* [PATCH md ] Fix BUG in raid5 resync code. [not found] <20040604165208.8646.patches@notabene> @ 2004-06-04 6:55 ` NeilBrown 2004-06-04 7:10 ` David Greaves 0 siblings, 1 reply; 6+ messages in thread From: NeilBrown @ 2004-06-04 6:55 UTC (permalink / raw) To: Marcelo Tosatti; +Cc: linux-raid Hi Marcelo, This patch fixes a long standing bug in raid5, that is fairly hard to hit. As the comment below says, the if() condition on the for loop is there to optimised out the loop if it is known that it isn't needed, so making the test broader (as this patch does) cannot possibly hurt in correctness. Please include this in an upcoming release. Thanks, NeilBrown (patch against 2.4.27-pre5) ### Comments for Changeset This condition on this loop is primarily to avoid the loop if it doesn't appear to be needed. However it optimises a little too much and there is a case where it skips the loop when it is really needed. This patch fixes it. Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au> ### Diffstat output ./drivers/md/raid5.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-) diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c --- ./drivers/md/raid5.c~current~ 2004-06-04 16:50:34.000000000 +1000 +++ ./drivers/md/raid5.c 2004-06-04 16:51:06.000000000 +1000 @@ -950,7 +950,7 @@ static void handle_stripe(struct stripe_ /* Now we might consider reading some blocks, either to check/generate * parity, or to satisfy requests */ - if (to_read || (syncing && (uptodate+failed < disks))) { + if (to_read || (syncing && (uptodate < disks))) { for (i=disks; i--;) { bh = sh->bh_cache[i]; if (!buffer_locked(bh) && !buffer_uptodate(bh) && ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH md ] Fix BUG in raid5 resync code. 2004-06-04 6:55 ` [PATCH md ] Fix BUG in raid5 resync code NeilBrown @ 2004-06-04 7:10 ` David Greaves 2004-06-04 12:04 ` Neil Brown 0 siblings, 1 reply; 6+ messages in thread From: David Greaves @ 2004-06-04 7:10 UTC (permalink / raw) To: NeilBrown; +Cc: linux-raid Hi Neil Given I'm about to resync about 400Gb of data I'd like to check this before blindly storming ahead... :) Would the following be the correct patch against 2.6.6? --- drivers/md/raid5.c~ 2004-05-30 18:38:49.000000000 +0100 +++ drivers/md/raid5.c 2004-06-04 09:06:12.000000000 +0100 @@ -1037,7 +1037,7 @@ * parity, or to satisfy requests * or to load a block that is being partially written. */ - if (to_read || non_overwrite || (syncing && (uptodate+failed < disks))) { + if (to_read || non_overwrite || (syncing && (uptodate < disks))) { for (i=disks; i--;) { dev = &sh->dev[i]; if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) && c Thanks David NeilBrown wrote: >Hi Marcelo, > This patch fixes a long standing bug in raid5, that is fairly hard to hit. > > As the comment below says, the if() condition on the for loop is there to >optimised out the loop if it is known that it isn't needed, so making the test >broader (as this patch does) cannot possibly hurt in correctness. >Please include this in an upcoming release. >Thanks, >NeilBrown > >(patch against 2.4.27-pre5) > >### Comments for Changeset > > >This condition on this loop is primarily to avoid the loop >if it doesn't appear to be needed. However it optimises >a little too much and there is a case where it skips the >loop when it is really needed. This patch fixes it. > > >Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au> > >### Diffstat output > ./drivers/md/raid5.c | 2 +- > 1 files changed, 1 insertion(+), 1 deletion(-) > >diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c >--- ./drivers/md/raid5.c~current~ 2004-06-04 16:50:34.000000000 +1000 >+++ ./drivers/md/raid5.c 2004-06-04 16:51:06.000000000 +1000 >@@ -950,7 +950,7 @@ static void handle_stripe(struct stripe_ > /* Now we might consider reading some blocks, either to check/generate > * parity, or to satisfy requests > */ >- if (to_read || (syncing && (uptodate+failed < disks))) { >+ if (to_read || (syncing && (uptodate < disks))) { > for (i=disks; i--;) { > bh = sh->bh_cache[i]; > if (!buffer_locked(bh) && !buffer_uptodate(bh) && >- >To unsubscribe from this list: send the line "unsubscribe linux-raid" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html > > > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH md ] Fix BUG in raid5 resync code. 2004-06-04 7:10 ` David Greaves @ 2004-06-04 12:04 ` Neil Brown 0 siblings, 0 replies; 6+ messages in thread From: Neil Brown @ 2004-06-04 12:04 UTC (permalink / raw) To: