On Fri, Apr 02, 2021 at 02:01:20AM -0700, Allison Henderson wrote:
>
>
> On 4/1/21 9:57 AM, Brian Foster wrote:
> > On Thu, Mar 25, 2021 at 05:33:08PM -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@xxxxxxxxxx>
> > > Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> > > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > > ---
> > > fs/xfs/libxfs/xfs_attr.c | 446 ++++++++++++++++++++++++----------------
> > > fs/xfs/libxfs/xfs_attr.h | 241 +++++++++++++++++++++-
> > > 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, 582 insertions(+), 211 deletions(-)
> > >
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index 4a73691..6a86b62 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > ...
> > > @@ -246,29 +247,55 @@ 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)
> > > + 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;
> >
> > Ok, so it looks like the commit that goes away here is replaced by one
> > up the call stack.
> >
> > > /*
> > > * 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;
> > > @@ -277,95 +304,139 @@ 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);
> >
> > What about the xfs_trans_brelse() in the error case that seems to
> > disappear?
> Hmm, maybe we could add some handler in xfs_attr_set_args such that if the
> roll fails, we release the leaf_bp if it is not null?
I suspect we need it somewhere. I don't recall the details of this code
off the top of my head, but I remember it being tricky so we should
probably work to preserve current logic unless there's a clear reason to
do otherwise.
> >
> > > - 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;
> > > + struct xfs_da_state *state = 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 (xfs_attr_is_shortform(dp))
> > > + return xfs_attr_set_fmt(dac, leaf_bp);
> > > - if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> > > - 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);
> > > + /*
> > > + * After a shortform to leaf conversion, we need to hold the
> > > + * leaf and cycle out the transaction. When we get back,
> > > + * we need to release the leaf to release the hold on the leaf
> > > + * buffer.
> > > + */
> > > + if (*leaf_bp != NULL) {
> > > + xfs_trans_bhold_release(args->trans, *leaf_bp);
> > > + *leaf_bp = NULL;
> > > + }
> > > +
> > > + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> > > + error = xfs_attr_leaf_try_add(args, *leaf_bp);
> > > + if (error == -ENOSPC) {
> > > + /*
> > > + * Promote the attribute list to the Btree
> > > + * format.
> > > + */
> > > + 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)
> >
> > Nit: } else if (error)
> >
> Sure, will fix
>
> > > + return error;
> > > + }
> > > + else {
> >
> > Nit: } else {
> will fix
>
> >
> > > + error = xfs_attr_node_addname_find_attr(dac);
> > > 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);
> > > + error = xfs_attr_node_addname(dac);
> > > if (error)
> > > return error;
> >
> > Ok, so these couple of node calls get peeled out of the loop that
> > existed prior to this patch and xfs_attr_node_addname() returns -EAGAIN
> > to trigger reentry, if necessary.
> Right, that is the idea
>
> >
> > > /*
> > > - * Commit the current trans (including the inode) and
> > > - * start a new one.
> > > + * If addname was successful, and we dont need to alloc
> > > + * anymore blks, we're done.
> > > */
> > > - error = xfs_trans_roll_inode(&args->trans, dp);
> > > - if (error)
> > > + if (!args->rmtblkno && !args->rmtblkno2)
> > > return error;
> >
> > Is this check new? What about clearing flags and whatnot?
> gosh, I remember putting this in, and now I'm struggling to remember the why
> that lead to it. It's needed later in the set, but at this point its sort
> of an optimization. In the xfs_attr_leaf_try_add, in the case of a rename,
> the blocks are saved for later processing. If no blocks were saved, there's
> nothing to flip, so the idea is we can stop here. The extra go around isnt a
> big deal at this point, but it's a problem in delayed attrs, because you end
> up with an extra empty log entry. in the extended set, we fail an assertion
> with out it:
> Assertion failed: !list_empty(&cil->xc_cil), file: fs/xfs/xfs_log_cil.c,
> line: 907
>
> On my set up, we seem to get away without it at this point in the set, but
> it does have to go in eventually. I think I must have worked through this
> bug at one time, and then placed the fix in this patch, as it seems to be a
> requirement for becoming "delay ready"
>
Hmm, that seems like an odd failure to associate with this code. I guess
it's hard to grok because the context (i.e. delayed attrs) comes a bit
later. If possible, it might be wise to defer this hunk until where it's
necessary so the context/purpose is more clear on review (it also might
be helpful to explain the purpose in a bit more detail in the comment).
