update it with the given input.
+ *
+ * Returns 0 on success.
+ */
+int proc_do_large_bitmap(struct ctl_table *table, int write,
+                        void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+       int err = 0;
+       bool first = 1;
+       size_t left = *lenp;
+       unsigned long bitmap_len = table->maxlen;
+       unsigned long *bitmap = (unsigned long *) table->data;
+       unsigned long *tmp_bitmap = NULL;
+       char tr_a[] = { '-', ',', '\n' }, tr_b[] = { ',', '\n', 0 }, c;
+
+       if (!bitmap_len || !left || (*ppos && !write)) {
+               *lenp = 0;
+               return 0;
+       }
+
+       if (write) {
+               unsigned long page = 0;
+               char *kbuf;
+
+               if (left > PAGE_SIZE - 1)
+                       left = PAGE_SIZE - 1;
+
+               page = __get_free_page(GFP_TEMPORARY);
+               kbuf = (char *) page;
+               if (!kbuf)
+                       return -ENOMEM;
+               if (copy_from_user(kbuf, buffer, left)) {
+                       free_page(page);
+                       return -EFAULT;
+                }
+               kbuf[left] = 0;
+
+               tmp_bitmap = kzalloc(BITS_TO_LONGS(bitmap_len) * sizeof(unsigned long),
+                                    GFP_KERNEL);
+               if (!tmp_bitmap) {
+                       free_page(page);
+                       return -ENOMEM;
+               }
+               proc_skip_char(&kbuf, &left, '\n');
+               while (!err && left) {
+                       unsigned long val_a, val_b;
+                       bool neg;
+
+                       err = proc_get_long(&kbuf, &left, &val_a, &neg, tr_a,
+                                            sizeof(tr_a), &c);
+                       if (err)
+                               break;
+                       if (val_a >= bitmap_len || neg) {
+                               err = -EINVAL;
+                               break;
+                       }
+
+                       val_b = val_a;
+                       if (left) {
+                               kbuf++;
+                               left--;
+                       }
+
+                       if (c == '-') {
+                               err = proc_get_long(&kbuf, &left, &val_b,
+                                                    &neg, tr_b, sizeof(tr_b),
+                                                    &c);
+                               if (err)
+                                       break;
+                               if (val_b >= bitmap_len || neg ||
+                                   val_a > val_b) {
+                                       err = -EINVAL;
+                                       break;
+                               }
+                               if (left) {
+                                       kbuf++;
+                                       left--;
+                               }
+                       }
+
+                       while (val_a <= val_b)
+                               set_bit(val_a++, tmp_bitmap);
+
+                       first = 0;
+                       proc_skip_char(&kbuf, &left, '\n');
+               }
+               free_page(page);
+       } else {
+               unsigned long bit_a, bit_b = 0;
+
+               while (left) {
+                       bit_a = find_next_bit(bitmap, bitmap_len, bit_b);
+                       if (bit_a >= bitmap_len)
+                               break;
+                       bit_b = find_next_zero_bit(bitmap, bitmap_len,
+                                                  bit_a + 1) - 1;
+
+                       if (!first) {
+                               err = proc_put_char(&buffer, &left, ',');
+                               if (err)
+                                       break;
+                       }
+                       err = proc_put_long(&buffer, &left, bit_a, false);
+                       if (err)
+                               break;
+                       if (bit_a != bit_b) {
+                               err = proc_put_char(&buffer, &left, '-');
+                               if (err)
+                                       break;
+                               err = proc_put_long(&buffer, &left, bit_b, false);
+                               if (err)
+                                       break;
+                       }
+
+                       first = 0; bit_b++;
+               }
+               if (!err)
+                       err = proc_put_char(&buffer, &left, '\n');
+       }
+
+       if (!err) {
+               if (write) {
+                       if (*ppos)
+                               bitmap_or(bitmap, bitmap, tmp_bitmap, bitmap_len);
+                       else
+                               memcpy(bitmap, tmp_bitmap,
+                                       BITS_TO_LONGS(bitmap_len) * sizeof(unsigned long));
+               }
+               kfree(tmp_bitmap);
+               *lenp -= left;
+               *ppos += *lenp;
+               return 0;
+       } else {
+               kfree(tmp_bitmap);
+               return err;
+       }
+}
+
 #else /* CONFIG_PROC_FS */
 
 int proc_dostring(struct ctl_table *table, int write,