On 5/17/22 6:40 AM, Christian Brauner wrote:
> On Mon, May 16, 2022 at 09:47:09AM -0700, Stefan Roesch wrote:
>> This splits off the functions need_file_update_time() and
>> do_file_update_time() from the function file_update_time().
>>
>> This is required to support async buffered writes.
>> No intended functional changes in this patch.
>>
>> Signed-off-by: Stefan Roesch <shr@xxxxxx>
>> ---
>> fs/inode.c | 71 ++++++++++++++++++++++++++++++++++++------------------
>> 1 file changed, 47 insertions(+), 24 deletions(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index a6d70a1983f8..1d0b02763e98 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -2054,35 +2054,22 @@ int file_remove_privs(struct file *file)
>> }
>> EXPORT_SYMBOL(file_remove_privs);
>>
>> -/**
>> - * file_update_time - update mtime and ctime time
>> - * @file: file accessed
>> - *
>> - * Update the mtime and ctime members of an inode and mark the inode
>> - * for writeback. Note that this function is meant exclusively for
>> - * usage in the file write path of filesystems, and filesystems may
>> - * choose to explicitly ignore update via this function with the
>> - * S_NOCMTIME inode flag, e.g. for network filesystem where these
>> - * timestamps are handled by the server. This can return an error for
>> - * file systems who need to allocate space in order to update an inode.
>> - */
>> -
>> -int file_update_time(struct file *file)
>> +static int need_file_update_time(struct inode *inode, struct file *file,
>> + struct timespec64 *now)
>
> I think file_need_update_time() is easier to understand.
>
I renamed the function to file_needs_update_time().
>> {
>> - struct inode *inode = file_inode(file);
>> - struct timespec64 now;
>> int sync_it = 0;
>> - int ret;
>> +
>> + if (unlikely(file->f_mode & FMODE_NOCMTIME))
>> + return 0;
>
> Moving this into this generic helper and using the generic helper
> directly in file_update_atime() leads to a change in behavior for
> file_update_time() callers. Currently they'd get time settings updated
> even if FMODE_NOCMTIME is set but with this change they'd not get it
> updated anymore if FMODE_NOCMTIME is set. Am I reading this right?
>
Correct, this was not intended and will be addressed with the next version of the patch.
> Is this a bugfix? And if so it should be split into a separate commit...
>
>>
>> /* First try to exhaust all avenues to not sync */
>> if (IS_NOCMTIME(inode))
>> return 0;
>>
>> - now = current_time(inode);
>> - if (!timespec64_equal(&inode->i_mtime, &now))
>> + if (!timespec64_equal(&inode->i_mtime, now))
>> sync_it = S_MTIME;
>>
>> - if (!timespec64_equal(&inode->i_ctime, &now))
>> + if (!timespec64_equal(&inode->i_ctime, now))
>> sync_it |= S_CTIME;
>>
>> if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
>> @@ -2091,15 +2078,49 @@ int file_update_time(struct file *file)
>> if (!sync_it)
>> return 0;
>>
>> + return sync_it;
>> +}
>> +
>> +static int do_file_update_time(struct inode *inode, struct file *file,
>> + struct timespec64 *now, int sync_mode)
>> +{
>> + int ret;
>> +
>> /* Finally allowed to write? Takes lock. */
>> if (__mnt_want_write_file(file))
>> return 0;
>>
>> - ret = inode_update_time(inode, &now, sync_it);
>> + ret = inode_update_time(inode, now, sync_mode);
>> __mnt_drop_write_file(file);
>>
>> return ret;
>> }
>
> Maybe
>
> static int __file_update_time(struct inode *inode, struct file *file,
> struct timespec64 *now, int sync_mode)
> {
> int ret = 0;
>
> /* try to update time settings */
> if (!__mnt_want_write_file(file)) {
> ret = inode_update_time(inode, now, sync_mode);
> __mnt_drop_write_file(file);
> }
>
> return ret;
> }
>
> reads a little easier and the old comment is a bit confusing imho. I'd
> just say we keep it short.
>
I made the change.
>> +
>> +/**
>> + * file_update_time - update mtime and ctime time
>> + * @file: file accessed
>> + *
>> + * Update the mtime and ctime members of an inode and mark the inode
>> + * for writeback. Note that this function is meant exclusively for
>> + * usage in the file write path of filesystems, and filesystems may
>> + * choose to explicitly ignore update via this function with the
>> + * S_NOCMTIME inode flag, e.g. for network filesystem where these
>> + * timestamps are handled by the server. This can return an error for
>> + * file systems who need to allocate space in order to update an inode.
>> + */
>> +
>> +int file_update_time(struct file *file)
>
> My same lame complaint as before to make this kernel-doc. :)
>
> /**
> * file_update_time - update mtime and ctime time
> * @file: file accessed
> *
> * Update the mtime and ctime members of an inode and mark the inode or
> * writeback. Note that this function is meant exclusively for sage in
> * the file write path of filesystems, and filesystems may hoose to
> * explicitly ignore update via this function with the _NOCMTIME inode
> * flag, e.g. for network filesystem where these imestamps are handled
> * by the server. This can return an error for ile systems who need to
> * allocate space in order to update an inode.
> *
> * Return: 0 on success, negative errno on failure.
> */
> int file_update_time(struct file *file)
>
I added the above kernel documentation, I only fixed a couple of typos.
>> +{
>> + int err;
>> + struct inode *inode = file_inode(file);
>> + struct timespec64 now = current_time(inode);
>> +
>> + err = need_file_update_time(inode, file, &now);
>> + if (err < 0)
>> + return err;
>
> I may misread this but shouldn't this be err <= 0, i.e., if it returns 0
> then we don't need to update time?
>
Good catch. Fixed.
>> +
>> + return do_file_update_time(inode, file, &now, err);
>> +}
>> EXPORT_SYMBOL(file_update_time);
>>
>> /* Caller must hold the file's inode lock */
>> @@ -2108,6 +2129,7 @@ int file_modified(struct file *file)
>> int ret;
>> struct dentry *dentry = file_dentry(file);
>> struct inode *inode = file_inode(file);
>> + struct timespec64 now = current_time(inode);
>>
>> /*
>> * Clear the security bits if the process is not being run by root.
>> @@ -2122,10 +2144,11 @@ int file_modified(struct file *file)
>> return ret;
>> }
>>
>> - if (unlikely(file->f_mode & FMODE_NOCMTIME))
>> - return 0;
>> + ret = need_file_update_time(inode, file, &now);
>> + if (ret <= 0)
>> + return ret;
>>
>> - return file_update_time(file);
>> + return do_file_update_time(inode, file, &now, ret);
>> }
>> EXPORT_SYMBOL(file_modified);
>>
>> --
>> 2.30.2
>>