David Greaves; +Cc: linux-raid On Friday June 4, david@dgreaves.com wrote: > Hi Neil > > Given I'm about to resync about 400Gb of data I'd like to check this > before blindly storming ahead... :) > > Would the following be the correct patch against 2.6.6? Yes. Remove the "+failed". NeilBrown > > --- drivers/md/raid5.c~ 2004-05-30 18:38:49.000000000 +0100 > +++ drivers/md/raid5.c 2004-06-04 09:06:12.000000000 +0100 > @@ -1037,7 +1037,7 @@ > * parity, or to satisfy requests > * or to load a block that is being partially written. > */ > - if (to_read || non_overwrite || (syncing && (uptodate+failed < > disks))) { > + if (to_read || non_overwrite || (syncing && (uptodate < disks))) { > for (i=disks; i--;) { > dev = &sh->dev[i]; > if (!test_bit(R5_LOCKED, &dev->flags) && > !test_bit(R5_UPTODATE, &dev->flags) && > c > ^ permalink raw reply [flat|nested] 6+ messages in thread
[parent not found: <20040604163651.7946.patches@notabene>]
* [PATCH md ] Fix BUG in raid5 resync code. [not found] <20040604163651.7946.patches@notabene> @ 2004-06-04 6:38 ` NeilBrown 2004-06-07 9:33 ` Nick Maynard 0 siblings, 1 reply; 6+ messages in thread From: NeilBrown @ 2004-06-04 6:38 UTC (permalink / raw) To: Andrew Morton; +Cc: linux-raid Today I lucked upon a bug in raid5 that appears to have been there since 2.4.0 and earlier. I guess it doesn't trigger very often. 2.4 will need a similar fix. ### Comments for Changeset This condtion on this loop is primarily to avoid the loop if it doesn't appear to be needed. However it optimises a little too much and there is a case where it skips the loop when it is really needed. This patch fixes it. Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au> ### Diffstat output ./drivers/md/raid5.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-) diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c --- ./drivers/md/raid5.c~current~ 2004-06-04 16:36:19.000000000 +1000 +++ ./drivers/md/raid5.c 2004-06-04 16:36:28.000000000 +1000 @@ -1037,7 +1037,7 @@ static void handle_stripe(struct stripe_ * parity, or to satisfy requests * or to load a block that is being partially written. */ - if (to_read || non_overwrite || (syncing && (uptodate+failed < disks))) { + if (to_read || non_overwrite || (syncing && (uptodate < disks))) { for (i=disks; i--;) { dev = &sh->dev[i]; if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) && ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH md ] Fix BUG in raid5 resync code. 2004-06-04 6:38 ` NeilBrown @ 2004-06-07 9:33 ` Nick Maynard 2004-06-07 23:01 ` Neil Brown 0 siblings, 1 reply; 6+ messages in thread From: Nick Maynard @ 2004-06-07 9:33 UTC (permalink / raw) To: NeilBrown; +Cc: Andrew Morton, linux-raid Hi Neil, > Today I lucked upon a bug in raid5 that appears to have been there > since 2.4.0 and earlier. I guess it doesn't trigger very often. > > 2.4 will need a similar fix. <snip> Do you have any idea when we can expect this fix ported to 2.4? Also, when the 2.6 kernel series will include it? Thanks, -- Nick Maynard nick.maynard@alumni.doc.ic.ac.uk ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH md ] Fix BUG in raid5 resync code. 2004-06-07 9:33 ` Nick Maynard @ 2004-06-07 23:01 ` Neil Brown 0 siblings, 0 replies; 6+ messages in thread From: Neil Brown @ 2004-06-07 23:01 UTC (permalink / raw) To: Nick Maynard; +Cc: Andrew Morton, linux-raid On Monday June 7, nick.maynard@alumni.doc.ic.ac.uk wrote: > Hi Neil, > > > Today I lucked upon a bug in raid5 that appears to have been there > > since 2.4.0 and earlier. I guess it doesn't trigger very often. > > > > 2.4 will need a similar fix. > <snip> > > Do you have any idea when we can expect this fix ported to 2.4? It is in the linux-2.4 bk repository: http://linux.bkbits.com:8080/linux-2.4/cset@40c31f28n8OMv8RVMIjLPDkq3APFWA?nav=index.html|ChangeSet@-2d so it will be in the next (pre)release. > Also, when the 2.6 kernel series will include it? It is in Linux 2.6.7-rc3 http://linux.bkbits.com:8080/linux-2.5/cset@40c209c4CQWb5gFyz-f96tQ8QaBv-A?nav=index.html|ChangeSet@-3d NeilBrown ^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <20040604165208.8646.patches@notabene>
2004-06-04 6:55 ` [PATCH md ] Fix BUG in raid5 resync code NeilBrown
2004-06-04 7:10 ` David Greaves
2004-06-04 12:04 ` Neil Brown
[not found] <20040604163651.7946.patches@notabene>
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2004-06-07 9:33 ` Nick Maynard
2004-06-07 23:01 ` Neil Brown
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