From: NeilBrown Date: Fri, 6 Jan 2006 08:20:24 +0000 (-0800) Subject: [PATCH] md: fix up some rdev rcu locking in raid5/6 X-Git-Tag: v2.6.16-rc1~936^2~38 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9910f16af35419a5382fa7850eecc220103036fa;p=linux-2.6 [PATCH] md: fix up some rdev rcu locking in raid5/6 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 0d016a844e..0222ba1a6d 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -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; diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c index 7a51553d8b..b5b7a8d0b1 100644 --- a/drivers/md/raid6main.c +++ b/drivers/md/raid6main.c @@ -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; diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h index e9c1c0d4f9..28fcd7533a 100644 --- a/include/linux/raid/raid5.h +++ b/include/linux/raid/raid5.h @@ -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 */