| Message ID | ac8f92701003180539h7228040bm82a0c69d678ec93b@mail.gmail.com |
|---|---|
| State | New, archived |
| Headers | show |
> ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL); > @@ -3811,6 +3813,12 @@ repeat: > list_del(&pa->u.pa_tmp_list); > call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); > } > + if (! list_empty(&list)) { > + if (occurs++ < 2) > + goto best_efforts; > + else > + BUG(); > + } > if (ac) > kmem_cache_free(ext4_ac_cachep, ac); > } Hmm, I'm not sure that BUG() is appropriate here. If there is an I/O error reading the block bitmap, #1, retrying isn't going to help, and #2, bringing down the entire system just because of an I/O error in reading the block bitmap doesn't seem right. Right now, if there is a problem, we just end up leaving the preallocated list on the inode. Does that cause problems later on down the line which you have observed? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
>> ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL); >> @@ -3811,6 +3813,12 @@ repeat: >> list_del(&pa->u.pa_tmp_list); >> call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); >> } >> + if (! list_empty(&list)) { >> + if (occurs++ < 2) >> + goto best_efforts; >> + else >> + BUG(); >> + } >> if (ac) >> kmem_cache_free(ext4_ac_cachep, ac); >> } > > Hmm, I'm not sure that BUG() is appropriate here. If there is an > I/O error reading the block bitmap, #1, retrying isn't going to help, > and #2, bringing down the entire system just because of an I/O error > in reading the block bitmap doesn't seem right. But disk hardware error is not rare, > Right now, if there is a problem, we just end up leaving the > preallocated list on the inode. Does that cause problems later on > down the line which you have observed? > > - Ted and is there still chance to call the call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); function again later on? (I am not sure yet the chance does exist.) If no chance, how about the kmem_cache subsystem then? After reboot, the file system is still reliable, or just with a few lost blocks? Thus it is necessary, at least for me, to make sure whether the chance exists. - zj -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2010-03-19, at 08:17, jing zhang wrote: >>> ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL); >>> @@ -3811,6 +3813,12 @@ repeat: >>> list_del(&pa->u.pa_tmp_list); >>> call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); >>> } >>> + if (! list_empty(&list)) { >>> + if (occurs++ < 2) >>> + goto best_efforts; >>> + else >>> + BUG(); >>> + } >>> if (ac) >>> kmem_cache_free(ext4_ac_cachep, ac); >>> } >> >> Hmm, I'm not sure that BUG() is appropriate here. If there is an >> I/O error reading the block bitmap, #1, retrying isn't going to help, >> and #2, bringing down the entire system just because of an I/O error >> in reading the block bitmap doesn't seem right. > > But disk hardware error is not rare, Exactly, which is the reason why it should not cause the system to hang. The filesystem should handle such errors gracefully if this is possible, return an error to the application, and/or marking the filesystem in error so that it will be checked on next boot, or similar. >> Right now, if there is a problem, we just end up leaving the >> preallocated list on the inode. Does that cause problems later on >> down the line which you have observed? >> >> - Ted > > and is there still chance to call the > call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); > function again later on? (I am not sure yet the chance does exist.) > > If no chance, how about the kmem_cache subsystem then? > After reboot, the file system is still reliable, or just with a few > lost blocks? > > Thus it is necessary, at least for me, to make sure whether the > chance exists. > - zj > -- > To unsubscribe from this list: send the line "unsubscribe linux- > ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- linux-2.6.32/fs/ext4/mballoc.c 2009-12-03 11:51:22.000000000 +0800 +++ zj/mballoc.c 2010-03-18 20:41:32.000000000 +0800 @@ -3717,6 +3717,7 @@ void ext4_discard_preallocations(struct struct list_head list; struct ext4_buddy e4b; int err; + int occurs = 0; if (!S_ISREG(inode->i_mode)) { /*BUG_ON(!list_empty(&ei->i_prealloc_list));*/ @@ -3781,6 +3782,7 @@ repeat: } spin_unlock(&ei->i_prealloc_lock); +best_efforts: list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) { BUG_ON(pa->pa_type != MB_INODE_PA); ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL); @@ -3811,6 +3813,12 @@ repeat: list_del(&pa->u.pa_tmp_list); call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); } + if (! list_empty(&list)) { + if (occurs++ < 2) + goto best_efforts; + else + BUG(); + } if (ac) kmem_cache_free(ext4_ac_cachep, ac); }