Re: [PATCH V7 15/17] xfs: Enable bulkstat ioctl to support 64-bit per-inode extent counters

Chandan Babu R
2022-03-05T12:45:55Z

On 04 Mar 2022 at 13:39, Dave Chinner wrote:
> On Tue, Mar 01, 2022 at 04:09:36PM +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 | 20 ++++++++++++++++----
>> fs/xfs/xfs_ioctl.c | 3 +++
>> fs/xfs/xfs_itable.c | 30 ++++++++++++++++++++++++++++--
>> fs/xfs/xfs_itable.h | 4 +++-
>> fs/xfs/xfs_iwalk.h | 2 +-
>> 5 files changed, 51 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
>> index 2204d49d0c3a..31ccbff2f16c 100644
>> --- a/fs/xfs/libxfs/xfs_fs.h
>> +++ b/fs/xfs/libxfs/xfs_fs.h
>> @@ -378,7 +378,7 @@ 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 */
>> @@ -387,8 +387,9 @@ 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)
>> @@ -469,8 +470,19 @@ 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)
>> +/*
>> + * Return data fork extent count via xfs_bulkstat->bs_extents64 field and assign
>> + * 0 to xfs_bulkstat->bs_extents when the flag is set. Otherwise, use
>> + * xfs_bulkstat->bs_extents for returning data fork extent count and set
>> + * xfs_bulkstat->bs_extents64 to 0. In the second case, return -EOVERFLOW and
>> + * assign 0 to xfs_bulkstat->bs_extents if data fork extent count is larger than
>> + * XFS_MAX_EXTCNT_DATA_FORK_OLD.
>> + */
>> +#define XFS_BULK_IREQ_NREXT64 (1 << 2)
>> +
>> +#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 2515fe8299e1..22947c5ffd34 100644
>> --- a/fs/xfs/xfs_ioctl.c
>> +++ b/fs/xfs/xfs_ioctl.c
>> @@ -813,6 +813,9 @@ 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..0272a3c9d8b1 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;
>> + }
>
> This just seems wrong. This will cause a total abort of the bulkstat
> pass which will just be completely unexpected by any application
> taht does not know about 64 bit extent counts. Most of them likely
> don't even care about the extent count in the data being returned.
>
> Really, I think this should just set the extent count to the MAX
> number and just continue onwards, otherwise existing application
> will not be able to bulkstat a filesystem with large extents counts
> in it at all.
>

Actually, I don't know much about how applications use bulkstat. I am
dependent on guidance from other developers who are well versed on this
topic. I will change the code to return maximum extent count if the value
overflows older extent count limits.

>> @@ -256,6 +278,7 @@ xfs_bulkstat(
>> .breq = breq,
>> };
>> struct xfs_trans *tp;
>> + unsigned int iwalk_flags = 0;
>> int error;
>>
>> if (breq->mnt_userns != &init_user_ns) {
>> @@ -279,7 +302,10 @@ xfs_bulkstat(
>> if (error)
>> goto out;
>>
>> - error = xfs_iwalk(breq->mp, tp, breq->startino, breq->flags,
>> + 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);
>> xfs_trans_cancel(tp);
>> out:
>
> This looks like an unrelated bug fix and doesn't make any sense in
> the context of the change being made in this patch.
>

You are right. This is about removing dependency of XFS_IBULK_* flags from
XFS_IWALK_* flags. I will include this change in a separate patch.

>> diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
>> index 7078d10c9b12..9223529cd7bd 100644
>> --- a/fs/xfs/xfs_itable.h
>> +++ b/fs/xfs/xfs_itable.h
>> @@ -17,7 +17,9 @@ struct xfs_ibulk {
>> };
>>
>> /* Only iterate within the same AG as startino */
>> -#define XFS_IBULK_SAME_AG (XFS_IWALK_SAME_AG)
>> +#define XFS_IBULK_SAME_AG (1ULL << 0)
>> +
>> +#define XFS_IBULK_NREXT64 (1ULL << 1)
>
> Why are these defined as ULL? AFAICT they are only ever stored in an
> unsigned int.
>

In one of the older versions of the patchset, I had extended xfs_ibulk->flags
to an "unsigned long long" field. These changes are remnants from the older
version. I will remove ULL suffix.

>>
>> /*
>> * Advance the user buffer pointer by one record of the given size. If the
>> diff --git a/fs/xfs/xfs_iwalk.h b/fs/xfs/xfs_iwalk.h
>> index 37a795f03267..3a68766fd909 100644
>> --- a/fs/xfs/xfs_iwalk.h
>> +++ b/fs/xfs/xfs_iwalk.h
>> @@ -26,7 +26,7 @@ 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)
>
> This also seems unrelated. If these flags need changing, can you
> pull it out into a separate patch explaining the what and why it
> needs changing because I'm getting lost in the 3-layer-deep (or is
> it 4?) iwalk/ibulk/ibulkreq flag munging that is all intertwined in
> this patch....
>

Sorry about that. As I had mentioned earlier, this is about removing
dependency of XFS_IBULK_* flags from XFS_IWALK_* flags. I will include this
change in a separate patch.

--
chandan