[PATCH] md: fix up some rdev rcu locking in raid5/6
NeilBrown [Fri, 6 Jan 2006 08:20:24 +0000 (00:20 -0800)]
There is this "FIXME" comment with a typo in it!!  that been annoying me for
days, so I just had to remove it.

conf->disks[i].rdev should only be accessed if
  - we know we hold a reference or
  - the mddev->reconfig_sem is down or
  - we have a rcu_readlock

handle_stripe was referencing rdev in three places without any of these.  For
the first two, get an rcu_readlock.  For the last, the same access
(md_sync_acct call) is made a little later after the rdev has been claimed
under and rcu_readlock, if R5_Syncio is set.  So just use that access...
However R5_Syncio isn't really needed as the 'syncing' variable contains the
same information.  So use that instead.

Issues, comment, and fix are identical in raid5 and raid6.

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

drivers/md/raid5.c
drivers/md/raid6main.c
include/linux/raid/raid5.h

index 0d016a8..0222ba1 100644 (file)
@@ -961,11 +961,11 @@ static void handle_stripe(struct stripe_head *sh)
        syncing = test_bit(STRIPE_SYNCING, &sh->state);
        /* Now to look around and see what can be done */
 
+       rcu_read_lock();
        for (i=disks; i--; ) {
                mdk_rdev_t *rdev;
                dev = &sh->dev[i];
                clear_bit(R5_Insync, &dev->flags);
-               clear_bit(R5_Syncio, &dev->flags);
 
                PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
                        i, dev->flags, dev->toread, dev->towrite, dev->written);
@@ -1004,7 +1004,7 @@ static void handle_stripe(struct stripe_head *sh)
                                non_overwrite++;
                }
                if (dev->written) written++;
-               rdev = conf->disks[i].rdev; /* FIXME, should I be looking rdev */
+               rdev = rcu_dereference(conf->disks[i].rdev);
                if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
@@ -1017,6 +1017,7 @@ static void handle_stripe(struct stripe_head *sh)
                } else
                        set_bit(R5_Insync, &dev->flags);
        }
+       rcu_read_unlock();
        PRINTK("locked=%d uptodate=%d to_read=%d"
                " to_write=%d failed=%d failed_num=%d\n",
                locked, uptodate, to_read, to_write, failed, failed_num);
@@ -1028,10 +1029,13 @@ static void handle_stripe(struct stripe_head *sh)
                        int bitmap_end = 0;
 
                        if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
-                               mdk_rdev_t *rdev = conf->disks[i].rdev;
+                               mdk_rdev_t *rdev;
+                               rcu_read_lock();
+                               rdev = rcu_dereference(conf->disks[i].rdev);
                                if (rdev && test_bit(In_sync, &rdev->flags))
                                        /* multiple read failures in one stripe */
                                        md_error(conf->mddev, rdev);
+                               rcu_read_unlock();
                        }
 
                        spin_lock_irq(&conf->device_lock);
@@ -1180,9 +1184,6 @@ static void handle_stripe(struct stripe_head *sh)
                                        locked++;
                                        PRINTK("Reading block %d (sync=%d)\n", 
                                                i, syncing);
-                                       if (syncing)
-                                               md_sync_acct(conf->disks[i].rdev->bdev,
-                                                            STRIPE_SECTORS);
                                }
                        }
                }
@@ -1326,7 +1327,6 @@ static void handle_stripe(struct stripe_head *sh)
                        clear_bit(STRIPE_DEGRADED, &sh->state);
                        locked++;
                        set_bit(STRIPE_INSYNC, &sh->state);
-                       set_bit(R5_Syncio, &dev->flags);
                }
        }
        if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
@@ -1392,7 +1392,7 @@ static void handle_stripe(struct stripe_head *sh)
                rcu_read_unlock();
  
                if (rdev) {
-                       if (test_bit(R5_Syncio, &sh->dev[i].flags))
+                       if (syncing)
                                md_sync_acct(rdev->bdev, STRIPE_SECTORS);
 
                        bi->bi_bdev = rdev->bdev;
index 7a51553..b5b7a8d 100644 (file)
@@ -1060,11 +1060,11 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
        syncing = test_bit(STRIPE_SYNCING, &sh->state);
        /* Now to look around and see what can be done */
 
