On Fri, Apr 02, 2021 at 02:42:28AM -0700, Allison Henderson wrote:
>
>
> On 4/1/21 9:55 AM, Brian Foster wrote:
> > On Thu, Mar 25, 2021 at 05:33:07PM -0700, Allison Henderson wrote:
> > > This patch modifies the attr remove routines to be delay ready. This
> > > means they no longer roll or commit transactions, but instead return
> > > -EAGAIN to have the calling routine roll and refresh the transaction. In
> > > this series, xfs_attr_remove_args is merged with
> > > xfs_attr_node_removename become a new function, xfs_attr_remove_iter.
> > > This new version uses a sort of state machine like switch to keep track
> > > of where it was when EAGAIN was returned. A new version of
> > > xfs_attr_remove_args consists of a simple loop to refresh the
> > > transaction until the operation is completed. A new XFS_DAC_DEFER_FINISH
> > > flag is used to finish the transaction where ever the existing code used
> > > to.
> > >
> > > Calls to xfs_attr_rmtval_remove are replaced with the delay ready
> > > version __xfs_attr_rmtval_remove. We will rename
> > > __xfs_attr_rmtval_remove back to xfs_attr_rmtval_remove when we are
> > > done.
> > >
> > > xfs_attr_rmtval_remove itself is still in use by the set routines (used
> > > during a rename). For reasons of preserving existing function, we
> > > modify xfs_attr_rmtval_remove to call xfs_defer_finish when the flag is
> > > set. Similar to how xfs_attr_remove_args does here. Once we transition
> > > the set routines to be delay ready, xfs_attr_rmtval_remove is no longer
> > > used and will be removed.
> > >
> > > This patch also adds a new struct xfs_delattr_context, which we will use
> > > to keep track of the current state of an attribute operation. The new
> > > xfs_delattr_state enum is used to track various operations that are in
> > > progress so that we know not to repeat them, and resume where we left
> > > off before EAGAIN was returned to cycle out the transaction. Other
> > > members take the place of local variables that need to retain their
> > > values across multiple function recalls. See xfs_attr.h for a more
> > > detailed diagram of the states.
> > >
> > > Signed-off-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
> > > ---
> > > fs/xfs/libxfs/xfs_attr.c | 206 +++++++++++++++++++++++++++-------------
> > > fs/xfs/libxfs/xfs_attr.h | 125 ++++++++++++++++++++++++
> > > fs/xfs/libxfs/xfs_attr_leaf.c | 2 +-
> > > fs/xfs/libxfs/xfs_attr_remote.c | 48 ++++++----
> > > fs/xfs/libxfs/xfs_attr_remote.h | 2 +-
> > > fs/xfs/xfs_attr_inactive.c | 2 +-
> > > 6 files changed, 297 insertions(+), 88 deletions(-)
> > >
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index 41accd5..4a73691 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > ...
> > > @@ -221,6 +220,32 @@ xfs_attr_is_shortform(
> > > ip->i_afp->if_nextents == 0);
> > > }
> > > +/*
> > > + * Checks to see if a delayed attribute transaction should be rolled. If so,
> > > + * also checks for a defer finish. Transaction is finished and rolled as
> > > + * needed, and returns true of false if the delayed operation should continue.
> > > + */
> >
> > Outdated comment wrt to the return value.
> Ok, will drop last line here
>
> >
> > > +int
> > > +xfs_attr_trans_roll(
> > > + struct xfs_delattr_context *dac)
> > > +{
> > > + struct xfs_da_args *args = dac->da_args;
> > > + int error;
> > > +
> > > + if (dac->flags & XFS_DAC_DEFER_FINISH) {
> > > + /*
> > > + * The caller wants us to finish all the deferred ops so that we
> > > + * avoid pinning the log tail with a large number of deferred
> > > + * ops.
> > > + */
> > > + dac->flags &= ~XFS_DAC_DEFER_FINISH;
> > > + error = xfs_defer_finish(&args->trans);
> > > + } else
> > > + error = xfs_trans_roll_inode(&args->trans, args->dp);
> > > +
> > > + return error;
> > > +}
> > > +
> > > STATIC int
> > > xfs_attr_set_fmt(
> > > struct xfs_da_args *args)
> > ...
