Re: [PATCH RESEND v18 11/11] xfs: Add delay ready attr set routines

Darrick J. Wong
2021-05-14T01:14:54Z

On Wed, May 12, 2021 at 09:14:08AM -0700, Allison Henderson wrote:
> This patch modifies the attr set 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_set_args has become xfs_attr_set_iter, which uses a
> state machine like switch to keep track of where it was when EAGAIN was
> returned. See xfs_attr.h for a more detailed diagram of the states.
>
> Two new helper functions have been added: xfs_attr_rmtval_find_space and
> xfs_attr_rmtval_set_blk. They provide a subset of logic similar to
> xfs_attr_rmtval_set, but they store the current block in the delay attr
> context to allow the caller to roll the transaction between allocations.
> This helps to simplify and consolidate code used by
> xfs_attr_leaf_addname and xfs_attr_node_addname. xfs_attr_set_args has
> now become a simple loop to refresh the transaction until the operation
> is completed. Lastly, xfs_attr_rmtval_remove is no longer used, and is
> removed.
>
> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>

Heh, I already reviewed this, but I see a few things that could be
cleaned up a bit as a followon...

> Reviewed-by: Brian Foster <bfoster@redhat.com>
> ---
> fs/xfs/libxfs/xfs_attr.c | 450 ++++++++++++++++++++++++----------------
> fs/xfs/libxfs/xfs_attr.h | 272 +++++++++++++++++++++++-
> fs/xfs/libxfs/xfs_attr_remote.c | 100 ++++++---
> fs/xfs/libxfs/xfs_attr_remote.h | 5 +-
> fs/xfs/xfs_trace.h | 1 -
> 5 files changed, 608 insertions(+), 220 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index a91fff6..4096418 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -53,15 +53,16 @@ STATIC int xfs_attr_leaf_try_add(struct xfs_da_args *args, struct xfs_buf *bp);
> */
> STATIC int xfs_attr_node_get(xfs_da_args_t *args);
> STATIC void xfs_attr_restore_rmt_blk(struct xfs_da_args *args);
> -STATIC int xfs_attr_node_addname(struct xfs_da_args *args,
> - struct xfs_da_state *state);
> -STATIC int xfs_attr_node_addname_find_attr(struct xfs_da_args *args,
> - struct xfs_da_state **state);
> -STATIC int xfs_attr_node_addname_clear_incomplete(struct xfs_da_args *args);
> +STATIC int xfs_attr_node_addname(struct xfs_delattr_context *dac);
> +STATIC int xfs_attr_node_addname_find_attr(struct xfs_delattr_context *dac);
> +STATIC int xfs_attr_node_addname_clear_incomplete(
> + 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);
> STATIC int xfs_attr_refillstate(xfs_da_state_t *state);
> +STATIC int xfs_attr_set_iter(struct xfs_delattr_context *dac,
> + struct xfs_buf **leaf_bp);
>
> int
> xfs_inode_hasattr(
> @@ -244,7 +245,7 @@ xfs_attr_is_shortform(
> * Checks to see if a delayed attribute transaction should be rolled. If so,
> * transaction is finished or rolled as needed.
> */
> -int
> +STATIC int
> xfs_attr_trans_roll(
> struct xfs_delattr_context *dac)
> {
> @@ -265,29 +266,58 @@ xfs_attr_trans_roll(
> return error;
> }
>
> +/*
> + * Set the attribute specified in @args.
> + */
> +int
> +xfs_attr_set_args(
> + struct xfs_da_args *args)
> +{
> + struct xfs_buf *leaf_bp = NULL;
> + int error = 0;
> + struct xfs_delattr_context dac = {
> + .da_args = args,
> + };
> +
> + do {
> + error = xfs_attr_set_iter(&dac, &leaf_bp);
> + if (error != -EAGAIN)
> + break;
> +
> + error = xfs_attr_trans_roll(&dac);
> + if (error) {
> + if (leaf_bp)
> + xfs_trans_brelse(args->trans, leaf_bp);
> + return error;
> + }
> + } while (true);
> +
> + return error;
> +}
> +
> STATIC int
> xfs_attr_set_fmt(
> - struct xfs_da_args *args)
> + struct xfs_delattr_context *dac,
> + struct xfs_buf **leaf_bp)
> {
> - struct xfs_buf *leaf_bp = NULL;
> - struct xfs_inode *dp = args->dp;
> - int error2, error = 0;
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> + int error = 0;
>
> /*
> * Try to add the attr to the attribute list in the inode.
> */
> error = xfs_attr_try_sf_addname(dp, args);
> - if (error != -ENOSPC) {
> - error2 = xfs_trans_commit(args->trans);
> - args->trans = NULL;
> - return error ? error : error2;
> - }
> +
> + /* Should only be 0, -EEXIST or -ENOSPC */
> + if (error != -ENOSPC)
> + return error;
>
> /*
> * It won't fit in the shortform, transform to a leaf block.
> * GROT: another possible req'mt for a double-split btree op.
> */
> - error = xfs_attr_shortform_to_leaf(args, &leaf_bp);
> + error = xfs_attr_shortform_to_leaf(args, leaf_bp);
> if (error)
> return error;
>
> @@ -296,102 +326,130 @@ xfs_attr_set_fmt(
> * concurrent AIL push cannot grab the half-baked leaf buffer
> * and run into problems with the write verifier.
> */
> - xfs_trans_bhold(args->trans, leaf_bp);
> - error = xfs_defer_finish(&args->trans);
> - xfs_trans_bhold_release(args->trans, leaf_bp);
> - if (error) {
> - xfs_trans_brelse(args->trans, leaf_bp);
> - return error;
> - }
> + xfs_trans_bhold(args->trans, *leaf_bp);
>
> + /*
> + * We're still in XFS_DAS_UNINIT state here. We've converted
> + * the attr fork to leaf format and will restart with the leaf
> + * add.
> + */
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> return -EAGAIN;
> }
>
> /*
> * Set the attribute specified in @args.
> + * This routine is meant to function as a delayed operation, and may return
> + * -EAGAIN when the transaction needs to be rolled. Calling functions will need
> + * to handle this, and recall the function until a successful error code is
> + * returned.
> */
> int
> -xfs_attr_set_args(
> - struct xfs_da_args *args)
> +xfs_attr_set_iter(
> + struct xfs_delattr_context *dac,
> + struct xfs_buf **leaf_bp)
> {
> - struct xfs_inode *dp = args->dp;
> - struct xfs_buf *bp = NULL;
> - struct xfs_da_state *state = NULL;
> - int forkoff, error = 0;
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> + struct xfs_buf *bp = NULL;
> + int forkoff, error = 0;
>
> - /*
> - * If the attribute list is already in leaf format, jump straight to
> - * leaf handling. Otherwise, try to add the attribute to the shortform
> - * list; if there's no room then convert the list to leaf format and try
> - * again.
> - */
> - if (xfs_attr_is_shortform(dp)) {
> - error = xfs_attr_set_fmt(args);
> - if (error != -EAGAIN)
> - return error;
> - }
> + /* State machine switch */
> + switch (dac->dela_state) {
> + case XFS_DAS_UNINIT:
> + /*
> + * If the fork is shortform, attempt to add the attr. If there
> + * is no space, this converts to leaf format and returns
> + * -EAGAIN with the leaf buffer held across the roll. The caller
> + * will deal with a transaction roll error, but otherwise
> + * release the hold once we return with a clean transaction.
> + */
> + if (xfs_attr_is_shortform(dp))
> + return xfs_attr_set_fmt(dac, leaf_bp);

