On Thu, Jun 25, 2020 at 04:30:16PM -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. A new XFS_DAC_DEFER_FINISH flag is used to finish the
> transaction where ever the existing code used to.
>
> Calls to xfs_attr_rmtval_remove are replaced with the delay ready
> version __xfs_attr_rmtval_remove. We will rename
> __xfs_attr_rmtval_remove back to xfs_attr_rmtval_remove when we are
> done.
>
> xfs_attr_rmtval_remove itself is still in use by the set routines (used
> during a rename). For reasons of perserving existing function, we
> modify xfs_attr_rmtval_remove to call xfs_defer_finish when the flag is
> set. Similar to how xfs_attr_remove_args does here. Once we transition
> the set routines to be delay ready, xfs_attr_rmtval_remove is no longer
> used and will be removed.
>
> 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. See xfs_attr.h for a more
> detailed diagram of the states.
>
> Signed-off-by: Allison Collins <allison.henderson@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_attr.c | 155 ++++++++++++++++++++++++++++++----------
> fs/xfs/libxfs/xfs_attr.h | 73 +++++++++++++++++++
> fs/xfs/libxfs/xfs_attr_leaf.c | 2 +-
> fs/xfs/libxfs/xfs_attr_remote.c | 40 +++++------
> fs/xfs/libxfs/xfs_attr_remote.h | 2 +-
> fs/xfs/xfs_attr_inactive.c | 2 +-
> 6 files changed, 208 insertions(+), 66 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 4b78c86..5c460f4 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -53,7 +53,7 @@ STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
> */
> STATIC int xfs_attr_node_get(xfs_da_args_t *args);
> STATIC int xfs_attr_node_addname(xfs_da_args_t *args);
> -STATIC int xfs_attr_node_removename(xfs_da_args_t *args);
> +STATIC int xfs_attr_node_removename(struct xfs_delattr_context *dac);
> STATIC int xfs_attr_node_hasname(xfs_da_args_t *args,
> struct xfs_da_state **state);
> STATIC int xfs_attr_fillstate(xfs_da_state_t *state);
> @@ -264,6 +264,32 @@ xfs_attr_set_shortform(
> }
>
> /*
> + * Checks to see if a delayed attribute transaction should be rolled. If so,
> + * also checks for a defer finish. Transaction is finished and rolled as
> + * needed, and returns true of false if the delayed operation should continue.
> + */
> +bool
> +xfs_attr_roll_again(
The function name suggests this is more of a status checking function
than one that does actual work. I'd suggest something more like
xfs_attr_trans_roll() based on the implementation.
> + struct xfs_delattr_context *dac,
> + int *error)
> +{
> + struct xfs_da_args *args = dac->da_args;
> +
> + if (*error != -EAGAIN)
> + return false;
> +
> + if (dac->flags & XFS_DAC_DEFER_FINISH) {
> + dac->flags &= ~XFS_DAC_DEFER_FINISH;
> + *error = xfs_defer_finish(&args->trans);
> + if (*error)
> + return false;
> + }
> +
I also find the semantics of this function a little confusing. How would
a caller distinguish between error == -EAGAIN as passed in from the
caller vs. error being set by one of the transaction processing calls?
> + *error = xfs_trans_roll_inode(&args->trans, args->dp);
> + return *error == 0;
> +}
> +
> +/*
> * Set the attribute specified in @args.
> */
> int
> @@ -364,23 +390,47 @@ xfs_has_attr(
> */
> int
> xfs_attr_remove_args(
> - struct xfs_da_args *args)
> + struct xfs_da_args *args)
> {
> - struct xfs_inode *dp = args->dp;
> - int error;
> + int error = 0;
> + struct xfs_delattr_context dac = {
> + .da_args = args,
> + };
> +
> + do {
> + error = xfs_attr_remove_iter(&dac);
> + } while (xfs_attr_roll_again(&dac, &error));
> +
> + return error;
> +}
> +
> +/*
> + * Remove the attribute specified in @args.
> + *
> + * This function may return -EAGAIN to signal that the transaction needs to be
> + * rolled. Callers should continue calling this function until they receive a
> + * return value other than -EAGAIN.
