On Fri, Sep 20, 2019 at 12:12:51PM -0700, Allison Collins wrote:
> On 9/20/19 8:28 AM, Brian Foster wrote:
> > On Thu, Sep 05, 2019 at 03:18:32PM -0700, Allison Collins wrote:
> > > This patch adds new delayed attribute routines:
> > >
> > > xfs_attr_set_later
> > > xfs_attr_remove_later
> > > xfs_leaf_addname_later
> > > xfs_node_addname_later
> > > xfs_node_removename_later
> > >
> > > These routines are similar to their existing counter parts,
> > > but they do not roll or commit transactions. They instead
> > > return -EAGAIN to allow the calling function to roll the
> > > transaction and recall the function. This allows the
> > > attribute operations to be logged in multiple smaller
> > > transactions.
> > >
> > > Signed-off-by: Allison Collins <allison.henderson@xxxxxxxxxx>
> > > ---
> > > fs/xfs/libxfs/xfs_attr.c | 591 ++++++++++++++++++++++++++++++++++++++++++++++-
> > > fs/xfs/libxfs/xfs_attr.h | 2 +
> > > 2 files changed, 592 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index 781dd8a..310f5b2 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > ...
> > > @@ -313,6 +316,112 @@ xfs_attr_set_args(
> > > }
> > > /*
> > > + * Set the attribute specified in @args.
> > > + * This routine is meant to function as a delayed operation, and may return
> > > + * -EGAIN 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_later(
> > > + struct xfs_da_args *args,
> > > + struct xfs_buf **leaf_bp)
> > > +{
> > > + struct xfs_inode *dp = args->dp;
> > > + int error = 0;
> > > + int sf_size;
> > > +
> > > + /*
> > > + * New inodes may not have an attribute fork yet. So set the attribute
> > > + * fork appropriately
> > > + */
> > > + if (XFS_IFORK_Q((args->dp)) == 0) {
> > > + sf_size = sizeof(struct xfs_attr_sf_hdr) +
> > > + XFS_ATTR_SF_ENTSIZE_BYNAME(args->name.len, args->valuelen);
> > > + xfs_bmap_set_attrforkoff(args->dp, sf_size, NULL);
> > > + args->dp->i_afp = kmem_zone_zalloc(xfs_ifork_zone, 0);
> > > + args->dp->i_afp->if_flags = XFS_IFEXTENTS;
> > > + }
> > > +
> > > + /*
> > > + * If the attribute list is non-existent or a shortform list,
> > > + * upgrade it to a single-leaf-block attribute list.
> > > + */
> > > + if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
> > > + (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
> > > + dp->i_d.di_anextents == 0)) {
> > > + /*
> > > + * Build initial attribute list (if required).
> > > + */
> > > + if (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS)
> > > + xfs_attr_shortform_create(args);
> > > +
> > > + /*
> > > + * Try to add the attr to the attribute list in the inode.
> > > + */
> > > + error = xfs_attr_try_sf_addname(dp, args);
> > > + 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);
> > > + if (error)
> > > + return error;
> > > +
> > > + /*
> > > + * Prevent the leaf buffer from being unlocked so that a
> > > + * 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);
> > > + return -EAGAIN;
> > > + }
> >
> > I haven't actually reviewed the code in this patch yet, but rather I
> > skipped ahead to try and get an understanding of the design approach and
> > flow of a deferred xattr operation. IIUC, we basically duplicate a bunch
> > of xattr code into these dfops oriented functions but instead of rolling
> > transactions, return -EAGAIN and use the XFS_DC_ state flags to manage
> > reentrancy into the xfs_trans_attr() function.
>
> Yes. If it helps to know a little more background about how it came into
> being...
> Initially I had started out with the code paths merged, and had a boolean
> switch to control the alternate behavior (much like the "roll_trans" boolean
> from the prior sets, if you recall them). In a way, the boolean acted like
> a sort of marker of where things needed to get factored up. The goal being
> to pull the boolean into the higher level routines as much as possible and
> leaving behind all the little helpers which is what you see now in now
> patches 5 - 12.