More post-series renaming nits:

These probably ought to be renamed xfs_attr_sf_addname or something to go
with the _removename functions...

> + if (*leaf_bp != NULL) {
> + xfs_trans_bhold_release(args->trans, *leaf_bp);
> + *leaf_bp = NULL;
> + }
>
> - if (xfs_attr_is_leaf(dp)) {
> - error = xfs_attr_leaf_try_add(args, bp);
> - if (error == -ENOSPC) {
> - /*
> - * Promote the attribute list to the Btree format.
> - */
> - error = xfs_attr3_leaf_to_node(args);
> - if (error)
> + if (xfs_attr_is_leaf(dp)) {
> + error = xfs_attr_leaf_try_add(args, *leaf_bp);
> + if (error == -ENOSPC) {
> + error = xfs_attr3_leaf_to_node(args);
> + if (error)
> + return error;
> +
> + /*
> + * Finish any deferred work items and roll the
> + * transaction once more. The goal here is to
> + * call node_addname with the inode and
> + * transaction in the same state (inode locked
> + * and joined, transaction clean) no matter how
> + * we got to this step.
> + *
> + * At this point, we are still in
> + * XFS_DAS_UNINIT, but when we come back, we'll
> + * be a node, so we'll fall down into the node
> + * handling code below
> + */
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> + return -EAGAIN;
> + } else if (error) {
> return error;
> + }
>
> - /*
> - * Finish any deferred work items and roll the transaction once
> - * more. The goal here is to call node_addname with the inode
> - * and transaction in the same state (inode locked and joined,
> - * transaction clean) no matter how we got to this step.
> - */
> - error = xfs_defer_finish(&args->trans);
> + dac->dela_state = XFS_DAS_FOUND_LBLK;

Can you lift just whole if block into a separate xfs_attr_leaf_addname
function? Especially since the state diagram indicates such a function
and would result in this chunk losing two levels of indent?

