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Date: Wed, 05 Feb 2014 01:41:37 +0900 (JST)
From: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andreas Rohner <andreas.rohner@....net>,
linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org
Subject: Re: [PATCH 3/4] nilfs2: add nilfs_sufile_set_suinfo to update
segment usage
On Mon, 3 Feb 2014 13:38:18 -0800, Andrew Morton wrote:
> On Tue, 4 Feb 2014 01:50:43 +0900 Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp> wrote:
>
>> From: Andreas Rohner <andreas.rohner@....net>
>>
>> This patch introduces the nilfs_sufile_set_suinfo function, which
>> expects an array of nilfs_suinfo_update structures and updates the
>> segment usage information accordingly.
>>
>> This is basically a helper function for the newly introduced
>> NILFS_IOCTL_SET_SUINFO ioctl.
>>
>> ..
>>
>> --- a/fs/nilfs2/sufile.c
>> +++ b/fs/nilfs2/sufile.c
>> @@ -870,6 +870,137 @@ ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
>> }
>>
>> /**
>> + * nilfs_sufile_set_suinfo - sets segment usage info
>> + * @sufile: inode of segment usage file
>> + * @buf: array of suinfo_update
>> + * @supsz: byte size of suinfo_update
>> + * @nsup: size of suinfo_update array
>> + *
>> + * Description: Takes an array of nilfs_suinfo_update structs and updates
>> + * segment usage accordingly. Only the fields indicated by the sup_flags
>> + * are updated.
>> + *
>> + * Return Value: On success, 0 is returned. On error, one of the
>> + * following negative error codes is returned.
>> + *
>> + * %-EIO - I/O error.
>> + *
>> + * %-ENOMEM - Insufficient amount of memory available.
>> + *
>> + * %-EINVAL - Invalid values in input (segment number, flags or nblocks)
>> + */
>> +ssize_t nilfs_sufile_set_suinfo(struct inode *sufile, void *buf,
>> + unsigned supsz, size_t nsup)
>> +{
>> + struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
>> + struct buffer_head *header_bh, *bh;
>> + struct nilfs_suinfo_update *sup, *supend = buf + supsz * nsup;
>> + struct nilfs_segment_usage *su;
>> + void *kaddr;
>> + unsigned long blkoff, prev_blkoff;
>> + int cleansi, cleansu, dirtysi, dirtysu;
>> + long ncleaned = 0, ndirtied = 0;
>> + int ret = 0;
>> +
>> + if (unlikely(nsup == 0))
>> + return ret;
>> +
>> + for (sup = buf; sup < supend; sup = (void *)sup + supsz) {
>> + if (sup->sup_segnum >= nilfs->ns_nsegments
>> + || (sup->sup_flags &
>> + (~0UL << __NR_NILFS_SUINFO_UPDATE_FIELDS))
>> + || (nilfs_suinfo_update_nblocks(sup) &&
>> + sup->sup_sui.sui_nblocks >
>> + nilfs->ns_blocks_per_segment))
>> + return -EINVAL;
>> + }
>> +
>> + down_write(&NILFS_MDT(sufile)->mi_sem);
>> +
>> + ret = nilfs_sufile_get_header_block(sufile, &header_bh);
>> + if (ret < 0)
>> + goto out_sem;
>> +
>> + sup = buf;
>> + blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
>> + ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
>> + if (ret < 0)
>> + goto out_header;
>> +
>> + for (;;) {
>> + kaddr = kmap_atomic(bh->b_page);
>
> Can this buffer_head really be in highmem?
Yes, data blocks of metadata files can be allocated in highmem. This
buffer head is one of them.
>> + su = nilfs_sufile_block_get_segment_usage(
>> + sufile, sup->sup_segnum, bh, kaddr);
>
> Returns an address wthin the kmapped page. I really hope
> nilfs_sufile_block_get_segment_usage() cannot return an address outside
> that page - it appears to do quite a lot of unchecked arithmetic which
> is dependent on stuff which was read from the disk. What it that was
> interfered with or otherwise corrupted?
That's right. Several range checks looks to be needed, for instance,
for segment usage size, checkpoint size, dat entry size, and inode
size. I will try to add these missing checks.
>> + if (nilfs_suinfo_update_lastmod(sup))
>> + su->su_lastmod = cpu_to_le64(sup->sup_sui.sui_lastmod);
>> +
>> + if (nilfs_suinfo_update_nblocks(sup))
>> + su->su_nblocks = cpu_to_le32(sup->sup_sui.sui_nblocks);
>> +
>> + if (nilfs_suinfo_update_flags(sup)) {
>> + /*
>> + * Active flag is a virtual flag projected by running
>> + * nilfs kernel code - drop it not to write it to
>> + * disk.
>> + */
>> + sup->sup_sui.sui_flags &=
>> + ~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
>> +
>> + cleansi = nilfs_suinfo_clean(&sup->sup_sui);
>> + cleansu = nilfs_segment_usage_clean(su);
>> + dirtysi = nilfs_suinfo_dirty(&sup->sup_sui);
>> + dirtysu = nilfs_segment_usage_dirty(su);
>> +
>> + if (cleansi && !cleansu)
>> + ++ncleaned;
>> + else if (!cleansi && cleansu)
>> + --ncleaned;
>> +
>> + if (dirtysi && !dirtysu)
>> + ++ndirtied;
>> + else if (!dirtysi && dirtysu)
>> + --ndirtied;
>> +
>> + su->su_flags = cpu_to_le32(sup->sup_sui.sui_flags);
>> + }
>> +
>> + kunmap_atomic(kaddr);
>
> flush_dcache_page()? Can the page be mapped by userspace?
This page is never mapped to userspace, so flush_dcache_page() looks
unnecessary here.
>> + sup = (void *)sup + supsz;
>> + if (sup >= supend)
>> + break;
>> +
>> + prev_blkoff = blkoff;
>> + blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
>> + if (blkoff == prev_blkoff)
>> + continue;
>> +
>> + /* get different block */
>> + mark_buffer_dirty(bh);
>> + brelse(bh);
>
> put_bh() will suffice - we know bh != NULL.
Agreed. I will fix it later.
>> + ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
>> + if (unlikely(ret < 0))
>> + goto out_mark;
>> + }
>> + mark_buffer_dirty(bh);
>> + brelse(bh);
>
> ditto
Thank you for your review and comments.
Regards,
Ryusuke Konishi
>> + out_mark:
>> + if (ncleaned || ndirtied) {
>> + nilfs_sufile_mod_counter(header_bh, (u64)ncleaned,
>> + (u64)ndirtied);
>> + NILFS_SUI(sufile)->ncleansegs += ncleaned;
>> + }
>> + nilfs_mdt_mark_dirty(sufile);
>> + out_header:
>> + brelse(header_bh);
>> + out_sem:
>> + up_write(&NILFS_MDT(sufile)->mi_sem);
>> + return ret;
>> +}
>> +
>> +/**
>
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