Re: [PATCH V5 14/16] xfs: Enable bulkstat ioctl to support 64-bit per-inode extent counters

Chandan Babu R
2022-02-07T06:18:21Z

On 02 Feb 2022 at 00:54, Darrick J. Wong wrote:
> On Fri, Jan 21, 2022 at 10:48:55AM +0530, Chandan Babu R wrote:
>> The following changes are made to enable userspace to obtain 64-bit extent
>> counters,
>> 1. Carve out a new 64-bit field xfs_bulkstat->bs_extents64 from
>> xfs_bulkstat->bs_pad[] to hold 64-bit extent counter.
>> 2. Define the new flag XFS_BULK_IREQ_BULKSTAT for userspace to indicate that
>> it is capable of receiving 64-bit extent counters.
>>
>> Suggested-by: Darrick J. Wong <djwong@kernel.org>
>> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
>> ---
>> fs/xfs/libxfs/xfs_fs.h | 12 ++++++++----
>> fs/xfs/xfs_ioctl.c | 3 +++
>> fs/xfs/xfs_itable.c | 27 +++++++++++++++++++++++++--
>> fs/xfs/xfs_itable.h | 7 ++++++-
>> fs/xfs/xfs_iwalk.h | 7 +++++--
>> 5 files changed, 47 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
>> index 42bc39501d81..4e12530eb518 100644
>> --- a/fs/xfs/libxfs/xfs_fs.h
>> +++ b/fs/xfs/libxfs/xfs_fs.h
>> @@ -393,7 +393,7 @@ struct xfs_bulkstat {
>> uint32_t bs_extsize_blks; /* extent size hint, blocks */
>>
>> uint32_t bs_nlink; /* number of links */
>> - uint32_t bs_extents; /* number of extents */
>> + uint32_t bs_extents; /* 32-bit data fork extent counter */
>> uint32_t bs_aextents; /* attribute number of extents */
>> uint16_t bs_version; /* structure version */
>> uint16_t bs_forkoff; /* inode fork offset in bytes */
>> @@ -402,8 +402,9 @@ struct xfs_bulkstat {
>> uint16_t bs_checked; /* checked inode metadata */
>> uint16_t bs_mode; /* type and mode */
>> uint16_t bs_pad2; /* zeroed */
>> + uint64_t bs_extents64; /* 64-bit data fork extent counter */
>>
>> - uint64_t bs_pad[7]; /* zeroed */
>> + uint64_t bs_pad[6]; /* zeroed */
>> };
>>
>> #define XFS_BULKSTAT_VERSION_V1 (1)
>> @@ -484,8 +485,11 @@ struct xfs_bulk_ireq {
>> */
>> #define XFS_BULK_IREQ_SPECIAL (1 << 1)
>>
>> -#define XFS_BULK_IREQ_FLAGS_ALL (XFS_BULK_IREQ_AGNO | \
>> - XFS_BULK_IREQ_SPECIAL)
>> +#define XFS_BULK_IREQ_NREXT64 (1 << 2)
>
> This needs a comment specifying the behavior of this flag.
>
> If the flag is set and the data fork extent count fits in both fields,
> will they both be filled out?

If the flag is set, xfs_bulkstat->bs_extents64 field will be assigned the data
fork extent count and xfs_bulkstat->bs_extents will be set to 0
(xfs_bulkstat() allocates xfs_bstat_chunk->buf by invoking kmem_zalloc()).

If the flag is not set, xfs_bulkstat->bs_extents field will be assigned the
data fork extent count and xfs_bulkstat->bs_extents64 will be set to 0.

>
> If the flag is set but the data fork extent count only fits in
> bs_extents64, what will be written to bs_extents?

bs_extents will be set to zero.

>
> If the flag is not set and the data fork extent count won't fit in
> bs_extents, do we return an error value? Fill it with garbage?
>

In this case, we return -EOVERFLOW and the contents of bs_extents will be set
to zero. This happens because xfs_bulkstat() will return success even if
xfs_iwalk() returned an error provided that we already have collected details
about one more inodes. The next call to xfs_ioc_bulkstat() will start from the
problematic inode. Here we allocate xfs_bstat_chunk->buf using kmem_zalloc()
which zeroes the contents of the allocated memory and returns -EOVERFLOW to
userspace.

