Re: [PATCH v5 13/14] xfs: Add delay ready attr remove routines

Brian Foster
2019-12-13T20:39:49Z

On Wed, Dec 11, 2019 at 09:15:12PM -0700, Allison Collins wrote:
> This patch modifies the attr remove routines to be delay ready. This
> means they no longer roll or commit transactions, but instead return
> -EAGAIN to have the calling routine roll and refresh the transaction.
> In this series, xfs_attr_remove_args has become
> xfs_attr_remove_iter, which uses a sort of state machine like switch
> to keep track of where it was when EAGAIN was returned.
> xfs_attr_node_removename has also been modified to use the switch,
> and a new version of xfs_attr_remove_args consists of a simple loop
> to refresh the transaction until the operation is completed.
>
> This patch also adds a new struct xfs_delattr_context, which we will
> use to keep track of the current state of an attribute operation.
> The new xfs_delattr_state enum is used to track various operations
> that are in progress so that we know not to repeat them, and resume
> where we left off before EAGAIN was returned to cycle out the
> transaction. Other members take the place of local variables that
> need to retain their values across multiple function recalls.
>
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
> fs/xfs/libxfs/xfs_attr.c | 127 ++++++++++++++++++++++++++++++++++++-------
> fs/xfs/libxfs/xfs_attr.h | 1 +
> fs/xfs/libxfs/xfs_da_btree.h | 16 ++++++
> fs/xfs/scrub/common.c | 2 +
> fs/xfs/xfs_acl.c | 2 +
> fs/xfs/xfs_attr_list.c | 1 +
> fs/xfs/xfs_ioctl.c | 2 +
> fs/xfs/xfs_ioctl32.c | 2 +
> fs/xfs/xfs_iops.c | 2 +
> fs/xfs/xfs_xattr.c | 1 +
> 10 files changed, 137 insertions(+), 19 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index b5a5c84..726b75e 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
...
> @@ -1206,12 +1249,29 @@ xfs_attr_node_removename(
> struct xfs_buf *bp;
> int retval, error, forkoff;
> struct xfs_inode *dp = args->dp;
> + int done = 0;
>
> trace_xfs_attr_node_removename(args);
> + state = args->dac.da_state;
> + blk = args->dac.blk;
> +
> + /* State machine switch */
> + switch (args->dac.dela_state) {
> + case XFS_DAS_RM_NODE_BLKS:
> + goto rm_node_blks;
> + case XFS_DAS_RM_INVALIDATE:
> + goto rm_invalidate;
> + case XFS_DAS_RM_SHRINK:
> + goto rm_shrink;
> + default:
> + break;
> + }

I think this function could use at least a couple more prepatory
refactoring patches before we introduce the state machine...

>
> error = xfs_attr_node_hasname(args, &state);
> if (error != -EEXIST)
> goto out;
> + else
> + error = 0;
>
> /*
> * If there is an out-of-line value, de-allocate the blocks.
> @@ -1221,6 +1281,14 @@ xfs_attr_node_removename(
> blk = &state->path.blk[ state->path.active-1 ];
> ASSERT(blk->bp != NULL);
> ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> +
> + /*
> + * Store blk and state in the context incase we need to cycle out the
> + * transaction
> + */
> + args->dac.blk = blk;
> + args->dac.da_state = state;
> +
> if (args->rmtblkno > 0) {
> /*
> * Fill in disk block numbers in the state structure
> @@ -1239,13 +1307,40 @@ xfs_attr_node_removename(
> if (error)
> goto out;
>
> - error = xfs_trans_roll_inode(&args->trans, args->dp);
> - if (error)
> - goto out;
> + args->dac.dela_state = XFS_DAS_RM_INVALIDATE;
> + return -EAGAIN;
> + }

The entire (args->rmtblkno > 0) branch above could be reduced into a
helper function. BTW, does it matter whether the invalidate occurs
before or after this particular transaction roll? It looks to me it just
makes in-core changes. I'm wondering if we could just fold that in as
well and eliminate that state entirely.

> +
> +rm_invalidate:
> + args->dac.dela_state = XFS_DAS_RM_INVALIDATE;
>
> - error = xfs_attr_rmtval_remove(args);
> + if (args->rmtblkno > 0) {
> + error = xfs_attr_rmtval_invalidate(args);
> if (error)
> goto out;
> + }
> +
> +rm_node_blks:
> +
> + args->dac.dela_state = XFS_DAS_RM_NODE_BLKS;
> + if (args->rmtblkno > 0) {
> + /*
> + * Unmap value blocks for this attr. This is similar to
> + * xfs_attr_rmtval_remove, but open coded here to return EAGAIN
> + * for new transactions
> + */
> + while (!done && !error) {
> + error = xfs_bunmapi(args->trans, args->dp,
> + args->rmtblkno, args->rmtblkcnt,
> + XFS_BMAPI_ATTRFORK, 1, &done);
> + if (error)
> + return error;
> +
> + if (!done) {
> + args->dac.dela_state = XFS_DAS_RM_NODE_BLKS;
> + return -EAGAIN;
> + }
> + }
>

The above could use the helper function treatment as well. E.g.,
something like xfs_attr_rmtval_unmap() that has a *done param this
function can check to determine whether to return -EAGAIN or proceed.

