Re: [PATCH 7/9] xfs: Add attr context to log item

Brian Foster
2019-04-22T13:03:44Z

On Fri, Apr 12, 2019 at 03:50:34PM -0700, Allison Henderson wrote:
> This patch modifies xfs_attr_item to store a xfs_da_args, a xfs_buf pointer
> and a new state type. We will use these in the next patch when
> we modify xfs_set_attr_args to roll transactions by returning EAGAIN.
> Because the subroutines of this function modify the contents of these
> structures, we need to find a place to store them where they remain
> instantiated across multiple calls to xfs_set_attr_args.
>
> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> ---

I see Darrick has already commented on the whole state thing. I'll
probably have to grok the next patch to comment further, but just a
couple initial thoughts:

First, I hit a build failure with this patch. It looks like there's a
missed include in the scrub code:

...
CC [M] fs/xfs/scrub/repair.o
In file included from fs/xfs/scrub/repair.c:32:
fs/xfs/libxfs/xfs_attr.h:105:21: error: field ‘xattri_args’ has incomplete type
struct xfs_da_args xattri_args; /* args context */
...

Second, the commit log suggests that the states will reflect the current
transaction roll points (i.e., establishing re-entry points down in
xfs_attr_set_args(). I'm kind of wondering if we should break these
xattr set sub-sequences down into smaller helper functions (refactoring
the existing code as we go) such that the mechanism could technically be
used deferred or not. Re: the previous thought on whether to defer xattr
removes or not, there might also be cases where there's not a need to
defer xattr sets.

E.g., taking a quick peek into the next patch, the state 1 case in
xfs_attr_try_sf_addname() is actually a transaction commit, which I
think means we're done. We'd have done an attr memory allocation,
deferred op and transaction roll where none was necessary so it might
not be worth it to defer in that scenario. Hmm, it also looks like we
return -EAGAIN in places where we've not actually done any work, like if
a shortform add attempt returns -ENOSPC (or the -EAGAIN return before we
even attempt the sf add). That kind of looks like a waste of transaction
rolls and further suggests it might be cleaner to break this whole path
down into helpers and put it back together in a way more conducive to
deferred operations.

Brian

> fs/xfs/libxfs/xfs_attr.h | 18 +++++++++++++++++-
> fs/xfs/scrub/common.c | 2 ++
> fs/xfs/xfs_acl.c | 2 ++
> fs/xfs/xfs_attr_item.c | 2 +-
> fs/xfs/xfs_ioctl.c | 2 ++
> fs/xfs/xfs_ioctl32.c | 2 ++
> fs/xfs/xfs_iops.c | 1 +
> fs/xfs/xfs_xattr.c | 1 +
> 8 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index 974c963..4ce3b0a 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -77,6 +77,13 @@ typedef struct attrlist_ent { /* data from attr_list() */
> char a_name[1]; /* attr name (NULL terminated) */
> } attrlist_ent_t;
>
> +/* Attr state machine types */
> +enum xfs_attr_state {
> + XFS_ATTR_STATE1 = 1,
> + XFS_ATTR_STATE2 = 2,
> + XFS_ATTR_STATE3 = 3,
> +};
> +
> /*
> * List of attrs to commit later.
> */
> @@ -88,7 +95,16 @@ struct xfs_attr_item {
> void *xattri_name; /* attr name */
> uint32_t xattri_name_len; /* length of name */
> uint32_t xattri_flags; /* attr flags */
> - struct list_head xattri_list;
> +
> + /*
> + * Delayed attr parameters that need to remain instantiated
> + * across transaction rolls during the defer finish
> + */
> + struct xfs_buf *xattri_leaf_bp; /* Leaf buf to release */
> + enum xfs_attr_state xattri_state; /* state machine marker */
> + struct xfs_da_args xattri_args; /* args context */
> +
> + struct list_head xattri_list;
>
> /*
> * A byte array follows the header containing the file name and
> diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
> index 0c54ff5..270c32e 100644
> --- a/fs/xfs/scrub/common.c
> +++ b/fs/xfs/scrub/common.c
> @@ -30,6 +30,8 @@
> #include "xfs_rmap_btree.h"
> #include "xfs_log.h"
> #include "xfs_trans_priv.h"
> +#include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_reflink.h"
> #include "scrub/xfs_scrub.h"
> diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
> index 142de8d..9b1b93e 100644
> --- a/fs/xfs/xfs_acl.c
> +++ b/fs/xfs/xfs_acl.c
> @@ -10,6 +10,8 @@
> #include "xfs_mount.h"
> #include "xfs_inode.h"
> #include "xfs_acl.h"
> +#include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_trace.h"
> #include <linux/slab.h>
> diff --git a/fs/xfs/xfs_attr_item.c b/fs/xfs/xfs_attr_item.c
> index 0ea19b4..36e6d1e 100644
> --- a/fs/xfs/xfs_attr_item.c
> +++ b/fs/xfs/xfs_attr_item.c
> @@ -19,10 +19,10 @@
> #include "xfs_rmap.h"
> #include "xfs_inode.h"
> #include "xfs_icache.h"
> -#include "xfs_attr.h"
> #include "xfs_shared.h"
> #include "xfs_da_format.h"
> #include "xfs_da_btree.h"
> +#include "xfs_attr.h"
>
> static inline struct xfs_attri_log_item *ATTRI_ITEM(struct xfs_log_item *lip)
> {
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index ab341d6..c8728ca 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -16,6 +16,8 @@
> #include "xfs_rtalloc.h"
> #include "xfs_itable.h"
> #include "xfs_error.h"
> +#include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_bmap.h"
> #include "xfs_bmap_util.h"
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index 5001dca..23f6990 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -21,6 +21,8 @@
> #include "xfs_fsops.h"
> #include "xfs_alloc.h"
> #include "xfs_rtalloc.h"
> +#include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_ioctl.h"
> #include "xfs_ioctl32.h"
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index e73c21a..561c467 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -17,6 +17,7 @@
> #include "xfs_acl.h"
> #include "xfs_quota.h"
> #include "xfs_error.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_trans.h"
> #include "xfs_trace.h"
> diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> index 3013746..938e81d 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -11,6 +11,7 @@
> #include "xfs_mount.h"
> #include "xfs_da_format.h"
> #include "xfs_inode.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_attr_leaf.h"
> #include "xfs_acl.h"
> --
> 2.7.4
>