>
>
> >
> > > - goto node;
> > > - }
> > > - else if (error) {
> > > - return error;
> > > + dac->dela_state = XFS_DAS_FOUND_NBLK;
> > > + return -EAGAIN;
> > > }
> > > - /*
> > > - * 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;
> > > + dac->dela_state = XFS_DAS_FOUND_LBLK;
> > > + return -EAGAIN;
> >
> > Is there a reason the node branch sets the state in the branch but the
> > leaf branch falls out to here? I.e., could we not be consistent and have
> >
> > if (one_block()) {
> > ...
> > dac->dela_state = XFS_DAS_FOUND_LBLK;
> > } else {
> > ...
> > dac->dela_state = XFS_DAS_FOUND_NBLK;
> > }
> >
> > return -EAGAIN;
> It's just sort of left over from its originally linear code flow that just
> sort of fell through in the the leaf logic. I think what you are proposing
> is logically analogous tho. Does your example mean to add an extra if/else
> at the end here? Or to tuck the return up into the the existing if/else?
> Both work, I am fine with either.
>
Yes, the suggestion was intended to be logically equivalent. I think it
improves readability and is slightly less fragile to make the duplicated
code (i.e. return -EAGAIN) common and the state assignment as part of
the associated branch.
Brian
> >
> > > + 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 */
> > > + 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;
> > > + }
> > > + }
> > > +
> > > + /*
> > > + * Roll through the "value", allocating blocks on disk as
> > > + * required.
> > > + */
> > > + 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 (!(args->op_flags & XFS_DA_OP_RENAME)) {
> > > /*
> > > * Added a "remote" value, just clear the incomplete
> > > @@ -394,22 +465,26 @@ 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);
> > > - if (args->rmtblkno) {
> > > - error = xfs_attr_rmtval_invalidate(args);
> > > - if (error)
> > > - return error;
> > > + error = xfs_attr_rmtval_invalidate(args);
> > > + if (error)
> > > + return error;
> > > +
> > > + /* Set state in case xfs_attr_rmtval_remove returns -EAGAIN */
> > > + dac->dela_state = XFS_DAS_RM_LBLK;
> > > - error = xfs_attr_rmtval_remove(args);
> > > + /* fallthrough */
> > > + case XFS_DAS_RM_LBLK:
> > > + if (args->rmtblkno) {
> > > + error = __xfs_attr_rmtval_remove(dac);
> > > if (error)
> > > return error;
> > > }
> >
> > This looks like a similar scenario as before where
> > xfs_attr_rmtval_remove() would have returned with a clean transaction
> > after the final unmap, but here __xfs_attr_rmtval_remove() just returns
> > 0 if done == 1. We probably need to roll one more time out of this
> > branch and land in a subsequent state..?
> I see, ok will add extra -EAGAIN here.
>
>
> >
> > > @@ -434,91 +509,114 @@ xfs_attr_set_args(
> > > /* bp is gone due to xfs_da_shrink_inode */
> > > return error;
> > > - }
> > > -node:
> > > + case XFS_DAS_FOUND_NBLK:
> > > + /*
> > > + * 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) {
> > > + /*
> > > + * Open coded xfs_attr_rmtval_set without trans
> > > + * handling
> > > + */
> > > + 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;
> > > + /*
> > > + * Roll through the "value", allocating blocks on disk
> > > + * as required. Set the state in case of -EAGAIN return
> > > + * code
> > > + */
> > > + dac->dela_state = XFS_DAS_ALLOC_NODE;
> > > + }
> > > - /*
> > > - * 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;
> > > + /* fallthrough */
> > > + case XFS_DAS_ALLOC_NODE:
> > > + if (args->rmtblkno > 0) {
> > > + if (dac->blkcnt > 0) {
> > > + error = xfs_attr_rmtval_set_blk(dac);
> > > + if (error)
> > > + return error;
> > > - /*
> > > - * 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 (error)
> > > - return error;
> > > - }
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + error = xfs_attr_rmtval_set_value(args);
> > > + if (error)
> > > + return error;
> > > + }
> > > +
> > > + 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);
> > > + goto out;
> > > + }
> > > - if (!(args->op_flags & XFS_DA_OP_RENAME)) {
> > > /*
> > > - * Added a "remote" value, just clear the incomplete flag.
> > > + * 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.
