From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tristan Ye Date: Tue, 08 Mar 2011 14:53:53 +0800 Subject: [Ocfs2-devel] [PATCH 1/3] ocfs2: Add ocfs2_trim_fs for SSD trim support. In-Reply-To: <4D75CFCB.6000501@tao.ma> References: <4D74AD52.4030502@tao.ma> <1299492356-7329-1-git-send-email-tm@tao.ma> <4D75B6DF.3030508@oracle.com> <4D75C468.8050707@tao.ma> <4D75CB69.5080908@oracle.com> <4D75CFCB.6000501@tao.ma> Message-ID: <4D75D281.5000003@oracle.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Tao Ma wrote: > On 03/08/2011 02:23 PM, Tristan Ye wrote: >> Tao Ma wrote: >>> On 03/08/2011 12:55 PM, Tristan Ye wrote: >>>> Hi Tao, >>>> >>>> Most of codes looks pretty neat to me, few comments inlined below: >>> Thanks for the review. >>>> Tao Ma wrote: >>>>> From: Tao Ma >>>>> >>>>> Add ocfs2_trim_fs to support trimming freed clusters in the >>>>> volume. A range will be given and all the freed clusters greater >>>>> than minlen will be discarded to the block layer. >>>>> >>>>> Signed-off-by: Tao Ma >>>>> --- >>>>> fs/ocfs2/alloc.c | 154 >>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>>> fs/ocfs2/alloc.h | 1 + >>>>> 2 files changed, 155 insertions(+), 0 deletions(-) >>>>> >>>>> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c >>>>> index b27a0d8..6e1b3b5 100644 >>>>> --- a/fs/ocfs2/alloc.c >>>>> +++ b/fs/ocfs2/alloc.c >>>>> @@ -29,6 +29,7 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> >>>>> #include >>>>> >>>>> @@ -7184,3 +7185,156 @@ out_commit: >>>>> out: >>>>> return ret; >>>>> } >>>>> + >>>>> +static int ocfs2_trim_extent(struct super_block *sb, >>>>> + struct ocfs2_group_desc *gd, >>>>> + int start, int count) >>>>> +{ >>>>> + u64 discard; >>>>> + >>>>> + count = ocfs2_clusters_to_blocks(sb, count); >>>>> + discard = le64_to_cpu(gd->bg_blkno) + >>>>> + ocfs2_clusters_to_blocks(sb, start); >>>>> + >>>>> + return sb_issue_discard(sb, discard, count, GFP_NOFS, 0); >>>>> +} >>>>> + >>>>> +static int ocfs2_trim_group(struct super_block *sb, >>>>> + struct ocfs2_group_desc *gd, >>>>> + int start, int max, int minbits) >>>>> +{ >>>>> + int ret = 0, count = 0, next; >>>>> + void *bitmap = gd->bg_bitmap; >>>>> + >>>>> + while (start < max) { >>>>> + start = ocfs2_find_next_zero_bit(bitmap, max, start); >>>>> + if (start >= max) >>>>> + break; >>>> /* What if the 'start' stands within a hole */ >>>> >>>> if (ocfs2_test_bit(...)) { >>>> start = ocfs2_find_next_zero_bit(...); >>>> if ((start == -1) || (start >= max)) >>>> break; >>>> } >>>> >>>>> + next = ocfs2_find_next_bit(bitmap, max, start); >>>> next = ocfs2_find_next_bit(...); >>>> if (next == -1) >>>> break; >>> next will be set to "-1"? sorry, but where do you get it? >>>> if (next > max) >>>> next = max; >>> again, ocfs2_find_next_bit will return a value larger than 'max'? I am >>> afraid not. Otherwise, it will be nonsense to pass a 'max' to it. >> >> Say we're handling the last group, and the 'start + len' was within a >> hole, then the 'max' >> is 'first_bit + len', while the next none-zero bit we found may be >> larger than 'max', isn't >> that possible? > ocfs2_find_next_bit(and ext2_find_next_bit) won't parse, check and > return 'bit' after 'max'. otherwise there should be a problem of memory > overflow(you read and check some memory which isn't owned and handled by > you). So the same goes here. If it can return a value larger than 'max', > every caller will have to check the overflow. That would be too painful. Oh, you may misunderstood my words, the 'max' you passed to ocfs2_find_next_bit() may not be the ending-edge of the cluster group(bitmap), it may be the end of what user specified for TRIMing, therefore the 'next'(ending-edge for a wanted hole) bit you found from ocfs2_find_next_bit() might be larger than 'max', is that possible? >>>>> +int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range) >>>>> +{ >>>>> + struct ocfs2_super *osb = OCFS2_SB(sb); >>>>> + u64 start, len, minlen, trimmed, first_group, last_group, group; >>>> why not using u32 start, len, minlen, trimmed; >>> we may use 64 bit clusters later I guess. And what's more, they will be >>> set by the user later. and it may overflow. Say the user pass a u64 >>> range->len, it will overflow with range->len >> osb->s_clustersize_bits. >> I just found we were using u32 for counting clusters all around ocfs2 >> codes, e.g truncate/punching_hole >> codes, also passing an u64 byte_offset from userspace, so my original >> intention is to keep an unification;-) >> >> Overflow can theoretically happen anyway, however, it's not very likely >> to pass a 16TB+ byte_offset from userspace. > I am afraid it is very likely. So say you want to trim all the clusters > within the volume, how could you set 'range->len'? Will you first fdisk > to get the volume size and then set it accordingly? > Most guys will set it to ULLONG_MAX and let the file system handles it. > This is not my personal view, please check this article: > http://lwn.net/Articles/417809/ > Jonathan also suggests to set len to ULLONG_MAX so that you can trim the > whole volume. Nice self-defense;-), how about the overflow risk in truncate/punching-hole codes, where u32 were being used for cluster counting. > > Regards, > Tao