>
> After I got done with all the refactoring, the parts that still had the
> boolean were a sort of hybrid of the two paths you see now. At one point I
> made a judgment that continuing to factor up the boolean would be more
> complicated than not. I know people disliked the boolean toggle from the
> prior sets. So the *_later routines we have now are a result of the hybrid
> having been gutted of the boolean and split then off into its separate path.
>
>
> >
> > If I'm following that correctly, I'm concerned about a couple things
> > with the general approach. First, I think the complexity is high and
> > maintainability is low/difficult for this kind of reentrant approach.
>
> Yes. And I did very much anticipate a similar response. Thats certainly
> not to imply that I did all this for giggles, but because I think sometimes
> it's easy for designs to sound like good ideas in theory, until people see
> them in practice. And then the design takes a different direction. In a
> way I think the prototypes are a sort of necessary step for the design to
> evolve, even if the prototypes are sort of ugly. :-)
>
Yeah, tbh I suspect that anything we come up with at first is going to
have an ugliness factor due to the simple fact of how the code is
currently implemented. IMO, the right approach is to take the current
code apart as much as possible (without too much regard for aesthetic),
identify/isolate the smallest functional components required to support
both direct rolling and deferred operation rolling, and then from there
think about cleaning up the design for how to fit those pieces back
together. We might be able to do that in one patch series, but I
wouldn't be surprised (or object to) doing it in several.
IOW, I think it would be reasonable to split off the effort of
refactoring the existing xattr code to be "deferred capable" as an
independent series if you didn't want to have to continue rebasing the
follow on deferred xattr bits and wanted to try and get more rapid
development+review cycles of the refactoring, but that's up to you. The
whole idea for the refactoring is to not change existing behavior, so I
don't see why that couldn't be a mergeable component on its own.
> > The state is managed/changed all throughout the call tree and so the
> > risk and complexity of changing one particular bit in the sequence
> > requires subtle consideration to make sure it doesn't cause problems if
> > the function is reentered.
> Yes, it's still very much a state machine in practice. But I think we may
> be stuck with at least some variant of state machine if we still want to
> adhere to the EAGAIN interface which requires the stack to back out. I have
> pondered the idea of introducing a call back to cycle out the transactions
> mid flight so that we dont need to stop and return. This would escape the
> state machine concept, but may require alternate surgery to the calling log
> routines too. So that may just turn into a different type of monster
>
To be clear, I'm pretty much expecting it to continue to be a state
machine. That seems to be the most simple way to break things down, I
think. I'd rather not get into things like callbacks or whatever until
we've broken down the functional components and have a more clear
picture of things.
BTW, I thought one of your previous series' had a start on this in terms
of just defining some quick and dirty states based on an enum or
something and sticking them in a switch statement..? The point I'm
trying to make is that while those kind of simple enumerated low level
states are probably not where we want to leave things at the end, it
might be a reasonable approach to break the existing code into those
states and then try and polish things from there. I definitely think it
would be easier to review from a design perspective...
> For example, I'd prefer to see something like
> > xfs_trans_attr() broken down into smaller granularity functions with
> > higher level state that is managed and readable in one place, if
> > possible. Perhaps we could do that based on attr fork format, but I need
> > to stare at the code and think about this some more (it might be that
> > some degree of reentrancy is inevitable, or we just need to break things
> > down to even smaller states...).
> Yes, and I did go through a phase of trying to simplify the statemachine by
> trying to grab onto anything about the state of the fork that could be used
> instead. But its not always enough particularly in the case of routines
> that are in the middle of allocating or removing blocks. If you see any
> other mechanics that could help out, please call them out.
>
One of the things I'm wondering is if we'll be able to reduce the number
of unique (sub-)states required by reordering some of the existing logic
between the higher level states. For a quick example, the current series
uses the XFS_DC_ALLOC_LEAF state for a one-time operation that's part of
a state that can be reentered over and over. This raises the question to
me of whether that _ALLOC_LEAF thing could eventually just be folded
into the tail of the previous state.
To reiterate, for now I think it would be perfectly reasonable to make
_ALLOC_LEAF its own independent state so the flag management isn't
buried so deep in the xattr code...