I know, we got rid of it three patches ago, but at least the replacement
would be shorter than the old version.

> + } else {
> + error = xfs_attr_node_addname_find_attr(dac);
> if (error)
> return error;
>
> - /*
> - * Commit the current trans (including the inode) and
> - * start a new one.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> + error = xfs_attr_node_addname(dac);
> if (error)
> return error;
>
> - goto node;
> - } else if (error) {
> - return error;
> + dac->dela_state = XFS_DAS_FOUND_NBLK;

... and then maybe this chunk can lose one level of indent?

> }
> -
> - /*
> - * Commit the transaction that added the attr name so that
> - * later routines can manage their own transactions.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> - return error;
> -
> + return -EAGAIN;
> + case XFS_DAS_FOUND_LBLK:
> /*
> * If there was an out-of-line value, allocate the blocks we
> * identified for its storage and copy the value. This is done
> * after we create the attribute so that we don't overflow the
> * maximum size of a transaction and/or hit a deadlock.
> */
> - if (args->rmtblkno > 0) {
> - error = xfs_attr_rmtval_set(args);
> +
> + /* Open coded xfs_attr_rmtval_set without trans handling */

xfs_attr_rmtval_set has no callers, is that just sitting around waiting
for the log item patchset coming next?

> + if ((dac->flags & XFS_DAC_LEAF_ADDNAME_INIT) == 0) {
> + dac->flags |= XFS_DAC_LEAF_ADDNAME_INIT;
> + if (args->rmtblkno > 0) {
> + error = xfs_attr_rmtval_find_space(dac);
> + if (error)
> + return error;
> + }
> + }
> +
> + /*
> + * Repeat allocating remote blocks for the attr value until
> + * blkcnt drops to zero.
> + */
> + if (dac->blkcnt > 0) {
> + error = xfs_attr_rmtval_set_blk(dac);
> if (error)
> return error;
> + return -EAGAIN;
> }
>
> + error = xfs_attr_rmtval_set_value(args);
> + if (error)
> + return error;
> +
> + /*
> + * If this is not a rename, clear the incomplete flag and we're
> + * done.
> + */
> if (!(args->op_flags & XFS_DA_OP_RENAME)) {
> - /*
> - * Added a "remote" value, just clear the incomplete
> - *flag.
> - */
> if (args->rmtblkno > 0)
> error = xfs_attr3_leaf_clearflag(args);
> -
> return error;
> }
>
> @@ -404,7 +462,6 @@ xfs_attr_set_args(
> * In a separate transaction, set the incomplete flag on the
> * "old" attr and clear the incomplete flag on the "new" attr.
> */
> -
> error = xfs_attr3_leaf_flipflags(args);
> if (error)
> return error;
> @@ -412,29 +469,37 @@ xfs_attr_set_args(
> * Commit the flag value change and start the next trans in
> * series.
> */
> - error = xfs_trans_roll_inode(&args->trans, args->dp);
> - if (error)
> - return error;
> -
> + dac->dela_state = XFS_DAS_FLIP_LFLAG;
> + return -EAGAIN;
> + case XFS_DAS_FLIP_LFLAG:
> /*
> * Dismantle the "old" attribute/value pair by removing a
> * "remote" value (if it exists).
> */
> xfs_attr_restore_rmt_blk(args);
> + error = xfs_attr_rmtval_invalidate(args);
> + if (error)
> + return error;
>
> + /* fallthrough */
> + case XFS_DAS_RM_LBLK:
> + /* Set state in case xfs_attr_rmtval_remove returns -EAGAIN */
> + dac->dela_state = XFS_DAS_RM_LBLK;
> if (args->rmtblkno) {
> - error = xfs_attr_rmtval_invalidate(args);
> + error = __xfs_attr_rmtval_remove(dac);
> if (error)
> return error;
>
> - error = xfs_attr_rmtval_remove(args);
> - if (error)
> - return error;
> + dac->dela_state = XFS_DAS_RD_LEAF;
> + return -EAGAIN;
> }
>
> + /* fallthrough */
> + case XFS_DAS_RD_LEAF:
> /*
> - * Read in the block containing the "old" attr, then remove the
> - * "old" attr from that block (neat, huh!)
> + * This is the last step for leaf format. Read the block with
> + * the old attr, remove the old attr, check for shortform
> + * conversion and return.
> */
> error = xfs_attr3_leaf_read(args->trans, args->dp, args->blkno,
> &bp);
> @@ -443,97 +508,116 @@ xfs_attr_set_args(
>
> xfs_attr3_leaf_remove(bp, args);
>
> - /*
> - * If the result is small enough, shrink it all into the inode.
> - */
> forkoff = xfs_attr_shortform_allfit(bp, dp);
> if (forkoff)
> error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
> /* bp is gone due to xfs_da_shrink_inode */
>
> return error;
> - }
> -node:
>
> + case XFS_DAS_FOUND_NBLK:
> + /*
> + * Find space for remote blocks and fall into the allocation
> + * state.
> + */
> + if (args->rmtblkno > 0) {
> + error = xfs_attr_rmtval_find_space(dac);