+       rcu_read_lock();
        for (i=disks; i--; ) {
                mdk_rdev_t *rdev;
                dev = &sh->dev[i];
                clear_bit(R5_Insync, &dev->flags);
-               clear_bit(R5_Syncio, &dev->flags);
 
                PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
                        i, dev->flags, dev->toread, dev->towrite, dev->written);
@@ -1103,7 +1103,7 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                                non_overwrite++;
                }
                if (dev->written) written++;
-               rdev = conf->disks[i].rdev; /* FIXME, should I be looking rdev */
+               rdev = rcu_dereference(conf->disks[i].rdev);
                if (!rdev || !test_bit(In_sync, &rdev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
@@ -1117,6 +1117,7 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                } else
                        set_bit(R5_Insync, &dev->flags);
        }
+       rcu_read_unlock();
        PRINTK("locked=%d uptodate=%d to_read=%d"
               " to_write=%d failed=%d failed_num=%d,%d\n",
               locked, uptodate, to_read, to_write, failed,
@@ -1129,10 +1130,13 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                        int bitmap_end = 0;
 
                        if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
-                               mdk_rdev_t *rdev = conf->disks[i].rdev;
+                               mdk_rdev_t *rdev;
+                               rcu_read_lock();
+                               rdev = rcu_dereference(conf->disks[i].rdev);
                                if (rdev && test_bit(In_sync, &rdev->flags))
                                        /* multiple read failures in one stripe */
                                        md_error(conf->mddev, rdev);
+                               rcu_read_unlock();
                        }
 
                        spin_lock_irq(&conf->device_lock);
@@ -1307,9 +1311,6 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                                        locked++;
                                        PRINTK("Reading block %d (sync=%d)\n",
                                                i, syncing);
-                                       if (syncing)
-                                               md_sync_acct(conf->disks[i].rdev->bdev,
-                                                            STRIPE_SECTORS);
                                }
                        }
                }
@@ -1463,14 +1464,12 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                                locked++;
                                set_bit(R5_LOCKED, &dev->flags);
                                set_bit(R5_Wantwrite, &dev->flags);
-                               set_bit(R5_Syncio, &dev->flags);
                        }
                        if (failed >= 1) {
                                dev = &sh->dev[failed_num[0]];
                                locked++;
                                set_bit(R5_LOCKED, &dev->flags);
                                set_bit(R5_Wantwrite, &dev->flags);
-                               set_bit(R5_Syncio, &dev->flags);
                        }
 
                        if (update_p) {
@@ -1478,14 +1477,12 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                                locked ++;
                                set_bit(R5_LOCKED, &dev->flags);
                                set_bit(R5_Wantwrite, &dev->flags);
-                               set_bit(R5_Syncio, &dev->flags);
                        }
                        if (update_q) {
                                dev = &sh->dev[qd_idx];
                                locked++;
                                set_bit(R5_LOCKED, &dev->flags);
                                set_bit(R5_Wantwrite, &dev->flags);
-                               set_bit(R5_Syncio, &dev->flags);
                        }
                        clear_bit(STRIPE_DEGRADED, &sh->state);
 
@@ -1557,7 +1554,7 @@ static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
                rcu_read_unlock();
 
                if (rdev) {
-                       if (test_bit(R5_Syncio, &sh->dev[i].flags))
+                       if (syncing)
                                md_sync_acct(rdev->bdev, STRIPE_SECTORS);
 
                        bi->bi_bdev = rdev->bdev;
index e9c1c0d..28fcd75 100644 (file)
@@ -152,7 +152,6 @@ struct stripe_head {
 #define        R5_Insync       3       /* rdev && rdev->in_sync at start */
 #define        R5_Wantread     4       /* want to schedule a read */
 #define        R5_Wantwrite    5
-#define        R5_Syncio       6       /* this io need to be accounted as resync io */
 #define        R5_Overlap      7       /* There is a pending overlapping request on this block */
 #define        R5_ReadError    8       /* seen a read error here recently */
 #define        R5_ReWrite      9       /* have tried to over-write the readerror */