> + */
> +int
> +xfs_attr_remove_iter(
> + struct xfs_delattr_context *dac)
> +{
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> +
> + if (dac->dela_state == XFS_DAS_RM_SHRINK)
> + goto node;
Thoughts on my comments on this on the previous version?
>
> if (!xfs_inode_hasattr(dp)) {
> - error = -ENOATTR;
> + return -ENOATTR;
> } else if (dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL) {
> ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> - error = xfs_attr_shortform_remove(args);
> + return xfs_attr_shortform_remove(args);
> } else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> - error = xfs_attr_leaf_removename(args);
> - } else {
> - error = xfs_attr_node_removename(args);
> + return xfs_attr_leaf_removename(args);
> }
> -
> - return error;
> +node:
> + return xfs_attr_node_removename(dac);
> }
>
> /*
...
> @@ -1268,17 +1348,14 @@ xfs_attr_node_removename(
> error = xfs_da3_join(state);
> if (error)
> goto out;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - goto out;
> - /*
> - * Commit the Btree join operation and start a new trans.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> - goto out;
> +
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> + dac->dela_state = XFS_DAS_RM_SHRINK;
> + return -EAGAIN;
> }
>
> +das_rm_shrink:
> +
I think I also mentioned the tail of this function might sit better in
the caller..
Brian
> /*
> * If the result is small enough, push it all into the inode.
> */
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index 3e97a93..6c58792 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -74,6 +74,75 @@ struct xfs_attr_list_context {
> };
>
>
> +/*
> + * ========================================================================
> + * Structure used to pass context around among the delayed routines.
> + * ========================================================================
> + */
> +
> +/*
> + * Below is a state machine diagram for attr remove operations. The XFS_DAS_*
> + * states indicate places where the function would return -EAGAIN, and then
> + * immediately resume from after being recalled by the calling function. States
> + * marked as a "subroutine state" indicate that they belong to a subroutine, and
> + * so the calling function needs to pass them back to that subroutine to allow
> + * it to finish where it left off. But they otherwise do not have a role in the
> + * calling function other than just passing through.
> + *
> + * xfs_attr_remove_iter()
> + * XFS_DAS_RM_SHRINK ─┐
> + * (subroutine state) │
> + * └─>xfs_attr_node_removename()
> + * │
> + * v
> + * need to
> + * shrink tree? ─n─┐
> + * │ │
> + * y │
> + * │ │
> + * v │
> + * XFS_DAS_RM_SHRINK │
> + * │ │
> + * v │
> + * done <─────┘
> + *
> + */
> +
> +/*
> + * Enum values for xfs_delattr_context.da_state
> + *
> + * These values are used by delayed attribute operations to keep track of where
> + * they were before they returned -EAGAIN. A return code of -EAGAIN signals the
> + * calling function to roll the transaction, and then recall the subroutine to
> + * finish the operation. The enum is then used by the subroutine to jump back
> + * to where it was and resume executing where it left off.
> + */
> +enum xfs_delattr_state {
> + /* Zero is uninitalized */
> + XFS_DAS_RM_SHRINK = 1, /* We are shrinking the tree */
> +};
> +
> +/*
> + * Defines for xfs_delattr_context.flags
> + */
> +#define XFS_DAC_DEFER_FINISH 0x01 /* finish the transaction */
> +#define XFS_DAC_NODE_RMVNAME_INIT 0x02 /* xfs_attr_node_removename init */
> +
> +/*
> + * Context used for keeping track of delayed attribute operations
> + */
> +struct xfs_delattr_context {
> + struct xfs_da_args *da_args;
> +
> + /* Used in xfs_attr_node_removename to roll through removing blocks */
> + struct xfs_da_state *da_state;
> + struct xfs_da_state_blk *blk;
> +
> + /* Used to keep track of current state of delayed operation */
> + unsigned int flags;
> + enum xfs_delattr_state dela_state;
> +};
> +
> /*========================================================================
> * Function prototypes for the kernel.