> + if (error)
> + return error;
> + }
>
> - do {
> - error = xfs_attr_node_addname_find_attr(args, &state);
> - if (error)
> - return error;
> - error = xfs_attr_node_addname(args, state);
> - } while (error == -EAGAIN);
> - if (error)
> - return error;
> + /* fallthrough */
> + case XFS_DAS_ALLOC_NODE:
> + /*
> + * If there was an out-of-line value, allocate the blocks we
> + * identified for its storage and copy the value. This is done
> + * after we create the attribute so that we don't overflow the
> + * maximum size of a transaction and/or hit a deadlock.
> + */
> + dac->dela_state = XFS_DAS_ALLOC_NODE;
> + if (args->rmtblkno > 0) {
> + if (dac->blkcnt > 0) {
> + error = xfs_attr_rmtval_set_blk(dac);
> + if (error)
> + return error;
> + return -EAGAIN;
> + }
> +
> + error = xfs_attr_rmtval_set_value(args);
> + if (error)
> + return error;
> + }
>
> - /*
> - * Commit the leaf addition or btree split and start the next
> - * trans in the chain.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> - goto out;
> + /*
> + * If this was not a rename, clear the incomplete flag and we're
> + * done.
> + */
> + if (!(args->op_flags & XFS_DA_OP_RENAME)) {
> + if (args->rmtblkno > 0)
> + error = xfs_attr3_leaf_clearflag(args);
> + goto out;
> + }
>
> - /*
> - * If there was an out-of-line value, allocate the blocks we
> - * identified for its storage and copy the value. This is done
> - * after we create the attribute so that we don't overflow the
> - * maximum size of a transaction and/or hit a deadlock.
> - */
> - if (args->rmtblkno > 0) {
> - error = xfs_attr_rmtval_set(args);
> + /*
> + * If this is an atomic rename operation, we must "flip" the
> + * incomplete flags on the "new" and "old" attribute/value pairs
> + * so that one disappears and one appears atomically. Then we
> + * must remove the "old" attribute/value pair.
> + *
> + * In a separate transaction, set the incomplete flag on the
> + * "old" attr and clear the incomplete flag on the "new" attr.
> + */
> + error = xfs_attr3_leaf_flipflags(args);
> if (error)
> - return error;
> - }
> -
> - if (!(args->op_flags & XFS_DA_OP_RENAME)) {
> + goto out;
> /*
> - * Added a "remote" value, just clear the incomplete flag.
> + * Commit the flag value change and start the next trans in
> + * series
> */
> - if (args->rmtblkno > 0)
> - error = xfs_attr3_leaf_clearflag(args);
> - goto out;
> - }
> -
> - /*
> - * If this is an atomic rename operation, we must "flip" the incomplete
> - * flags on the "new" and "old" attribute/value pairs so that one
> - * disappears and one appears atomically. Then we must remove the "old"
> - * attribute/value pair.
> - *
> - * In a separate transaction, set the incomplete flag on the "old" attr
> - * and clear the incomplete flag on the "new" attr.
> - */
> - error = xfs_attr3_leaf_flipflags(args);
> - if (error)
> - goto out;
> - /*
> - * Commit the flag value change and start the next trans in series
> - */
> - error = xfs_trans_roll_inode(&args->trans, args->dp);
> - if (error)
> - goto out;
> + dac->dela_state = XFS_DAS_FLIP_NFLAG;
> + return -EAGAIN;
>
> - /*
> - * Dismantle the "old" attribute/value pair by removing a "remote" value
> - * (if it exists).
> - */
> - xfs_attr_restore_rmt_blk(args);
> + case XFS_DAS_FLIP_NFLAG:
> + /*
> + * Dismantle the "old" attribute/value pair by removing a
> + * "remote" value (if it exists).
> + */
> + xfs_attr_restore_rmt_blk(args);
>
> - if (args->rmtblkno) {
> error = xfs_attr_rmtval_invalidate(args);
> if (error)
> return error;
>
> - error = xfs_attr_rmtval_remove(args);
> - if (error)
> - return error;
> - }
> + /* fallthrough */
> + case XFS_DAS_RM_NBLK:
> + /* Set state in case xfs_attr_rmtval_remove returns -EAGAIN */
> + dac->dela_state = XFS_DAS_RM_NBLK;
> + if (args->rmtblkno) {
> + error = __xfs_attr_rmtval_remove(dac);
> + if (error)
> + return error;
> +
> + dac->dela_state = XFS_DAS_CLR_FLAG;
> + return -EAGAIN;
> + }
>
> - error = xfs_attr_node_addname_clear_incomplete(args);
> + /* fallthrough */
> + case XFS_DAS_CLR_FLAG:
> + /*
> + * The last state for node format. Look up the old attr and
> + * remove it.
> + */
> + error = xfs_attr_node_addname_clear_incomplete(dac);
> + break;
> + default:
> + ASSERT(dac->dela_state != XFS_DAS_RM_SHRINK);

How would we end up in RM_SHRINK? Isn't that only set in the remove
path?