>
> >
> > Second, it seems like a lot of this code duplication between deferred
> > and non-deferred operations should be unnecessary, particularly since
> > the only difference between the contexts is how transactions are
> > managed. For example, if you follow the xattr set code path in both
> > contexts, we can see that functions like xfs_attr_set_args() are
> > basically duplicated in the xfs_attr_set_later() deferred variant just
> > so we can change the xfs_defer_finish() call in the former to a return
> > -EAGAIN in the latter.
> Yes, they still carry some similarities. I guess I reasoned that continuing
> to carve things up into smaller and smaller helpers with out a generalized
> purpose (other than de-dup reduction) was starting to look a little weird,
> and maybe leaving things in their appropriate context might have been
> preferred? Folks are welcome to chime in with opinions though.
>
As mentioned above, I think weird is to be expected, at least if we
break things down into an intermediary state. That's just my .02 though.
Maybe others have different ideas..
> >
> > Instead, what I think we should strive for is a common xattr mechanism
> > that consists of the lowest common denominator between the two contexts
> > (or IOW, core infrastructure that can be invoked from either context).
> > For example, on a kernel without deferred xattr support, could we find a
> > way to call the deferred variants directly and just let the
> > context-specific caller do the transaction rolls on -EAGAIN instead of
> > relying on the dfops infrastructure?
> I think I did that somewhere in the older parent pointer sets. At the time,
> we sort of forgot that we cant completely scrap non delayed attrs (because
> we need them for older versions). But then protofiles needed to create
> pptrs with out the delay mechanic, so I opened coded a sort of loop to deal
> with the EAGAIN. In fact, I ended up doing the same sort of loop in patch
> 15 for xfs_attri_recover, which has the same challenge. Maybe we could make
> a sort of general purpose wrapper?
>
> ISTM that should be possible, it
> > just requires further breaking down the existing/non-deferred mechanism
> > into smaller bits that uses the new state management logic and
> > implements -EAGAIN handling for when the lower level code requires a
> > transaction roll. At that point, deferred support should basically just
> > consist of the dfops and log (i.e. intents) code to plug into the associated
> > infrastructure. I think another side effect of that approach is that we
> > shouldn't need these patches that add a bunch of new xattr
> > infrastructure code, but rather we'd just continue refactoring the
> > existing code and eventually implement a new high level function that
> > returns -EAGAIN directly to the dfops code instead of rolling
> > transactions explicitly. Thoughts?
> Ok, I think I understand what you're trying to describe here. Maybe take a
> look at xfs_attri_recover in patch 15, and let me know if that was similar
> to what you were thinking?
>
Yep, pretty much. Outside of the whole xfs_trans_attr() thing, I'd
expect the direct xattr path to have to do something very similar in
terms of invoking the xattr state machine and handling transaction rolls
where the dfops mechanism isn't there to do it for us.
Brian
> Thank you for all the thorough reviewing here, I know it's a lot!
> Allison
>
> >
> > Brian
> >
> > > +
> > > + /*
> > > + * After a shortform to leaf conversion, we need to hold the leaf and
> > > + * cylce out the transaction. When we get back, we need to release
> > > + * the leaf.
> > > + */
> > > + if (*leaf_bp != NULL) {
> > > + xfs_trans_brelse(args->trans, *leaf_bp);
> > > + *leaf_bp = NULL;
> > > + }
> > > +
> > > + /*
> > > + * If we fit in a block, or we are in the middle of adding a leaf name.
> > > + * xfs_attr_da_leaf_addname will set the XFS_DC_ALLOC_LEAF to indicate
> > > + * that it is not done yet, and need to be recalled to finish up from
> > > + * the last EAGAIN it returned
> > > + */
> > > + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK) ||
> > > + args->dc.flags & XFS_DC_ALLOC_LEAF) {
> > > + if (!(args->dc.flags & XFS_DC_FOUND_LBLK)) {
> > > + error = xfs_attr_leaf_try_add(args, *leaf_bp);
> > > + args->dc.flags |= XFS_DC_FOUND_LBLK;
> > > +
> > > + if (error && error != -ENOSPC)
> > > + return error;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + error = xfs_leaf_addname_later(args);
> > > + if (error && error != -ENOSPC)
> > > + return error;
> > > + } else {
> > > + error = xfs_node_addname_later(args);
> > > + }
> > > +
> > > + return error;
> > > +}
> > > +
> > > +
> > > +
> > > +/*
> > > * Return EEXIST if attr is found, or ENOATTR if not
> > > */
> > > int
> > > @@ -362,6 +471,57 @@ xfs_attr_remove_args(
> > > return error;
> > > }
> > > +/*
> > > + * Remove the attribute specified in @args.