> /*
> * Refill the state structure with buffers, the prior calls
> @@ -1271,17 +1366,14 @@ xfs_attr_node_removename(
> error = xfs_da3_join(state);
> if (error)
> goto out;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - goto out;

Hmm.. I think we might want to lift the xfs_defer_finish() call up into
the iter() function rather than just drop it. Otherwise this changes
behavior in that the transaction roll doesn't complete pending deferred
operations.

> - /*
> - * Commit the Btree join operation and start a new trans.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> - goto out;
> +
> + args->dac.dela_state = XFS_DAS_RM_SHRINK;
> + return -EAGAIN;
> }
>
> +rm_shrink:
> + args->dac.dela_state = XFS_DAS_RM_SHRINK;
> +
> /*
> * If the result is small enough, push it all into the inode.
> */
> @@ -1302,9 +1394,6 @@ xfs_attr_node_removename(
> /* bp is gone due to xfs_da_shrink_inode */
> if (error)
> goto out;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - goto out;
> } else
> xfs_trans_brelse(args->trans, bp);
> }

Same deal here (and same fundamental comment for the next patch)..
create a xfs_attr_node_shrink() or some such helper to make functions
that handle state smaller and easier to follow once the state bits are
introduced.

Brian

> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index 3b5dad4..f6ac571 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -152,6 +152,7 @@ int xfs_attr_set_args(struct xfs_da_args *args);
> int xfs_attr_remove(struct xfs_inode *dp, struct xfs_name *name, int flags);
> int xfs_has_attr(struct xfs_da_args *args);
> int xfs_attr_remove_args(struct xfs_da_args *args);
> +int xfs_attr_remove_iter(struct xfs_da_args *args);
> int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
> int flags, struct attrlist_cursor_kern *cursor);
> bool xfs_attr_namecheck(const void *name, size_t length);
> diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h
> index 580fb72..137ec29 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.h
> +++ b/fs/xfs/libxfs/xfs_da_btree.h
> @@ -49,10 +49,26 @@ enum xfs_dacmp {
> XFS_CMP_CASE /* names are same but differ in case */
> };
>
> +enum xfs_delattr_state {
> + XFS_DAS_RM_INVALIDATE = 1, /* We are invalidating blocks */
> + XFS_DAS_RM_SHRINK = 2, /* We are shrinking the tree */
> + XFS_DAS_RM_NODE_BLKS = 3,/* We are removing node blocks */
> +};
> +
> +/*
> + * Context used for keeping track of delayed attribute operations
> + */
> +struct xfs_delattr_context {
> + struct xfs_da_state *da_state;
> + struct xfs_da_state_blk *blk;
> + enum xfs_delattr_state dela_state;
> +};
> +
> /*
> * Structure to ease passing around component names.
> */
> typedef struct xfs_da_args {
> + struct xfs_delattr_context dac;/* context used for delay attr ops */
> struct xfs_da_geometry *geo; /* da block geometry */
> struct xfs_name name; /* name, length and argument flags*/
> uint8_t filetype; /* filetype of inode for directories */
> diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
> index 1887605..9a649d1 100644
> --- a/fs/xfs/scrub/common.c
> +++ b/fs/xfs/scrub/common.c
> @@ -24,6 +24,8 @@
> #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/scrub.h"
> diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
> index 7b0e5b7..573e47e 100644
> --- a/fs/xfs/xfs_acl.c
> +++ b/fs/xfs/xfs_acl.c
> @@ -10,6 +10,8 @@
> #include "xfs_trans_resv.h"
> #include "xfs_mount.h"
> #include "xfs_inode.h"
> +#include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_trace.h"
> #include "xfs_error.h"
> diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
> index d37743b..881b9a4 100644
> --- a/fs/xfs/xfs_attr_list.c
> +++ b/fs/xfs/xfs_attr_list.c
> @@ -12,6 +12,7 @@
> #include "xfs_trans_resv.h"
> #include "xfs_mount.h"
> #include "xfs_da_format.h"
> +#include "xfs_da_btree.h"
> #include "xfs_inode.h"
> #include "xfs_trans.h"
> #include "xfs_bmap.h"
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 4fc8698..a31753f 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -15,6 +15,8 @@
> #include "xfs_iwalk.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 c4c4f09..4b693e3 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -17,6 +17,8 @@
> #include "xfs_itable.h"
> #include "xfs_fsops.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 e85bbf5..a2d299f 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -13,6 +13,8 @@
> #include "xfs_inode.h"
> #include "xfs_acl.h"
> #include "xfs_quota.h"
> +#include "xfs_da_format.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 5623682..8bdb972 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -10,6 +10,7 @@
> #include "xfs_log_format.h"
> #include "xfs_da_format.h"
> #include "xfs_inode.h"
> +#include "xfs_da_btree.h"
> #include "xfs_attr.h"
> #include "xfs_acl.h"
>
> --
> 2.7.4
>