> + break;
> + }
> out:
> return error;
> }
>
> +
> /*
> * Return EEXIST if attr is found, or ENOATTR if not
> */
> @@ -997,18 +1081,18 @@ xfs_attr_node_hasname(
>
> STATIC int
> xfs_attr_node_addname_find_attr(
> - struct xfs_da_args *args,
> - struct xfs_da_state **state)
> + struct xfs_delattr_context *dac)
> {
> - int retval;
> + struct xfs_da_args *args = dac->da_args;
> + int retval;
>
> /*
> * Search to see if name already exists, and get back a pointer
> * to where it should go.
> */
> - retval = xfs_attr_node_hasname(args, state);
> + retval = xfs_attr_node_hasname(args, &dac->da_state);
> if (retval != -ENOATTR && retval != -EEXIST)
> - goto error;
> + return retval;
>
> if (retval == -ENOATTR && (args->attr_flags & XATTR_REPLACE))
> goto error;
> @@ -1034,8 +1118,8 @@ xfs_attr_node_addname_find_attr(
>
> return 0;
> error:
> - if (*state)
> - xfs_da_state_free(*state);
> + if (dac->da_state)
> + xfs_da_state_free(dac->da_state);
> return retval;
> }
>
> @@ -1048,19 +1132,23 @@ xfs_attr_node_addname_find_attr(
> *
> * "Remote" attribute values confuse the issue and atomic rename operations
> * add a whole extra layer of confusion on top of that.
> + *
> + * This routine is meant to function as a delayed operation, and may return
> + * -EAGAIN when the transaction needs to be rolled. Calling functions will need
> + * to handle this, and recall the function until a successful error code is
> + *returned.
> */
> STATIC int
> xfs_attr_node_addname(
> - struct xfs_da_args *args,
> - struct xfs_da_state *state)
> + struct xfs_delattr_context *dac)
> {
> - struct xfs_da_state_blk *blk;
> - struct xfs_inode *dp;
> - int error;
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_da_state *state = dac->da_state;
> + struct xfs_da_state_blk *blk;
> + int error;
>
> trace_xfs_attr_node_addname(args);
>
> - dp = args->dp;
> blk = &state->path.blk[state->path.active-1];
> ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
>
> @@ -1077,18 +1165,15 @@ xfs_attr_node_addname(
> error = xfs_attr3_leaf_to_node(args);
> if (error)
> goto out;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - goto out;
>
> /*
> - * Commit the node conversion and start the next
> - * trans in the chain.
> + * Now that we have converted the leaf to a node, we can
> + * roll the transaction, and try xfs_attr3_leaf_add
> + * again on re-entry. No need to set dela_state to do
> + * this. dela_state is still unset by this function at
> + * this point.
> */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> - goto out;
> -
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> return -EAGAIN;
> }
>
> @@ -1101,9 +1186,7 @@ xfs_attr_node_addname(
> error = xfs_da3_split(state);
> if (error)
> goto out;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - goto out;
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> } else {
> /*
> * Addition succeeded, update Btree hashvals.
> @@ -1120,8 +1203,9 @@ xfs_attr_node_addname(
>
> STATIC
> int xfs_attr_node_addname_clear_incomplete(
> - struct xfs_da_args *args)
> + struct xfs_delattr_context *dac)
> {
> + struct xfs_da_args *args = dac->da_args;
> struct xfs_da_state *state = NULL;
> struct xfs_da_state_blk *blk;
> int retval = 0;
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index 32736d9..41ad5e8 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -164,6 +164,262 @@ struct xfs_attr_list_context {
> * v
> * done
> *
> + *
> + * Below is a state machine diagram for attr set operations.
> + *
> + * It seems the challenge with understanding this system comes from trying to
> + * absorb the state machine all at once, when really one should only be looking
> + * at it with in the context of a single function. Once a state sensitive
> + * function is called, the idea is that it "takes ownership" of the
> + * state machine. It isn't concerned with the states that may have belonged to
> + * it's calling parent. Only the states relevant to itself or any other
> + * subroutines there in. Once a calling function hands off the state machine to
> + * a subroutine, it needs to respect the simple rule that it doesn't "own" the
> + * state machine anymore, and it's the responsibility of that calling function
> + * to propagate the -EAGAIN back up the call stack. Upon reentry, it is
> + * committed to re-calling that subroutine until it returns something other than
> + * -EAGAIN. Once that subroutine signals completion (by returning anything other
> + * than -EAGAIN), the calling function can resume using the state machine.
> + *
> + * xfs_attr_set_iter()
> + * │
> + * v
> + * ┌─y─ has an attr fork?
> + * │ |
> + * │ n
> + * │ |
> + * │ V
> + * │ add a fork
> + * │ │
> + * └──────────┤
> + * │
> + * V
> + * ┌─y─ is shortform?
> + * │ │
> + * │ V
> + * │ xfs_attr_set_fmt
> + * │ |
> + * │ V
> + * │ xfs_attr_try_sf_addname
> + * │ │
> + * │ V
> + * │ had enough ──y──> done
> + * │ space?
> + * n │