> > > + * This routine is meant to function as a delayed operation, and may return
> > > + * -EGAIN 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_remove_later(
> > > + struct xfs_da_args *args)
> > > +{
> > > + struct xfs_inode *dp = args->dp;
> > > + struct xfs_buf *bp;
> > > + int forkoff, error = 0;
> > > +
> > > + if (!xfs_inode_hasattr(dp)) {
> > > + error = -ENOATTR;
> > > + } else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
> > > + ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> > > + error = xfs_attr_shortform_remove(args);
> > > + } else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK) &&
> > > + !(args->dc.flags & XFS_DC_RM_NODE_BLKS)) {
> > > + /*
> > > + * If we fit in a block AND we are not in the middle of
> > > + * removing node blocks, remove the leaf attribute.
> > > + * xfs_attr_da_node_removename will set XFS_DC_RM_NODE_BLKS to
> > > + * signal that it is not done yet, and needs to be recalled to
> > > + * to finish up from the last -EAGAIN
> > > + */
> > > + error = xfs_leaf_has_attr(args, &bp);
> > > + if (error == -ENOATTR) {
> > > + xfs_trans_brelse(args->trans, bp);
> > > + return error;
> > > + }
> > > + error = 0;
> > > +
> > > + xfs_attr3_leaf_remove(bp, args);
> > > +
> > > + /* If the result is small enough, shrink it into the inode.*/
> > > + forkoff = xfs_attr_shortform_allfit(bp, dp);
> > > + if (forkoff)
> > > + error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
> > > + } else {
> > > + error = xfs_node_removename_later(args);
> > > + }
> > > +
> > > + return error;
> > > +}
> > > +
> > > +
> > > +
> > > int
> > > xfs_attr_set(
> > > struct xfs_inode *dp,
> > > @@ -794,6 +954,87 @@ xfs_attr_leaf_addname(struct xfs_da_args *args)
> > > }
> > > /*
> > > + * Add a name to the leaf attribute list structure
> > > + *
> > > + * This leaf block cannot have a "remote" value, we only call this routine
> > > + * if bmap_one_block() says there is only one block (ie: no remote blks).
> > > + *
> > > + * This routine is meant to function as a delayed operation, and may return
> > > + * -EGAIN 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_leaf_addname_later(
> > > + struct xfs_da_args *args)
> > > +{
> > > + int error, nmap;
> > > + struct xfs_inode *dp = args->dp;
> > > + struct xfs_bmbt_irec *map = &args->dc.map;
> > > +
> > > + /*
> > > + * 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) {
> > > + if (!(args->dc.flags & XFS_DC_ALLOC_LEAF)) {
> > > + args->dc.lfileoff = 0;
> > > + args->dc.lblkno = 0;
> > > + args->dc.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;
> > > +
> > > + args->dc.blkcnt = args->rmtblkcnt;
> > > + args->dc.lblkno = args->rmtblkno;
> > > + args->dc.flags |= XFS_DC_ALLOC_LEAF;
> > > + }
> > > +
> > > + /*
> > > + * Roll through the "value", allocating blocks on disk as
> > > + * required.
> > > + */
> > > + while (args->dc.blkcnt > 0) {
> > > + nmap = 1;
> > > + error = xfs_bmapi_write(args->trans, dp,
> > > + (xfs_fileoff_t)args->dc.lblkno,
> > > + args->dc.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 */
> > > + args->dc.lblkno += map->br_blockcount;
> > > + args->dc.blkcnt -= map->br_blockcount;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + error = xfs_attr_rmtval_set_value(args);
> > > + if (error)
> > > + return error;
> > > + }
> > > +
> > > + if (args->rmtblkno > 0) {
> > > + /*
> > > + * Added a "remote" value, just clear the incomplete flag.
