2013/4/29, Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>:
> Hi,
Hi. Jaegeuk.
>
> 2013-04-28 (일), 09:04 +0900, Namjae Jeon:
>> From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
>>
>> Few things can be changed in the default mkwrite function
>> 1) Make file_update_time at the start before acquiring any lock
>> 2) the condition page_offset(page) >= i_size_read(inode) should be
>> changed to page_offset(page) > i_size_read
>> 3) Move wait_on_page_writeback.
>>
>> Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
>> Signed-off-by: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
>> ---
>> fs/f2fs/file.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 5cc4dd8..dc76f9b 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -63,9 +63,10 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct
>> *vma,
>> f2fs_put_dnode(&dn);
>> mutex_unlock_op(sbi, ilock);
>>
>> + file_update_time(vma->vm_file);
>
> Should we update time even if error is occurred below?
Should we update time even if error is occurred below?
Even though the original time change position regarding
file_update_time is correct with respect to the failure conditions,
but we referred the code in other file systems.
We found that file_update_time in page fault is not critical part, so
first thing is to move this out of the locking.
We can see the following comment in block_page_mkwrite.
/*
* Update file times before taking page lock. We may end up failing the
* fault so this update may be superfluous but who really cares...
*/
Most filesystems use it regardless of below condition. Ext4 also does
this at the beginning of mkwrite-> just after
sb_start_pagefault(inode->i_sb);
>
>> lock_page(page);
>> if (page->mapping != inode->i_mapping ||
>> - page_offset(page) >= i_size_read(inode) ||
>> + page_offset(page) > i_size_read(inode) ||
>
> Why? IMO, there was no problem.
There is no problem and we could not find a test case either, but
looking at the code we thought it could be an alignment issue if due
to index, the page_offset() and i_size_read() ? may cause some
boundary condition.
The above changes were introduced without citing any issues, but just
to align the code.
So we can ignore this changed line :)
Thanks~
>
>> !PageUptodate(page)) {
>> unlock_page(page);
>> err = -EFAULT;
>> @@ -76,10 +77,7 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct
>> *vma,
>> * check to see if the page is mapped already (no holes)
>> */
>> if (PageMappedToDisk(page))
>> - goto out;
>> -
>> - /* fill the page */
>> - wait_on_page_writeback(page);
>> + goto mapped;
>>
>> /* page is wholly or partially inside EOF */
>> if (((page->index + 1) << PAGE_CACHE_SHIFT) > i_size_read(inode)) {
>> @@ -90,7 +88,9 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct
>> *vma,
>> set_page_dirty(page);
>> SetPageUptodate(page);
>>
>> - file_update_time(vma->vm_file);
>> +mapped:
>> + /* fill the page */
>> + wait_on_page_writeback(page);
>> out:
>> sb_end_pagefault(inode->i_sb);
>> return block_page_mkwrite_return(err);
>
> --
> Jaegeuk Kim
> Samsung
>
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