About ^^^ this line crawling down the left side of the flowchart:

How do we go from "y" -> "n" ? Is that a clerical error?

> + * │ n
> + * │ │
> + * │ V
> + * │ transform to leaf
> + * │ │
> + * │ V
> + * │ hold the leaf buffer
> + * │ │
> + * │ V
> + * │ return -EAGAIN
> + * │ Re-enter in
> + * │ leaf form
> + * │
> + * └─> release leaf buffer
> + * if needed
> + * │
> + * V
> + * ┌───n── fork has
> + * │ only 1 blk?
> + * │ │
> + * │ y
> + * │ │
> + * │ v
> + * │ xfs_attr_leaf_try_add()
> + * │ │
> + * │ v
> + * │ had enough ──────────────y─────────────┐
> + * │ space? │
> + * │ │ │
> + * │ n │
> + * │ │ │
> + * │ v │
> + * │ return -EAGAIN │
> + * │ re-enter in │
> + * │ node form │
> + * │ │ │
> + * └──────────┤ │
> + * │ │
> + * V │
> + * xfs_attr_node_addname_find_attr │
> + * determines if this │
> + * is create or rename │
> + * find space to store attr │
> + * │ │
> + * v │
> + * xfs_attr_node_addname │
> + * │ │
> + * v │
> + * fits in a node leaf? ────n─────┐ │
> + * │ ^ v │
> + * │ │ single leaf node? │
> + * │ │ │ │ │
> + * y │ y n │
> + * │ │ │ │ │
> + * v │ v v │
> + * update │ grow the leaf split if │
> + * hashvals └── return -EAGAIN needed │
> + * │ retry leaf add │ │
> + * │ on reentry │ │
> + * ├────────────────────────────┘ │
> + * │ │
> + * v │
> + * need to alloc │
> + * ┌─y── or flip flag? │
> + * │ │ │
> + * │ n │
> + * │ │ │
> + * │ v │
> + * │ done │
> + * │ │
> + * │ │
> + * │ XFS_DAS_FOUND_LBLK <────────────────┘
> + * │ │
> + * │ V
> + * │ xfs_attr_leaf_addname()
> + * │ │
> + * │ v
> + * │ ┌──first time through?
> + * │ │ │
> + * │ │ y
> + * │ │ │
> + * │ n v
> + * │ │ if we have rmt blks
> + * │ │ find space for them
> + * │ │ │
> + * │ └──────────┤
> + * │ │
> + * │ v
> + * │ still have
> + * │ ┌─n─ blks to alloc? <──┐
> + * │ │ │ │
> + * │ │ y │
> + * │ │ │ │
> + * │ │ v │
> + * │ │ alloc one blk │
> + * │ │ return -EAGAIN ──┘
> + * │ │ re-enter with one
> + * │ │ less blk to alloc
> + * │ │
> + * │ │
> + * │ └───> set the rmt
> + * │ value
> + * │ │
> + * │ v
> + * │ was this
> + * │ a rename? ──n─┐
> + * │ │ │
> + * │ y │
> + * │ │ │
> + * │ v │
> + * │ flip incomplete │
> + * │ flag │
> + * │ │ │
> + * │ v │
> + * │ XFS_DAS_FLIP_LFLAG │
> + * │ │ │
> + * │ v │
> + * │ need to remove │
> + * │ old bks? ──n──┤
> + * │ │ │
> + * │ y │
> + * │ │ │
> + * │ V │
> + * │ remove │
> + * │ ┌───> old blks │
> + * │ │ │ │
> + * │ XFS_DAS_RM_LBLK │ │
> + * │ ^ │ │
> + * │ │ v │
> + * │ └──y── more to │
> + * │ remove? │
> + * │ │ │
> + * │ n │
> + * │ │ │
> + * │ v │
> + * │ XFS_DAS_RD_LEAF │
> + * │ │ │
> + * │ v │
> + * │ remove leaf │
> + * │ │ │
> + * │ v │
> + * │ shrink to sf │
> + * │ if needed │
> + * │ │ │
> + * │ v │
> + * │ done <──────┘
> + * │
> + * └──────> XFS_DAS_FOUND_NBLK
> + * │
> + * v
> + * ┌─────n── need to
> + * │ alloc blks?
> + * │ │
> + * │ y
> + * │ │
> + * │ v
> + * │ find space
> + * │ │
> + * │ v
> + * │ ┌─>XFS_DAS_ALLOC_NODE
> + * │ │ │
> + * │ │ v
> + * │ │ alloc blk
> + * │ │ │
> + * │ │ v
> + * │ └──y── need to alloc
> + * │ more blocks?
> + * │ │
> + * │ n
> + * │ │
> + * │ v
> + * │ set the rmt value
> + * │ │
> + * │ v
> + * │ was this
> + * └────────> a rename? ──n─┐
> + * │ │
> + * y │
> + * │ │
> + * v │
> + * flip incomplete │
> + * flag │
> + * │ │
> + * v │
> + * XFS_DAS_FLIP_NFLAG │
> + * │ │
> + * v │
> + * need to │
> + * remove blks? ─n──┤
> + * │ │
> + * y │
> + * │ │
> + * v │
> + * remove │
> + * ┌────────> old blks │
> + * │ │ │
> + * XFS_DAS_RM_NBLK │ │
> + * ^ │ │
> + * │ v │
> + * └──────y── more to │
> + * remove │
> + * │ │
> + * n │
> + * │ │
> + * v │
> + * XFS_DAS_CLR_FLAG │
> + * │ │
> + * v │