>> +
>> +#define XFS_BULK_IREQ_FLAGS_ALL (XFS_BULK_IREQ_AGNO | \
>> + XFS_BULK_IREQ_SPECIAL | \
>> + XFS_BULK_IREQ_NREXT64)
>>
>> /* Operate on the root directory inode. */
>> #define XFS_BULK_IREQ_SPECIAL_ROOT (1)
>> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
>> index 29231a8c8a45..5d0781745a28 100644
>> --- a/fs/xfs/xfs_ioctl.c
>> +++ b/fs/xfs/xfs_ioctl.c
>> @@ -893,6 +893,9 @@ xfs_bulk_ireq_setup(
>> if (XFS_INO_TO_AGNO(mp, breq->startino) >= mp->m_sb.sb_agcount)
>> return -ECANCELED;
>>
>> + if (hdr->flags & XFS_BULK_IREQ_NREXT64)
>> + breq->flags |= XFS_IBULK_NREXT64;
>> +
>> return 0;
>> }
>>
>> diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
>> index c08c79d9e311..c9b44e8d0235 100644
>> --- a/fs/xfs/xfs_itable.c
>> +++ b/fs/xfs/xfs_itable.c
>> @@ -20,6 +20,7 @@
>> #include "xfs_icache.h"
>> #include "xfs_health.h"
>> #include "xfs_trans.h"
>> +#include "xfs_errortag.h"
>>
>> /*
>> * Bulk Stat
>> @@ -64,6 +65,7 @@ xfs_bulkstat_one_int(
>> struct xfs_inode *ip; /* incore inode pointer */
>> struct inode *inode;
>> struct xfs_bulkstat *buf = bc->buf;
>> + xfs_extnum_t nextents;
>> int error = -EINVAL;
>>
>> if (xfs_internal_inum(mp, ino))
>> @@ -102,7 +104,27 @@ xfs_bulkstat_one_int(
>>
>> buf->bs_xflags = xfs_ip2xflags(ip);
>> buf->bs_extsize_blks = ip->i_extsize;
>> - buf->bs_extents = xfs_ifork_nextents(&ip->i_df);
>> +
>> + nextents = xfs_ifork_nextents(&ip->i_df);
>> + if (!(bc->breq->flags & XFS_IBULK_NREXT64)) {
>> + xfs_extnum_t max_nextents = XFS_MAX_EXTCNT_DATA_FORK_OLD;
>> +
>> + if (unlikely(XFS_TEST_ERROR(false, mp,
>> + XFS_ERRTAG_REDUCE_MAX_IEXTENTS)))
>> + max_nextents = 10;
>> +
>> + if (nextents > max_nextents) {
>> + xfs_iunlock(ip, XFS_ILOCK_SHARED);
>> + xfs_irele(ip);
>> + error = -EOVERFLOW;
>> + goto out;
>> + }
>> +
>> + buf->bs_extents = nextents;
>> + } else {
>> + buf->bs_extents64 = nextents;
>> + }
>> +
>> xfs_bulkstat_health(ip, buf);
>> buf->bs_aextents = xfs_ifork_nextents(ip->i_afp);
>> buf->bs_forkoff = XFS_IFORK_BOFF(ip);
>> @@ -279,7 +301,8 @@ xfs_bulkstat(
>> if (error)
>> goto out;
>>
>> - error = xfs_iwalk(breq->mp, tp, breq->startino, breq->flags,
>> + error = xfs_iwalk(breq->mp, tp, breq->startino,
>> + breq->flags & XFS_IBULK_IWALK_MASK,
>
> I think it would be cleaner if this function did:
>
> unsigned int iwalk_flags = 0;
>
> if (breq->flags & XFS_IBULK_SAME_AG)
> iwalk_flags |= XFS_IWALK_SAME_AG;
>
> ...
>
> error = xfs_iwalk(breq->mp, tp, breq->startino, iwalk_flags,
> xfs_bulkstat_iwalk, breq->icount, &bc);
>
> to make the flags translation explicit. That enables a full cleanup
> of...
>
>> xfs_bulkstat_iwalk, breq->icount, &bc);
>> xfs_trans_cancel(tp);
>> out:
>> diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
>> index 7078d10c9b12..38f6900176a8 100644
>> --- a/fs/xfs/xfs_itable.h
>> +++ b/fs/xfs/xfs_itable.h
>> @@ -13,12 +13,17 @@ struct xfs_ibulk {
>> xfs_ino_t startino; /* start with this inode */
>> unsigned int icount; /* number of elements in ubuffer */
>> unsigned int ocount; /* number of records returned */
>> - unsigned int flags; /* see XFS_IBULK_FLAG_* */
>> + unsigned long long flags; /* see XFS_IBULK_FLAG_* */
>> };
>>
>> /* Only iterate within the same AG as startino */
>> #define XFS_IBULK_SAME_AG (XFS_IWALK_SAME_AG)
>>
>> +#define XFS_IBULK_ONLY_OFFSET 32
>> +#define XFS_IBULK_IWALK_MASK ((1ULL << XFS_IBULK_ONLY_OFFSET) - 1)
>> +
>> +#define XFS_IBULK_NREXT64 (1ULL << XFS_IBULK_ONLY_OFFSET)
>
> ...the code smells in the XFS_IBULK* flag space:
>
> /* Only iterate within the same AG as startino */
> #define XFS_IBULK_SAME_AG (1 << 0)
>
> /* Whatever it is that nrext64 does */
> #define XFS_IBULK_NREXT64 (1 << 31)
>

Ok. This will indeed make the code more readable. I will include this change
when I post the next version of this patch.

>> +
>> /*
>> * Advance the user buffer pointer by one record of the given size. If the
>> * buffer is now full, return the appropriate error code.
>> diff --git a/fs/xfs/xfs_iwalk.h b/fs/xfs/xfs_iwalk.h
>> index 37a795f03267..11be9dbb45c7 100644
>> --- a/fs/xfs/xfs_iwalk.h
>> +++ b/fs/xfs/xfs_iwalk.h
>> @@ -26,9 +26,12 @@ int xfs_iwalk_threaded(struct xfs_mount *mp, xfs_ino_t startino,
>> unsigned int inode_records, bool poll, void *data);
>>
>> /* Only iterate inodes within the same AG as @startino. */
>> -#define XFS_IWALK_SAME_AG (0x1)
>> +#define XFS_IWALK_SAME_AG (1 << 0)
>>
>> -#define XFS_IWALK_FLAGS_ALL (XFS_IWALK_SAME_AG)
>> +#define XFS_IWALK_NREXT64 (1 << 1)
>> +
>> +#define XFS_IWALK_FLAGS_ALL (XFS_IWALK_SAME_AG | \
>> + XFS_IWALK_NREXT64)
>
> XFS_IWALK_NREXT64 isn't used anywhere.
>

Sorry, I will remove this.

Thanks for all the review comments.

--
chandan