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SubjectRe: [PATCH] f2fs: introduce cur_reserved_blocks in sysfs
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It may block the system in such case, but so does the hard version 
design. In the hard version,
when reserve_blocks is set to the value = user_block_count -
total_valid_block_count, then
the user free space can also drop to zero and has the same problem. IMO,
kernel does not need
to take this responsibility, it's android's responsibility.

On 2017/8/10 19:26, Chao Yu wrote:
> On 2017/8/10 11:58, Yunlong Song wrote:
>> I think the aim of reserved_blocks function is to leave space for f2fs
>> and FTL, so I change it to a
>> soft version so that it can be used to fit to the data image which does
>> not satisfy the hard version,
>> especially for backward compatibility when updated kernel with new
>> default reserved_blocks set
>> (currently it is initially set 0 as default, but can be set any value
>> with my new patch).
>>
>> As for the uid/gid, does current f2fs space management design consider
>> this issue? IMO, I think we
> Upper layer application has considered this issue, as when free space touchs the
> threshold, system will block any operation and give a hint to clean up user's
> data. So w/o uid/gid reserved block, it will be OK. But for your requirement,
> user free space will drop to zero, and before current reserved block number
> touch soft reserved block limitation, user can only do deletion, so in this
> time, if any system/service flow depends on file creation, could result in
> blocking the system.
>
>> can just ensure the reserved space for file system no matter user/system
>> type. Whether the value of
>> reserved_blocks is OK or not, should not be filesystem's issue.
>> Filesystem just provide this interface,
>> and the upper layer, such as android vold should take care of the value
>> of reserved_blocks and make
>> sure its value is appropriate and will not block any activation of
>> system user, if it really happens, android
>> should change the value dynamically, it is fine, since we make
>> reserved_blocks to a soft version.
> We can not make sure in strategy changing flow, there is no file creation
> dependence. Even if we can, if the reserved_blocks is not appropriate, why not
> setting it correctly before?
>
> Thanks,
>
>> On 2017/8/10 11:15, Chao Yu wrote:
>>> On 2017/8/8 21:43, Yunlong Song wrote:
>>>> In this patch, we add a new sysfs interface, we can use it to gradually achieve
>>>> the reserved_blocks finally, even when reserved_blocks is initially set over
>>>> user_block_count - total_valid_block_count. This is very useful, especially when
>>>> we upgrade kernel with new reserved_blocks value, but old disk image unluckily has
>>>> user_block_count - total_valid_block_count smaller than the desired reserved_blocks.
>>>> With this patch, f2fs can try its best to reserve space and get close to the
>>>> reserved_blocks, and the current value of achieved reserved_blocks can be shown
>>>> in real time.
>>> Oh, this looks like a soft limitation in quota system, but original
>>> reserved_blocks implementation likes a hard one, so this patch changes the
>>> semantics of reserved_blocks.
>>>
>>> Actually, I doubt that it would be hard to reserve all left free space in real
>>> user scenario now, since system user's activation may depend on free space of
>>> data partition due to file creation requirement, so w/o supporting feature of
>>> uid/gid reserved block, soft reservation will block any activation of system
>>> user, such as android.
>>>
>>> Thanks,
>>>
>>>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
>>>> ---
>>>> Documentation/ABI/testing/sysfs-fs-f2fs | 6 ++++++
>>>> fs/f2fs/f2fs.h | 9 +++++++--
>>>> fs/f2fs/super.c | 4 +++-
>>>> fs/f2fs/sysfs.c | 15 ++++++++++-----
>>>> 4 files changed, 26 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> index 11b7f4e..bdbb9f3 100644
>>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> @@ -151,3 +151,9 @@ Date: August 2017
>>>> Contact: "Jaegeuk Kim" <jaegeuk@kernel.org>
>>>> Description:
>>>> Controls sleep time of GC urgent mode
>>>> +
>>>> +What: /sys/fs/f2fs/<disk>/cur_reserved_blocks
>>>> +Date: August 2017
>>>> +Contact: "Yunlong Song" <yunlong.song@huawei.com>
>>>> +Description:
>>>> + Shows current reserved blocks in system.
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index cea329f..3b7056f 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -1040,6 +1040,7 @@ struct f2fs_sb_info {
>>>> block_t discard_blks; /* discard command candidats */
>>>> block_t last_valid_block_count; /* for recovery */