> + * clear flags │
> + * │ │
> + * ├──────────┘
> + * │
> + * v
> + * done
> */
>
> /*
> @@ -180,12 +436,22 @@ enum xfs_delattr_state {
> XFS_DAS_RMTBLK, /* Removing remote blks */
> XFS_DAS_RM_NAME, /* Remove attr name */
> XFS_DAS_RM_SHRINK, /* We are shrinking the tree */
> + XFS_DAS_FOUND_LBLK, /* We found leaf blk for attr */
> + XFS_DAS_FOUND_NBLK, /* We found node blk for attr */
> + XFS_DAS_FLIP_LFLAG, /* Flipped leaf INCOMPLETE attr flag */
> + XFS_DAS_RM_LBLK, /* A rename is removing leaf blocks */
> + XFS_DAS_RD_LEAF, /* Read in the new leaf */
> + XFS_DAS_ALLOC_NODE, /* We are allocating node blocks */
> + XFS_DAS_FLIP_NFLAG, /* Flipped node INCOMPLETE attr flag */
> + XFS_DAS_RM_NBLK, /* A rename is removing node blocks */
> + XFS_DAS_CLR_FLAG, /* Clear incomplete flag */
> };
>
> /*
> * Defines for xfs_delattr_context.flags
> */
> #define XFS_DAC_DEFER_FINISH 0x01 /* finish the transaction */
> +#define XFS_DAC_LEAF_ADDNAME_INIT 0x02 /* xfs_attr_leaf_addname init*/
>
> /*
> * Context used for keeping track of delayed attribute operations
> @@ -193,6 +459,11 @@ enum xfs_delattr_state {
> struct xfs_delattr_context {
> struct xfs_da_args *da_args;
>
> + /* Used in xfs_attr_rmtval_set_blk to roll through allocating blocks */
> + struct xfs_bmbt_irec map;
> + xfs_dablk_t lblkno;
> + int blkcnt;
> +
> /* Used in xfs_attr_node_removename to roll through removing blocks */
> struct xfs_da_state *da_state;
>
> @@ -220,7 +491,6 @@ 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);
> -int xfs_attr_trans_roll(struct xfs_delattr_context *dac);
> 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);
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
> index 2f3c4cc..fc71f10 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.c
> +++ b/fs/xfs/libxfs/xfs_attr_remote.c
> @@ -439,9 +439,9 @@ xfs_attr_rmtval_get(
>
> /*
> * Find a "hole" in the attribute address space large enough for us to drop the
> - * new attribute's value into
> + * new attributes value into
> */
> -STATIC int
> +int
> xfs_attr_rmt_find_hole(
> struct xfs_da_args *args)
> {
> @@ -468,7 +468,7 @@ xfs_attr_rmt_find_hole(
> return 0;
> }
>
> -STATIC int
> +int
> xfs_attr_rmtval_set_value(
> struct xfs_da_args *args)
> {
> @@ -628,6 +628,69 @@ xfs_attr_rmtval_set(
> }
>
> /*
> + * Find a hole for the attr and store it in the delayed attr context. This
> + * initializes the context to roll through allocating an attr extent for a
> + * delayed attr operation
> + */
> +int
> +xfs_attr_rmtval_find_space(
> + struct xfs_delattr_context *dac)
> +{
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_bmbt_irec *map = &dac->map;
> + int error;
> +
> + dac->lblkno = 0;
> + dac->blkcnt = 0;
> + args->rmtblkcnt = 0;
> + args->rmtblkno = 0;
> + memset(map, 0, sizeof(struct xfs_bmbt_irec));
> +
> + error = xfs_attr_rmt_find_hole(args);
> + if (error)
> + return error;
> +
> + dac->blkcnt = args->rmtblkcnt;
> + dac->lblkno = args->rmtblkno;
> +
> + return 0;
> +}
> +
> +/*
> + * Write one block of the value associated with an attribute into the
> + * out-of-line buffer that we have defined for it. This is similar to a subset
> + * of xfs_attr_rmtval_set, but records the current block to the delayed attr
> + * context, and leaves transaction handling to the caller.
> + */
> +int
> +xfs_attr_rmtval_set_blk(
> + struct xfs_delattr_context *dac)
> +{
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> + struct xfs_bmbt_irec *map = &dac->map;
> + int nmap;
> + int error;
> +
> + nmap = 1;
> + error = xfs_bmapi_write(args->trans, dp, (xfs_fileoff_t)dac->lblkno,
> + dac->blkcnt, XFS_BMAPI_ATTRFORK, args->total,
> + map, &nmap);

