On Fri, Jun 16, 2017 at 10:59:32AM -0700, Darrick J. Wong wrote:
> Check the inode cache for a particular inode number. If it's in the
> cache, check that it's not currently being reclaimed. If it's not being
> reclaimed, return zero if the inode is allocated. This function will be
> used by various scrubbers to decide if the cache is more up to date
> than the disk in terms of checking if an inode is allocated.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> v3: plumb in an opportunistic "get it from the cache" flag to _iget
> and refactor the helper to use it.
> ---
> fs/xfs/xfs_icache.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++--
> fs/xfs/xfs_icache.h | 4 ++++
> 2 files changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index f61c84f8..45845b7 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -369,6 +369,11 @@ xfs_iget_cache_hit(
> if (ip->i_flags & XFS_IRECLAIMABLE) {
> trace_xfs_iget_reclaim(ip);
>
> + if (flags & XFS_IGET_INCORE) {
> + error = -EAGAIN;
> + goto out_error;
> + }
> +
> /*
> * We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
> * from stomping over us while we recycle the inode. We can't
> @@ -433,7 +438,8 @@ xfs_iget_cache_hit(
> if (lock_flags != 0)
> xfs_ilock(ip, lock_flags);
>
> - xfs_iflags_clear(ip, XFS_ISTALE | XFS_IDONTCACHE);
> + if (!(flags & XFS_IGET_INCORE))
> + xfs_iflags_clear(ip, XFS_ISTALE | XFS_IDONTCACHE);
> XFS_STATS_INC(mp, xs_ig_found);
>
> return 0;
> @@ -604,6 +610,10 @@ xfs_iget(
It might be a good idea to check (or assert) that _IGET_INCORE isn't
specified with any other flags that don't make sense. Otherwise this
looks good to me, thanks...
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> goto out_error_or_again;
> } else {
> rcu_read_unlock();
> + if (flags & XFS_IGET_INCORE) {
> + error = -ENOENT;
> + goto out_error_or_again;
> + }
> XFS_STATS_INC(mp, xs_ig_missed);
>
> error = xfs_iget_cache_miss(mp, pag, tp, ino, &ip,
> @@ -624,7 +634,7 @@ xfs_iget(
> return 0;
>
> out_error_or_again:
> - if (error == -EAGAIN) {
> + if (!(flags & XFS_IGET_INCORE) && error == -EAGAIN) {
> delay(1);
> goto again;
> }
> @@ -633,6 +643,44 @@ xfs_iget(
> }
>
> /*
> + * "Is this a cached inode that's also allocated?"
> + *
> + * Look up an inode by number in the given file system. If the inode is
> + * in cache and isn't in purgatory, return 1 if the inode is allocated
> + * and 0 if it is not. For all other cases (not in cache, being torn
> + * down, etc.), return a negative error code.
> + *
> + * The caller has to prevent inode allocation and freeing activity,
> + * presumably by locking the AGI buffer. This is to ensure that an
> + * inode cannot transition from allocated to freed until the caller is
> + * ready to allow that. If the inode is in an intermediate state (new,
> + * reclaimable, or being reclaimed), -EAGAIN will be returned; if the
> + * inode is not in the cache, -ENOENT will be returned. The caller must
> + * deal with these scenarios appropriately.
> + *
> + * This is a specialized use case for the online scrubber; if you're
> + * reading this, you probably want xfs_iget.
> + */
> +int
> +xfs_icache_inode_is_allocated(
> + struct xfs_mount *mp,
> + struct xfs_trans *tp,
> + xfs_ino_t ino,
> + bool *inuse)
> +{
> + struct xfs_inode *ip;
> + int error;
> +
> + error = xfs_iget(mp, tp, ino, XFS_IGET_INCORE, 0, &ip);
> + if (error)
> + return error;
> +
> + *inuse = !!(VFS_I(ip)->i_mode);
> + IRELE(ip);
> + return 0;
> +}
> +
> +/*
> * The inode lookup is done in batches to keep the amount of lock traffic and
> * radix tree lookups to a minimum. The batch size is a trade off between
> * lookup reduction and stack usage. This is in the reclaim path, so we can't
> diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h
> index 9183f77..bff4d85 100644
> --- a/fs/xfs/xfs_icache.h
> +++ b/fs/xfs/xfs_icache.h
> @@ -47,6 +47,7 @@ struct xfs_eofblocks {
> #define XFS_IGET_CREATE 0x1
> #define XFS_IGET_UNTRUSTED 0x2
> #define XFS_IGET_DONTCACHE 0x4
> +#define XFS_IGET_INCORE 0x8 /* don't read from disk or reinit */
>
> /*
> * flags for AG inode iterator
> @@ -126,4 +127,7 @@ xfs_fs_eofblocks_from_user(
> return 0;
> }
>
> +int xfs_icache_inode_is_allocated(struct xfs_mount *mp, struct xfs_trans *tp,
> + xfs_ino_t ino, bool *inuse);
> +
> #endif
> --
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