[PATCH] md: Allow the write_mostly flag to be set via sysfs

It appears in /sys/mdX/md/dev-YYY/state
and can be set or cleared by writing 'writemostly' or '-writemostly'
respectively.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/md.txt b/Documentation/md.txt
index f3d418b..0668f9d 100644 (file)
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -309,6 +309,9 @@ Each directory contains:
              faulty   - device has been kicked from active use due to
                          a detected fault
              in_sync  - device is a fully in-sync member of the array
+             writemostly - device will only be subject to read
+                        requests if there are no other options.
+                        This applies only to raid1 arrays.
              spare    - device is working, but not a full member.
                         This includes spares that are in the process
                         of being recoverred to
@@ -316,6 +319,8 @@ Each directory contains:
        This can be written to.
        Writing "faulty"  simulates a failure on the device.
        Writing "remove" removes the device from the array.
+       Writing "writemostly" sets the writemostly flag.
+       Writing "-writemostly" clears the writemostly flag.
 
       errors
        An approximate count of read errors that have been detected on

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 8603c06..331b1bc 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1737,6 +1737,10 @@ state_show(mdk_rdev_t *rdev, char *page)
                len += sprintf(page+len, "%sin_sync",sep);
                sep = ",";
        }
+       if (test_bit(WriteMostly, &rdev->flags)) {
+               len += sprintf(page+len, "%swrite_mostly",sep);
+               sep = ",";
+       }
        if (!test_bit(Faulty, &rdev->flags) &&
            !test_bit(In_sync, &rdev->flags)) {
                len += sprintf(page+len, "%sspare", sep);
@@ -1751,6 +1755,8 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
        /* can write
         *  faulty  - simulates and error
         *  remove  - disconnects the device
+        *  writemostly - sets write_mostly
+        *  -writemostly - clears write_mostly
         */
        int err = -EINVAL;
        if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
@@ -1766,6 +1772,12 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
                        md_new_event(mddev);
                        err = 0;
                }
+       } else if (cmd_match(buf, "writemostly")) {
+               set_bit(WriteMostly, &rdev->flags);
+               err = 0;
+       } else if (cmd_match(buf, "-writemostly")) {
+               clear_bit(WriteMostly, &rdev->flags);
+               err = 0;
        }
        return err ? err : len;
 }