> *========================================================================*/
> @@ -91,6 +160,10 @@ int xfs_attr_set(struct xfs_da_args *args);
> int xfs_attr_set_args(struct xfs_da_args *args);
> 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_delattr_context *dac);
> +bool xfs_attr_roll_again(struct xfs_delattr_context *dac, int *error);
> bool xfs_attr_namecheck(const void *name, size_t length);
> +void xfs_delattr_context_init(struct xfs_delattr_context *dac,
> + struct xfs_da_args *args);
>
> #endif /* __XFS_ATTR_H__ */
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 351351c..20521bf 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -19,8 +19,8 @@
> #include "xfs_bmap_btree.h"
> #include "xfs_bmap.h"
> #include "xfs_attr_sf.h"
> -#include "xfs_attr_remote.h"
> #include "xfs_attr.h"
> +#include "xfs_attr_remote.h"
> #include "xfs_attr_leaf.h"
> #include "xfs_error.h"
> #include "xfs_trace.h"
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
> index 85dca51..20e4605 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.c
> +++ b/fs/xfs/libxfs/xfs_attr_remote.c
> @@ -676,12 +676,14 @@ xfs_attr_rmtval_invalidate(
> */
> int
> xfs_attr_rmtval_remove(
> - struct xfs_da_args *args)
> + struct xfs_da_args *args)
> {
> - xfs_dablk_t lblkno;
> - int blkcnt;
> - int error = 0;
> - int retval = 0;
> + xfs_dablk_t lblkno;
> + int blkcnt;
> + int error = 0;
> + struct xfs_delattr_context dac = {
> + .da_args = args,
> + };
>
> trace_xfs_attr_rmtval_remove(args);
>
> @@ -691,19 +693,10 @@ xfs_attr_rmtval_remove(
> lblkno = args->rmtblkno;
> blkcnt = args->rmtblkcnt;
> do {
> - retval = __xfs_attr_rmtval_remove(args);
> - if (retval && retval != EAGAIN)
> - return retval;
> -
> - /*
> - * Close out trans and start the next one in the chain.
> - */
> - error = xfs_trans_roll_inode(&args->trans, args->dp);
> - if (error)
> - return error;
> - } while (retval == -EAGAIN);
> + error = __xfs_attr_rmtval_remove(&dac);
> + } while (xfs_attr_roll_again(&dac, &error));
>
> - return 0;
> + return error;
> }
>
> /*
> @@ -713,9 +706,10 @@ xfs_attr_rmtval_remove(
> */
> int
> __xfs_attr_rmtval_remove(
> - struct xfs_da_args *args)
> + struct xfs_delattr_context *dac)
> {
> - int error, done;
> + struct xfs_da_args *args = dac->da_args;
> + int error, done;
>
> /*
> * Unmap value blocks for this attr.
> @@ -725,12 +719,10 @@ __xfs_attr_rmtval_remove(
> if (error)
> return error;
>
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - return error;
> -
> - if (!done)
> + if (!done) {
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> return -EAGAIN;
> + }
>
> return error;
> }
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.h b/fs/xfs/libxfs/xfs_attr_remote.h
> index 9eee615..002fd30 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.h
> +++ b/fs/xfs/libxfs/xfs_attr_remote.h
> @@ -14,5 +14,5 @@ int xfs_attr_rmtval_remove(struct xfs_da_args *args);
> int xfs_attr_rmtval_stale(struct xfs_inode *ip, struct xfs_bmbt_irec *map,
> xfs_buf_flags_t incore_flags);
> int xfs_attr_rmtval_invalidate(struct xfs_da_args *args);
> -int __xfs_attr_rmtval_remove(struct xfs_da_args *args);
> +int __xfs_attr_rmtval_remove(struct xfs_delattr_context *dac);
> #endif /* __XFS_ATTR_REMOTE_H__ */
> diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c
> index bfad669..aaa7e66 100644
> --- a/fs/xfs/xfs_attr_inactive.c
> +++ b/fs/xfs/xfs_attr_inactive.c
> @@ -15,10 +15,10 @@
> #include "xfs_da_format.h"
> #include "xfs_da_btree.h"
> #include "xfs_inode.h"
> +#include "xfs_attr.h"
> #include "xfs_attr_remote.h"
> #include "xfs_trans.h"
> #include "xfs_bmap.h"
> -#include "xfs_attr.h"
> #include "xfs_attr_leaf.h"
> #include "xfs_quota.h"
> #include "xfs_dir2.h"
> --
> 2.7.4
>
