Re: [PATCH V3 05/12] xfs: Introduce xfs_dfork_nextents() helper

Chandan Babu R
2021-09-28T09:47:20Z

On 28 Sep 2021 at 04:16, Dave Chinner wrote:
> On Thu, Sep 16, 2021 at 03:36:40PM +0530, Chandan Babu R wrote:
>> This commit replaces the macro XFS_DFORK_NEXTENTS() with the helper function
>> xfs_dfork_nextents(). As of this commit, xfs_dfork_nextents() returns the same
>> value as XFS_DFORK_NEXTENTS(). A future commit which extends inode's extent
>> counter fields will add more logic to this helper.
>>
>> This commit also replaces direct accesses to xfs_dinode->di_[a]nextents
>> with calls to xfs_dfork_nextents().
>>
>> No functional changes have been made.
>>
>> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
>> ---
>> fs/xfs/libxfs/xfs_format.h | 28 +++++++++++++++++++++----
>> fs/xfs/libxfs/xfs_inode_buf.c | 16 +++++++++-----
>> fs/xfs/libxfs/xfs_inode_fork.c | 10 +++++----
>> fs/xfs/scrub/inode.c | 18 +++++++++-------
>> fs/xfs/scrub/inode_repair.c | 38 +++++++++++++++++++++-------------
>> 5 files changed, 75 insertions(+), 35 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
>> index ed8a5354bcbf..b4638052801f 100644
>> --- a/fs/xfs/libxfs/xfs_format.h
>> +++ b/fs/xfs/libxfs/xfs_format.h
>> @@ -930,10 +930,30 @@ enum xfs_dinode_fmt {
>> ((w) == XFS_DATA_FORK ? \
>> (dip)->di_format : \
>> (dip)->di_aformat)
>> -#define XFS_DFORK_NEXTENTS(dip,w) \
>> - ((w) == XFS_DATA_FORK ? \
>> - be32_to_cpu((dip)->di_nextents) : \
>> - be16_to_cpu((dip)->di_anextents))
>> +
>> +static inline xfs_extnum_t
>> +xfs_dfork_nextents(
>> + struct xfs_dinode *dip,
>> + int whichfork)
>> +{
>> + xfs_extnum_t nextents = 0;
>> +
>> + switch (whichfork) {
>> + case XFS_DATA_FORK:
>> + nextents = be32_to_cpu(dip->di_nextents);
>> + break;
>> +
>
> No need for whitespace line after the break, and this could just
> return the value directly.
>

Ok. I will fix this.

>> + case XFS_ATTR_FORK:
>> + nextents = be16_to_cpu(dip->di_anextents);
>> + break;
>> +
>> + default:
>> + ASSERT(0);
>> + break;
>> + }
>> +
>> + return nextents;
>> +}
>
> I think that all the conditional inode fork macros
> should be moved to libxfs/xfs_inode_fork.h as they are converted.
>
> These macros are not acutally part of the on-disk format definition
> (which is what xfs_format.h is supposed to contain) - it's code that
> parses the on-disk format and that is supposed to be in
> libxfs/xfs_inode_fork.[ch]....
>
> Next thing: the caller almost always knows what fork it wants
> the extents for - only 3 callers have a whichfork variable. So,
> perhaps:
>
> static inline xfs_extnum_t
> xfs_dfork_data_extents(
> struct xfs_dinode *dip)
> {
> return be32_to_cpu(dip->di_nextents);
> }
>
> static inline xfs_extnum_t
> xfs_dfork_attr_extents(
> struct xfs_dinode *dip)
> {
> return be16_to_cpu(dip->di_anextents);
> }
>
> static inline xfs_extnum_t
> xfs_dfork_extents(
> struct xfs_dinode *dip,
> int whichfork)
> {
> switch (whichfork) {
> case XFS_DATA_FORK:
> return xfs_dfork_data_extents(dip);
> case XFS_ATTR_FORK:
> return xfs_dfork_attr_extents(dip);
> default:
> ASSERT(0);
> break;
> }
> return 0;
> }
>
> So we don't have to rely on the compiler optimising away the switch
> statement correctly to produce optimal code.
>

I will fix this too.

>> --- a/fs/xfs/libxfs/xfs_inode_buf.c
>> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
>> @@ -342,9 +342,11 @@ xfs_dinode_verify_fork(
>> struct xfs_mount *mp,
>> int whichfork)
>> {
>> - xfs_extnum_t di_nextents = XFS_DFORK_NEXTENTS(dip, whichfork);
>> + xfs_extnum_t di_nextents;
>> xfs_extnum_t max_extents;
>>
>> + di_nextents = xfs_dfork_nextents(dip, whichfork);
>> +
>> switch (XFS_DFORK_FORMAT(dip, whichfork)) {
>> case XFS_DINODE_FMT_LOCAL:
>> /*
>> @@ -474,6 +476,8 @@ xfs_dinode_verify(
>> uint16_t flags;
>> uint64_t flags2;
>> uint64_t di_size;
>> + xfs_extnum_t nextents;
>> + xfs_rfsblock_t nblocks;
>
> That's a block number type, not a block count:
>
> typedef uint64_t xfs_rfsblock_t; /* blockno in filesystem (raw) */
> ....
> typedef uint64_t xfs_filblks_t; /* number of blocks in a file */
>
> The latter is the appropriate type to use here.
>
> Oh, the struct xfs_inode and the struct xfs_log_dinode makes
> this same type mistake. Ok, that's a cleanup for another day....
>

I will add this cleanup to my todo list.

--
chandan