> > > @@ -1232,70 +1264,114 @@ xfs_attr_node_remove_cleanup(
> > > }
> > > /*
> > > - * Remove a name from a B-tree attribute list.
> > > + * Remove the attribute specified in @args.
> > > *
> > > * 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 either an in-line or 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_removename(
> > > - struct xfs_da_args *args)
> > > +int
> > > +xfs_attr_remove_iter(
> > > + struct xfs_delattr_context *dac)
> > > {
> > > - struct xfs_da_state *state;
> > > - int retval, error;
> > > - struct xfs_inode *dp = args->dp;
> > > + struct xfs_da_args *args = dac->da_args;
> > > + struct xfs_da_state *state = dac->da_state;
> > > + int retval, error;
> > > + struct xfs_inode *dp = args->dp;
> > > trace_xfs_attr_node_removename(args);
> > > - error = xfs_attr_node_removename_setup(args, &state);
> > > - if (error)
> > > - goto out;
> > > + switch (dac->dela_state) {
> > > + case XFS_DAS_UNINIT:
> > > + if (!xfs_inode_hasattr(dp))
> > > + return -ENOATTR;
> > > - /*
> > > - * 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.
> > > - */
> > > - if (args->rmtblkno > 0) {
> > > - error = xfs_attr_rmtval_remove(args);
> > > - if (error)
> > > - goto out;
> > > + if (dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL) {
> > > + ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> > > + return xfs_attr_shortform_remove(args);
> > > + }
> > > +
> > > + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
> > > + return xfs_attr_leaf_removename(args);
> > > +
> > > + /* fallthrough */
> > > + case XFS_DAS_RMTBLK:
> > > + dac->dela_state = XFS_DAS_RMTBLK;
> > > +
> > > + if (!dac->da_state) {
> > > + error = xfs_attr_node_removename_setup(dac);
> > > + if (error)
> > > + goto out;
> >
> > Do we need the goto here if _removename_setup() frees state on error (or
> > is the latter change necessary)?
> I think we can safely return here. Will update
>
> >
> > > + }
> > > + state = dac->da_state;
> >
> > Also, can this fold into the above if (!da_state) branch? Or maybe the
> > whole setup branch pulled up into the UNINIT state? Not a big deal, but
> > it does look a little out of place in the RMTBLK state.
> Sure, it should be ok, there isnt any EAGAINs here, so it shouldnt make a
> difference
>
> >
> > > /*
> > > - * Refill the state structure with buffers, the prior calls
> > > - * released our buffers.
> > > + * 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.
> > > */
> > > - error = xfs_attr_refillstate(state);
> > > - if (error)
> > > - goto out;
> > > - }
> > > - retval = xfs_attr_node_remove_cleanup(args, state);
> > > + if (args->rmtblkno > 0) {
> > > + /*
> > > + * May return -EAGAIN. Remove blocks until
> > > + * args->rmtblkno == 0
> > > + */
> > > + error = __xfs_attr_rmtval_remove(dac);
> > > + if (error)
> > > + break;
> >
> > I feel that the difference between a break and goto out might confuse
> > some of the error handling. Right now, it looks like the exit path
> > handles either scenario, so we could presumably do something like the
> > following at the end of the function:
> >
> > if (error != -EAGAIN && state)
> > xfs_da_state_free(state);
> > return error;
> >
> > ... and just ditch the label. Alternatively we could retain the label above
> > the state check, but just use it consistently throughout the function.
> >
> Either will work? I think I'd prefer the gotos over the breaks though, I
> just think it reads easier. The switch is sort of big, so I think the gotos
> make it a little more clear in that we're exiting the function without
> having to skim all the way to the bottom.
>
Sounds reasonable to me as long as the error handling usage is
consistent. Thanks.
Brian
> > Other than those few nits, this one looks pretty good to me.
> Great, will update. Thanks!
>
> Allison
>
> >
> > Brian
> >
> > > +
> > > + /*
> > > + * Refill the state structure with buffers, the prior
> > > + * calls released our buffers.