> > > + */
> > > + error = xfs_attr3_leaf_clearflag(args);
> > > + }
> > > + args->dc.flags &= ~XFS_DC_ALLOC_LEAF;
> > > + return error;
> > > +}
> > > +
> > > +/*
> > > * Return EEXIST if attr is found, or ENOATTR if not
> > > */
> > > STATIC int
> > > @@ -1291,6 +1532,354 @@ xfs_attr_node_removename(
> > > }
> > > /*
> > > + * Remove a name from a B-tree attribute list.
> > > + *
> > > + * This will involve walking down the Btree, and may involve joining
> > > + * leaf nodes and even joining intermediate nodes up to and including
> > > + * the root node (a special case of an intermediate node).
> > > + *
> > > + * This routine is meant to function as a delayed operation, and may return
> > > + * -EGAIN 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_node_removename_later(
> > > + struct xfs_da_args *args)
> > > +{
> > > + struct xfs_da_state *state = NULL;
> > > + struct xfs_da_state_blk *blk;
> > > + struct xfs_buf *bp;
> > > + int error, forkoff, retval = 0;
> > > + struct xfs_inode *dp = args->dp;
> > > + int done = 0;
> > > +
> > > + trace_xfs_attr_node_removename(args);
> > > +
> > > + if (args->dc.state == NULL) {
> > > + error = xfs_attr_node_hasname(args, &args->dc.state);
> > > + if (error != -EEXIST)
> > > + goto out;
> > > + else
> > > + error = 0;
> > > +
> > > + /*
> > > + * If there is an out-of-line value, de-allocate the blocks.
> > > + * This is done before we remove the attribute so that we don't
> > > + * overflow the maximum size of a transaction and/or hit a
> > > + * deadlock.
> > > + */
> > > + state = args->dc.state;
> > > + args->dc.blk = &state->path.blk[state->path.active - 1];
> > > + ASSERT(args->dc.blk->bp != NULL);
> > > + ASSERT(args->dc.blk->magic == XFS_ATTR_LEAF_MAGIC);
> > > + }
> > > + state = args->dc.state;
> > > + blk = args->dc.blk;
> > > +
> > > + if (args->rmtblkno > 0 && !(args->dc.flags & XFS_DC_RM_LEAF_BLKS)) {
> > > + bool isset;
> > > +
> > > + error = xfs_attr3_leaf_flag_is_set(args, &isset);
> > > + if (error)
> > > + goto out;
> > > + if (!isset) {
> > > + /*
> > > + * Fill in disk block numbers in the state structure
> > > + * so that we can get the buffers back after we commit
> > > + * several transactions in the following calls.
> > > + */
> > > + error = xfs_attr_fillstate(state);
> > > + if (error)
> > > + goto out;
> > > +
> > > + /*
> > > + * Mark the attribute as INCOMPLETE, then bunmapi() the
> > > + * remote value.
> > > + */
> > > + error = xfs_attr3_leaf_setflag(args);
> > > + if (error)
> > > + goto out;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + if (!(args->dc.flags & XFS_DC_RM_NODE_BLKS)) {
> > > + args->dc.flags |= XFS_DC_RM_NODE_BLKS;
> > > + error = xfs_attr_rmtval_invalidate(args);
> > > + if (error)
> > > + goto out;
> > > + }
> > > +
> > > + /*
> > > + * 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)
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + if (error)
> > > + goto out;
> > > +
> > > + /*
> > > + * Refill the state structure with buffers, the prior calls
> > > + * released our buffers.
> > > + */
> > > + error = xfs_attr_refillstate(state);
> > > + if (error)
> > > + goto out;
> > > + }
> > > +
> > > + /*
> > > + * Remove the name and update the hashvals in the tree.