> > > */
> > > - 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;
> > > + error = xfs_attr3_leaf_flipflags(args);
> > > + if (error)
> > > + goto out;
> > > + /*
> > > + * Commit the flag value change and start the next trans in
> > > + * series
> > > + */
> > > + 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;
> > > - }
> > > + /* Set state in case xfs_attr_rmtval_remove returns -EAGAIN */
> > > + dac->dela_state = XFS_DAS_RM_NBLK;
> > > +
> > > + /* fallthrough */
> > > + case XFS_DAS_RM_NBLK:
> > > + if (args->rmtblkno) {
> > > + error = __xfs_attr_rmtval_remove(dac);
> > > + if (error)
> > > + return error;
> > > + }
> >
> > Similar thing here with __xfs_attr_rmtval_remove()..?
> Sure, will add one more -EAGAIN
>
> >
> > > +
> > > + error = xfs_attr_node_addname_clear_incomplete(dac);
> > > - error = xfs_attr_node_addname_clear_incomplete(args);
> > > out:
> > > - if (state)
> > > - xfs_da_state_free(state);
> > > - return error;
> > > + if (state)
> > > + xfs_da_state_free(state);
> > > + return error;
> >
> > Can we avoid this out label landing inside the switch statement? That
> > looks like a landmine. Even if we just duplicated an 'done_out' path
> > after the last return in the function, I think that would be preferable.
> Sure, can do, that seems like a simple thing to tack on
>
> >
> > All previous feedback aside, I think this patch now looks much more
> > digestable in general. Most of the state code is isolated to the _iter()
> > function and so it's much easier to follow along and compare against the
> > current code flow. I did still have some thoughts with regard to further
> > cleanups, possibly clearing up some the logic and/or tweaking the states
> > and whatnot, but I think this is at a point where it might be reasonable
> > to make such changes on top of this patch instead of continuing to make
> > significant changes to it. If I get a chance perhaps I'll take a closer
> > look at that once the remaining kinks are worked out..
> >
> > Brian
> Ok, I will get these last bits updated here. I still need to check into the
> issues Darrick is seeing on his set up, but it sounds like we've found an
> arrangement people like. And yes, I think switching to cleanups on top is a
> good next step. Thanks for the reviews!
>
> Allison
>
> >
> > > +
> > > + default:
> > > + ASSERT(dac->dela_state != XFS_DAS_RM_SHRINK);
> > > + break;
> > > + }
> > > + return error;
> > > }
> > > +
> > > /*
> > > * Return EEXIST if attr is found, or ENOATTR if not
> > > */
> > > @@ -984,18 +1082,18 @@ 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;
> > > @@ -1021,8 +1119,8 @@ 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;
> > > }
> > > @@ -1035,20 +1133,24 @@ 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];
> > > + blk = &state->path.blk[ state->path.active-1 ];
> > > ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> > > error = xfs_attr3_leaf_add(blk->bp, state->args);
> > > @@ -1064,18 +1166,15 @@ 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;
> > > }
> > > @@ -1088,9 +1187,7 @@ 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.
> > > @@ -1105,8 +1202,9 @@ 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 92a6a50..4e4233d 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.h
> > > +++ b/fs/xfs/libxfs/xfs_attr.h
> > > @@ -159,6 +159,233 @@ 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 │
> > > + * │ 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 │
> > > + * │ remove │
> > > + * │ ┌───> old name │
> > > + * │ │ │ │
> > > + * │ XFS_DAS_RM_LBLK │ │
> > > + * │ ^ │ │
> > > + * │ │ v │
> > > + * │ └──y── more to │
> > > + * │ remove │
> > > + * │ │ │
> > > + * │ n │
> > > + * │ │ │
> > > + * │ 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 │
> > > + * remove │
> > > + * ┌────────> old name │
> > > + * │ │ │
> > > + * XFS_DAS_RM_NBLK │ │
> > > + * ^ │ │
> > > + * │ v │
> > > + * └──────y── more to │
> > > + * remove │
> > > + * │ │
> > > + * n │
> > > + * │ │
> > > + * v │
> > > + * done <──────┘
> > > + *
> > > */
> > > /*
> > > @@ -174,12 +401,20 @@ enum xfs_delattr_state {
> > > XFS_DAS_UNINIT = 0, /* No state has been set yet */
> > > XFS_DAS_RMTBLK, /* Removing remote blks */
> > > 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_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 */
> > > };
> > > /*
> > > * 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
> > > @@ -187,6 +422,11 @@ 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;
> > > @@ -213,7 +453,6 @@ 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 908521e7..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);
> > > + 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 != -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 e74bbb6..0c16d46 100644
> > > --- a/fs/xfs/xfs_trace.h
> > > +++ b/fs/xfs/xfs_trace.h
> > > @@ -1944,7 +1944,6 @@ 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
> > >
> >
>