Nit: indent two tabs for the second and third lines.

--D

> + if (error)
> + return error;
> +
> + ASSERT(nmap == 1);
> + ASSERT((map->br_startblock != DELAYSTARTBLOCK) &&
> + (map->br_startblock != HOLESTARTBLOCK));
> +
> + /* roll attribute extent map forwards */
> + dac->lblkno += map->br_blockcount;
> + dac->blkcnt -= map->br_blockcount;
> +
> + return 0;
> +}
> +
> +/*
> * Remove the value associated with an attribute by deleting the
> * out-of-line buffer that it is stored on.
> */
> @@ -669,37 +732,6 @@ xfs_attr_rmtval_invalidate(
> }
>
> /*
> - * Remove the value associated with an attribute by deleting the
> - * out-of-line buffer that it is stored on.
> - */
> -int
> -xfs_attr_rmtval_remove(
> - struct xfs_da_args *args)
> -{
> - int error;
> - struct xfs_delattr_context dac = {
> - .da_args = args,
> - };
> -
> - trace_xfs_attr_rmtval_remove(args);
> -
> - /*
> - * Keep de-allocating extents until the remote-value region is gone.
> - */
> - do {
> - error = __xfs_attr_rmtval_remove(&dac);
> - if (error && error != -EAGAIN)
> - break;
> -
> - error = xfs_attr_trans_roll(&dac);
> - if (error)
> - return error;
> - } while (true);
> -
> - return error;
> -}
> -
> -/*
> * Remove the value associated with an attribute by deleting the out-of-line
> * buffer that it is stored on. Returns -EAGAIN for the caller to refresh the
> * transaction and re-call the function
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.h b/fs/xfs/libxfs/xfs_attr_remote.h
> index 002fd30..8ad68d5 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.h
> +++ b/fs/xfs/libxfs/xfs_attr_remote.h
> @@ -10,9 +10,12 @@ int xfs_attr3_rmt_blocks(struct xfs_mount *mp, int attrlen);
>
> int xfs_attr_rmtval_get(struct xfs_da_args *args);
> int xfs_attr_rmtval_set(struct xfs_da_args *args);
> -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_delattr_context *dac);
> +int xfs_attr_rmt_find_hole(struct xfs_da_args *args);
> +int xfs_attr_rmtval_set_value(struct xfs_da_args *args);
> +int xfs_attr_rmtval_set_blk(struct xfs_delattr_context *dac);
> +int xfs_attr_rmtval_find_space(struct xfs_delattr_context *dac);
> #endif /* __XFS_ATTR_REMOTE_H__ */
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 3c1c830..96f93a7 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -1943,7 +1943,6 @@ DEFINE_ATTR_EVENT(xfs_attr_refillstate);
>
> DEFINE_ATTR_EVENT(xfs_attr_rmtval_get);
> DEFINE_ATTR_EVENT(xfs_attr_rmtval_set);
> -DEFINE_ATTR_EVENT(xfs_attr_rmtval_remove);
>
> #define DEFINE_DA_EVENT(name) \
> DEFINE_EVENT(xfs_da_class, name, \
> --
> 2.7.4
>