> > > + */
> > > + if (!(args->dc.flags & XFS_DC_RM_LEAF_BLKS)) {
> > > + blk = &state->path.blk[state->path.active - 1];
> > > + ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> > > + retval = xfs_attr3_leaf_remove(blk->bp, args);
> > > + xfs_da3_fixhashpath(state, &state->path);
> > > +
> > > + args->dc.flags |= XFS_DC_RM_LEAF_BLKS;
> > > + }
> > > +
> > > + /*
> > > + * Check to see if the tree needs to be collapsed.
> > > + */
> > > + if (retval && (state->path.active > 1)) {
> > > + args->dc.flags |= XFS_DC_RM_NODE_BLKS;
> > > + error = xfs_da3_join(state);
> > > + if (error)
> > > + goto out;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + /*
> > > + * If the result is small enough, push it all into the inode.
> > > + */
> > > + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> > > + /*
> > > + * Have to get rid of the copy of this dabuf in the state.
> > > + */
> > > + ASSERT(state->path.active == 1);
> > > + ASSERT(state->path.blk[0].bp);
> > > + state->path.blk[0].bp = NULL;
> > > +
> > > + error = xfs_attr3_leaf_read(args->trans, args->dp, 0, -1, &bp);
> > > + if (error)
> > > + goto out;
> > > +
> > > + 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 */
> > > + if (error)
> > > + goto out;
> > > + } else
> > > + xfs_trans_brelse(args->trans, bp);
> > > + }
> > > +out:
> > > + if (state != NULL)
> > > + xfs_da_state_free(state);
> > > +
> > > + return error;
> > > +}
> > > +
> > > +/*
> > > + * Add a name to a Btree-format attribute list.
> > > + *
> > > + * This will involve walking down the Btree, and may involve splitting
> > > + * leaf nodes and even splitting intermediate nodes up to and including
> > > + * the root node (a special case of an intermediate node).
> > > + *
> > > + * "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
> > > + * -EGAIN 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_node_addname_later(
> > > + struct xfs_da_args *args)
> > > +{
> > > + struct xfs_da_state *state = NULL;
> > > + struct xfs_da_state_blk *blk;
> > > + struct xfs_inode *dp;
> > > + int retval, error = 0;
> > > + int nmap;
> > > + struct xfs_bmbt_irec *map = &args->dc.map;
> > > +
> > > + trace_xfs_attr_node_addname(args);
> > > +
> > > + /*
> > > + * Fill in bucket of arguments/results/context to carry around.
> > > + */
> > > + dp = args->dp;
> > > +
> > > + if (args->dc.flags & XFS_DC_FOUND_NBLK)
> > > + goto found_blk;
> > > +
> > > + /*
> > > + * Search to see if name already exists, and get back a pointer
> > > + * to where it should go.
> > > + */
> > > + retval = xfs_attr_node_hasname(args, &state);
> > > + blk = &state->path.blk[state->path.active-1];
> > > + ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> > > + if ((args->name.type & ATTR_REPLACE) && (retval == -ENOATTR)) {
> > > + goto out;
> > > + } else if (retval == -EEXIST) {
> > > + if (args->name.type & ATTR_CREATE)
> > > + goto out;
> > > +
> > > + trace_xfs_attr_node_replace(args);
> > > +
> > > + /* save the attribute state for later removal*/
> > > + args->op_flags |= XFS_DA_OP_RENAME; /* atomic rename op */
> > > + args->blkno2 = args->blkno; /* set 2nd entry info*/
> > > + args->index2 = args->index;
> > > + args->rmtblkno2 = args->rmtblkno;
> > > + args->rmtblkcnt2 = args->rmtblkcnt;
> > > + args->rmtvaluelen2 = args->rmtvaluelen;
> > > +
> > > + /*
> > > + * clear the remote attr state now that it is saved so that the
> > > + * values reflect the state of the attribute we are about to
> > > + * add, not the attribute we just found and will remove later.
> > > + */
> > > + args->rmtblkno = 0;
> > > + args->rmtblkcnt = 0;
> > > + args->rmtvaluelen = 0;
> > > + }
> > > +
> > > + retval = xfs_attr3_leaf_add(blk->bp, state->args);
> > > + if (retval == -ENOSPC) {
> > > + if (state->path.active == 1) {
> > > + /*
> > > + * Its really a single leaf node, but it had
> > > + * out-of-line values so it looked like it *might*
> > > + * have been a b-tree.
