Re: [PATCH v4 03/11] fs: Initial atomic write support

John Garry
2024-02-26T08:52:03Z

...

>>
>> Helper function atomic_write_valid() can be used by FSes to verify
>> compliant writes.
>>
>> Signed-off-by: Prasad Singamsetty <prasad.singamsetty@oracle.com>
>> #jpg: merge into single patch and much rewrite
>
> ^^^ this might be a miss I guess.

I'm not sure what you mean. Here I am just briefly commenting on much
changes which I made.

>
>> Signed-off-by: John Garry <john.g.garry@oracle.com>
>> ---
>> fs/aio.c | 8 ++++----
>> fs/btrfs/ioctl.c | 2 +-
>> fs/read_write.c | 2 +-
>> include/linux/fs.h | 36 +++++++++++++++++++++++++++++++++++-
>> include/uapi/linux/fs.h | 5 ++++-
>> io_uring/rw.c | 4 ++--
>> 6 files changed, 47 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/aio.c b/fs/aio.c
>> index bb2ff48991f3..21bcbc076fd0 100644
>> --- a/fs/aio.c
>> +++ b/fs/aio.c
>> @@ -1502,7 +1502,7 @@ static void aio_complete_rw(struct kiocb *kiocb, long res)
>> iocb_put(iocb);
>> }
>>
>> -static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
>> +static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb, int type)
>
> maybe rw_type?

ok

>
>> {
>> int ret;
>>
>> @@ -1528,7 +1528,7 @@ static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
>> } else

...

>> +
>> /* 32bit hashes as llseek() offset (for directories) */
>> #define FMODE_32BITHASH ((__force fmode_t)0x200)
>> /* 64bit hashes as llseek() offset (for directories) */
>> @@ -328,6 +333,7 @@ enum rw_hint {
>> #define IOCB_SYNC (__force int) RWF_SYNC
>> #define IOCB_NOWAIT (__force int) RWF_NOWAIT
>> #define IOCB_APPEND (__force int) RWF_APPEND
>> +#define IOCB_ATOMIC (__force int) RWF_ATOMIC
>>
>
> You might also want to add this definition in here too
>
> #define TRACE_IOCB_STRINGS \
> <...>
> <...>
> { IOCB_ATOMIC, "ATOMIC" }

ok

I suppose that new flag RWF_NOAPPEND in linux-next also should have this

>>
>> +static inline bool atomic_write_valid(loff_t pos, struct iov_iter *iter,
>> + unsigned int unit_min, unsigned int unit_max)
>> +{
>> + size_t len = iov_iter_count(iter);
>> +
>> + if (!iter_is_ubuf(iter))
>> + return false;
>
> There is no mention about this limitation in the commit message of this
> patch. Maybe it will be good to capture why this limitation to only
> support ubuf and/or any plans to lift this restriction in future
> in the commit message?

ok, I can mention this in the commit message.

>
>
>> +
>> + if (len == unit_min || len == unit_max) {
>> + /* ok if exactly min or max */
>> + } else if (len < unit_min || len > unit_max) {
>> + return false;
>> + } else if (!is_power_of_2(len)) {
>> + return false;
>> + }
>
> Checking for len == unit_min || len == unit_max is redundant when
> unit_min and unit_max are already power of 2.

Sure, but it was an optimization, considering that typically we will be
issuing unit_max in anticipated FS scenario.

Anyway, I will be changing this according to an earlier comment.

Thanks,
John