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Date: Wed, 31 Jul 2013 18:09:49 +0800
From: Gu Zheng <guz.fnst@...fujitsu.com>
To: jaegeuk.kim@...sung.com
CC: f2fs <linux-f2fs-devel@...ts.sourceforge.net>,
fsdevel <linux-fsdevel@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: add a wait step when submit bio with {READ,WRITE}_SYNC
On 07/31/2013 06:06 PM, Jaegeuk Kim wrote:
> 2013-07-31 (수), 09:59 +0800, Gu Zheng:
>> Hi Kim,
>>
>> On 07/30/2013 08:29 PM, Jaegeuk Kim wrote:
>>
>>> Hi Gu,
>>>
>>> The original read flow was to avoid redandunt lock/unlock_page() calls.
>>
>> Right, this can gain better read performance. But is the wait step after
>> submitting bio with READ_SYNC needless too?
>
> Correct, the READ_SYNC is also used for IO priority.
> The basic read policy here is that the caller should lock the page only
> when it wants to manipulate there-in data.
> Otherwise, we don't need to unnecessary lock and unlocks.
Got it, it seems that I had some miss reading originally, it's
clear now, thanks very much for your explanation.:)
Regards,
Gu
> Thanks,
>
>>
>>> And we should not wait for WRITE_SYNC, since it is just for write
>>> priority, not for synchronization of the file system.
>>
>> Got it, thanks for your explanation.:)
>>
>> Best regards,
>> Gu
>>
>>> Thanks,
>>>
>>> 2013-07-30 (화), 18:06 +0800, Gu Zheng:
>>>> When we submit bio with READ_SYNC or WRITE_SYNC, we need to wait a
>>>> moment for the io completion, current codes only find_data_page() follows the
>>>> rule, other places missing this step, so add it.
>>>>
>>>> Further more, moving the PageUptodate check into f2fs_readpage() to clean up
>>>> the codes.
>>>>
>>>> Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
>>>> ---
>>>> fs/f2fs/checkpoint.c | 1 -
>>>> fs/f2fs/data.c | 39 +++++++++++++++++----------------------
>>>> fs/f2fs/node.c | 1 -
>>>> fs/f2fs/recovery.c | 2 --
>>>> fs/f2fs/segment.c | 2 +-
>>>> 5 files changed, 18 insertions(+), 27 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>> index fe91773..e376a42 100644
>>>> --- a/fs/f2fs/checkpoint.c
>>>> +++ b/fs/f2fs/checkpoint.c
>>>> @@ -64,7 +64,6 @@ repeat:
>>>> if (f2fs_readpage(sbi, page, index, READ_SYNC))
>>>> goto repeat;
>>>>
>>>> - lock_page(page);
>>>> if (page->mapping != mapping) {
>>>> f2fs_put_page(page, 1);
>>>> goto repeat;
>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>> index 19cd7c6..b048936 100644
>>>> --- a/fs/f2fs/data.c
>>>> +++ b/fs/f2fs/data.c
>>>> @@ -216,13 +216,11 @@ struct page *find_data_page(struct inode *inode, pgoff_t index, bool sync)
>>>>
>>>> err = f2fs_readpage(sbi, page, dn.data_blkaddr,
>>>> sync ? READ_SYNC : READA);
>>>> - if (sync) {
>>>> - wait_on_page_locked(page);
>>>> - if (!PageUptodate(page)) {
>>>> - f2fs_put_page(page, 0);
>>>> - return ERR_PTR(-EIO);
>>>> - }
>>>> - }
>>>> + if (err)
>>>> + return ERR_PTR(err);
>>>> +
>>>> + if (sync)
>>>> + unlock_page(page);
>>>> return page;
>>>> }
>>>>
>>>> @@ -267,11 +265,6 @@ repeat:
>>>> if (err)
>>>> return ERR_PTR(err);
>>>>
>>>> - lock_page(page);
>>>> - if (!PageUptodate(page)) {
>>>> - f2fs_put_page(page, 1);
>>>> - return ERR_PTR(-EIO);
>>>> - }
>>>> if (page->mapping != mapping) {
>>>> f2fs_put_page(page, 1);
>>>> goto repeat;
>>>> @@ -325,11 +318,7 @@ repeat:
>>>> err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
>>>> if (err)
>>>> return ERR_PTR(err);
>>>> - lock_page(page);
>>>> - if (!PageUptodate(page)) {
>>>> - f2fs_put_page(page, 1);
>>>> - return ERR_PTR(-EIO);
>>>> - }
>>>> +
>>>> if (page->mapping != mapping) {
>>>> f2fs_put_page(page, 1);
>>>> goto repeat;
>>>> @@ -399,6 +388,16 @@ int f2fs_readpage(struct f2fs_sb_info *sbi, struct page *page,
>>>>
>>>> submit_bio(type, bio);
>>>> up_read(&sbi->bio_sem);
>>>> +
>>>> + if (type == READ_SYNC) {
>>>> + wait_on_page_locked(page);
>>>> + lock_page(page);
>>>> + if (!PageUptodate(page)) {
>>>> + f2fs_put_page(page, 1);
>>>> + return -EIO;
>>>> + }
>>>> + }
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>> @@ -679,11 +678,7 @@ repeat:
>>>> err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
>>>> if (err)
>>>> return err;
>>>> - lock_page(page);
>>>> - if (!PageUptodate(page)) {
>>>> - f2fs_put_page(page, 1);
>>>> - return -EIO;
>>>> - }
>>>> +
>>>> if (page->mapping != mapping) {
>>>> f2fs_put_page(page, 1);
>>>> goto repeat;
>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>> index f5172e2..f061554 100644
>>>> --- a/fs/f2fs/node.c
>>>> +++ b/fs/f2fs/node.c
>>>> @@ -1534,7 +1534,6 @@ int restore_node_summary(struct f2fs_sb_info *sbi,
>>>> if (f2fs_readpage(sbi, page, addr, READ_SYNC))
>>>> goto out;
>>>>
>>>> - lock_page(page);
>>>> rn = F2FS_NODE(page);
>>>> sum_entry->nid = rn->footer.nid;
>>>> sum_entry->version = 0;
>>>> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
>>>> index 639eb34..ec68183 100644
>>>> --- a/fs/f2fs/recovery.c
>>>> +++ b/fs/f2fs/recovery.c
>>>> @@ -140,8 +140,6 @@ static int find_fsync_dnodes(struct f2fs_sb_info *sbi, struct list_head *head)
>>>> if (err)
>>>> goto out;
>>>>
>>>> - lock_page(page);
>>>> -
>>>> if (cp_ver != cpver_of_node(page))
>>>> break;
>>>>
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index 9b74ae2..bcd19db 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -639,7 +639,7 @@ static void do_submit_bio(struct f2fs_sb_info *sbi,
>>>>
>>>> trace_f2fs_do_submit_bio(sbi->sb, btype, sync, sbi->bio[btype]);
>>>>
>>>> - if (type == META_FLUSH) {
>>>> + if ((type == META_FLUSH) || (rw & WRITE_SYNC)) {
>>>> DECLARE_COMPLETION_ONSTACK(wait);
>>>> p->is_sync = true;
>>>> p->wait = &wait;
>>>
>>
>>
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