>>>> block_t reserved_blocks; /* configurable reserved blocks */
>>>> + block_t cur_reserved_blocks; /* current reserved blocks */
>>>>
>>>> u32 s_next_generation; /* for NFS support */
>>>>
>>>> @@ -1514,7 +1515,7 @@ static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
>>>>
>>>> spin_lock(&sbi->stat_lock);
>>>> sbi->total_valid_block_count += (block_t)(*count);
>>>> - avail_user_block_count = sbi->user_block_count - sbi->reserved_blocks;
>>>> + avail_user_block_count = sbi->user_block_count - sbi->cur_reserved_blocks;
>>>> if (unlikely(sbi->total_valid_block_count > avail_user_block_count)) {
>>>> diff = sbi->total_valid_block_count - avail_user_block_count;
>>>> *count -= diff;
>>>> @@ -1548,6 +1549,8 @@ static inline void dec_valid_block_count(struct f2fs_sb_info *sbi,
>>>> f2fs_bug_on(sbi, sbi->total_valid_block_count < (block_t) count);
>>>> f2fs_bug_on(sbi, inode->i_blocks < sectors);
>>>> sbi->total_valid_block_count -= (block_t)count;
>>>> + sbi->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>> + sbi->cur_reserved_blocks + count);
>>>> spin_unlock(&sbi->stat_lock);
>>>> f2fs_i_blocks_write(inode, count, false, true);
>>>> }
>>>> @@ -1694,7 +1697,7 @@ static inline int inc_valid_node_count(struct f2fs_sb_info *sbi,
>>>> spin_lock(&sbi->stat_lock);
>>>>
>>>> valid_block_count = sbi->total_valid_block_count + 1;
>>>> - if (unlikely(valid_block_count + sbi->reserved_blocks >
>>>> + if (unlikely(valid_block_count + sbi->cur_reserved_blocks >
>>>> sbi->user_block_count)) {
>>>> spin_unlock(&sbi->stat_lock);
>>>> goto enospc;
>>>> @@ -1737,6 +1740,8 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,
>>>>
>>>> sbi->total_valid_node_count--;
>>>> sbi->total_valid_block_count--;
>>>> + sbi->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>> + sbi->cur_reserved_blocks + 1);
>>>>
>>>> spin_unlock(&sbi->stat_lock);
>>>>
>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>> index 4c1bdcb..2934aa2 100644
>>>> --- a/fs/f2fs/super.c
>>>> +++ b/fs/f2fs/super.c
>>>> @@ -957,7 +957,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
>>>> buf->f_blocks = total_count - start_count;
>>>> buf->f_bfree = user_block_count - valid_user_blocks(sbi) + ovp_count;
>>>> buf->f_bavail = user_block_count - valid_user_blocks(sbi) -
>>>> - sbi->reserved_blocks;
>>>> + sbi->cur_reserved_blocks;
>>>>
>>>> avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
>>>>
>>>> @@ -2411,6 +2411,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>> le64_to_cpu(sbi->ckpt->valid_block_count);
>>>> sbi->last_valid_block_count = sbi->total_valid_block_count;
>>>> sbi->reserved_blocks = 0;
>>>> + sbi->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>> + sbi->user_block_count - sbi->total_valid_block_count);
>>>>
>>>> for (i = 0; i < NR_INODE_TYPE; i++) {
>>>> INIT_LIST_HEAD(&sbi->inode_list[i]);
>>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>>> index b769a3d..405c13f 100644
>>>> --- a/fs/f2fs/sysfs.c
>>>> +++ b/fs/f2fs/sysfs.c
>>>> @@ -76,6 +76,12 @@ static ssize_t lifetime_write_kbytes_show(struct f2fs_attr *a,
>>>> BD_PART_WRITTEN(sbi)));
>>>> }
>>>>
>>>> +static ssize_t cur_reserved_blocks_show(struct f2fs_attr *a,
>>>> + struct f2fs_sb_info *sbi, char *buf)
>>>> +{
>>>> + return snprintf(buf, PAGE_SIZE, "%u\n", sbi->cur_reserved_blocks);
>>>> +}
>>>> +
>>>> static ssize_t features_show(struct f2fs_attr *a,
>>>> struct f2fs_sb_info *sbi, char *buf)
>>>> {
>>>> @@ -143,12 +149,9 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>>> #endif
>>>> if (a->struct_type == RESERVED_BLOCKS) {
>>>> spin_lock(&sbi->stat_lock);
>>>> - if ((unsigned long)sbi->total_valid_block_count + t >
>>>> - (unsigned long)sbi->user_block_count) {
>>>> - spin_unlock(&sbi->stat_lock);
>>>> - return -EINVAL;
>>>> - }
>>>> *ui = t;
>>>> + sbi->cur_reserved_blocks = min(t, sbi->user_block_count -
>>>> + sbi->total_valid_block_count);
>>>> spin_unlock(&sbi->stat_lock);
>>>> return count;
>>>> }
>>>> @@ -274,6 +277,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
>>>> #endif
>>>> F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
>>>> F2FS_GENERAL_RO_ATTR(features);
>>>> +F2FS_GENERAL_RO_ATTR(cur_reserved_blocks);
>>>>
>>>> #ifdef CONFIG_F2FS_FS_ENCRYPTION
>>>> F2FS_FEATURE_RO_ATTR(encryption, FEAT_CRYPTO);
>>>> @@ -317,6 +321,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
>>>> ATTR_LIST(lifetime_write_kbytes),
>>>> ATTR_LIST(features),
>>>> ATTR_LIST(reserved_blocks),
>>>> + ATTR_LIST(cur_reserved_blocks),
>>>> NULL,
>>>> };
>>>>
>>>>
>>> .
>>>
>
> .
>

--
Thanks,
Yunlong Song


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