> > > + */
> > > + xfs_da_state_free(state);
> > > + state = NULL;
> > > + error = xfs_attr3_leaf_to_node(args);
> > > + if (error)
> > > + goto out;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + /*
> > > + * Split as many Btree elements as required.
> > > + * This code tracks the new and old attr's location
> > > + * in the index/blkno/rmtblkno/rmtblkcnt fields and
> > > + * in the index2/blkno2/rmtblkno2/rmtblkcnt2 fields.
> > > + */
> > > + error = xfs_da3_split(state);
> > > + if (error)
> > > + goto out;
> > > + } else {
> > > + /*
> > > + * Addition succeeded, update Btree hashvals.
> > > + */
> > > + xfs_da3_fixhashpath(state, &state->path);
> > > + }
> > > +
> > > + /*
> > > + * Kill the state structure, we're done with it and need to
> > > + * allow the buffers to come back later.
> > > + */
> > > + xfs_da_state_free(state);
> > > + state = NULL;
> > > +
> > > + args->dc.flags |= XFS_DC_FOUND_NBLK;
> > > + return -EAGAIN;
> > > +found_blk:
> > > +
> > > + /*
> > > + * 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) {
> > > + if (!(args->dc.flags & XFS_DC_ALLOC_NODE)) {
> > > + args->dc.flags |= XFS_DC_ALLOC_NODE;
> > > + args->dc.lblkno = 0;
> > > + args->dc.lfileoff = 0;
> > > + args->dc.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;
> > > +
> > > + args->dc.blkcnt = args->rmtblkcnt;
> > > + args->dc.lblkno = args->rmtblkno;
> > > + }
> > > + /*
> > > + * Roll through the "value", allocating blocks on disk as
> > > + * required.
> > > + */
> > > + while (args->dc.blkcnt > 0) {
> > > + nmap = 1;
> > > + error = xfs_bmapi_write(args->trans, dp,
> > > + (xfs_fileoff_t)args->dc.lblkno, args->dc.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 */
> > > + args->dc.lblkno += map->br_blockcount;
> > > + args->dc.blkcnt -= map->br_blockcount;
> > > +
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + error = xfs_attr_rmtval_set_value(args);
> > > + if (error)
> > > + return error;
> > > + }
> > > +
> > > + if (args->rmtblkno > 0) {
> > > + /*
> > > + * Added a "remote" value, just clear the incomplete flag.
> > > + */
> > > + error = xfs_attr3_leaf_clearflag(args);
> > > + if (error)
> > > + goto out;
> > > + }
> > > + retval = error = 0;
> > > +
> > > +out:
> > > + if (state)
> > > + xfs_da_state_free(state);
> > > + if (error)
> > > + return error;
> > > +
> > > + return retval;
> > > +}
> > > +
> > > +
> > > +
> > > +/*
> > > * Fill in the disk block numbers in the state structure for the buffers
> > > * that are attached to the state structure.
> > > * This is done so that we can quickly reattach ourselves to those buffers
> > > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > > index fb56d81..6203766 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.h
> > > +++ b/fs/xfs/libxfs/xfs_attr.h
> > > @@ -149,9 +149,11 @@ int xfs_attr_get(struct xfs_inode *ip, struct xfs_name *name,
> > > int xfs_attr_set(struct xfs_inode *dp, struct xfs_name *name,
> > > unsigned char *value, int valuelen);
> > > int xfs_attr_set_args(struct xfs_da_args *args);
> > > +int xfs_attr_set_later(struct xfs_da_args *args, struct xfs_buf **leaf_bp);
> > > int xfs_attr_remove(struct xfs_inode *dp, struct xfs_name *name);
> > > int xfs_has_attr(struct xfs_da_args *args);
> > > int xfs_attr_remove_args(struct xfs_da_args *args);
> > > +int xfs_attr_remove_later(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);
> > > --
> > > 2.7.4
> > >