> > > + */
> > > + ASSERT(args->rmtblkno == 0);
> > > + error = xfs_attr_refillstate(state);
> > > + if (error)
> > > + goto out;
> > > +
> > > + dac->flags |= XFS_DAC_DEFER_FINISH;
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + retval = xfs_attr_node_remove_cleanup(args, state);
> > > - /*
> > > - * Check to see if the tree needs to be collapsed.
> > > - */
> > > - if (retval && (state->path.active > 1)) {
> > > - error = xfs_da3_join(state);
> > > - if (error)
> > > - goto out;
> > > - error = xfs_defer_finish(&args->trans);
> > > - if (error)
> > > - goto out;
> > > /*
> > > - * Commit the Btree join operation and start a new trans.
> > > + * Check to see if the tree needs to be collapsed. Set the flag
> > > + * to indicate that the calling function needs to move the
> > > + * shrink operation
> > > */
> > > - error = xfs_trans_roll_inode(&args->trans, dp);
> > > - if (error)
> > > - goto out;
> > > - }
> > > + if (retval && (state->path.active > 1)) {
> > > + error = xfs_da3_join(state);
> > > + if (error)
> > > + goto out;
> > > - /*
> > > - * If the result is small enough, push it all into the inode.
> > > - */
> > > - if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
> > > - error = xfs_attr_node_shrink(args, state);
> > > + dac->flags |= XFS_DAC_DEFER_FINISH;
> > > + dac->dela_state = XFS_DAS_RM_SHRINK;
> > > + return -EAGAIN;
> > > + }
> > > +
> > > + /* fallthrough */
> > > + case XFS_DAS_RM_SHRINK:
> > > + /*
> > > + * If the result is small enough, push it all into the inode.
> > > + */
> > > + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
> > > + error = xfs_attr_node_shrink(args, state);
> > > +
> > > + break;
> > > + default:
> > > + ASSERT(0);
> > > + error = -EINVAL;
> > > + goto out;
> > > + }
> > > + if (error == -EAGAIN)
> > > + return error;
> > > out:
> > > if (state)
> > > xfs_da_state_free(state);
> > > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > > index 3e97a93..92a6a50 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.h
> > > +++ b/fs/xfs/libxfs/xfs_attr.h
> > > @@ -74,6 +74,127 @@ struct xfs_attr_list_context {
> > > };
> > > +/*
> > > + * ========================================================================
> > > + * Structure used to pass context around among the delayed routines.
> > > + * ========================================================================
> > > + */
> > > +
> > > +/*
> > > + * Below is a state machine diagram for attr remove operations. The XFS_DAS_*
> > > + * states indicate places where the function would return -EAGAIN, and then
> > > + * immediately resume from after being recalled by the calling function. States
> > > + * marked as a "subroutine state" indicate that they belong to a subroutine, and
> > > + * so the calling function needs to pass them back to that subroutine to allow
> > > + * it to finish where it left off. But they otherwise do not have a role in the
> > > + * calling function other than just passing through.
> > > + *
> > > + * xfs_attr_remove_iter()
> > > + * │
> > > + * v
> > > + * have attr to remove? ──n──> done
> > > + * │
> > > + * y
> > > + * │
> > > + * v
> > > + * are we short form? ──y──> xfs_attr_shortform_remove ──> done
> > > + * │
> > > + * n
> > > + * │
> > > + * V
> > > + * are we leaf form? ──y──> xfs_attr_leaf_removename ──> done
> > > + * │
> > > + * n
> > > + * │
> > > + * V
> > > + * ┌── need to setup state?
> > > + * │ │
> > > + * n y
> > > + * │ │
> > > + * │ v
> > > + * │ find attr and get state
> > > + * │ attr has blks? ───n────???
> > > + * │ │ v
> > > + * │ │ find and invalidate
> > > + * │ y the blocks. mark
> > > + * │ │ attr incomplete
> > > + * │ ├────────────────┘
> > > + * └──────────┤
> > > + * │
> > > + * v
> > > + * Have blks to remove? ─────y────???
> > > + * │ ^ remove the blks
> > > + * │ │ │
> > > + * │ │ v
> > > + * │ │ refill the state
> > > + * n │ │
> > > + * │ │ v
> > > + * │ │ XFS_DAS_RMTBLK
> > > + * │ └───── re-enter with one
> > > + * │ less blk to remove
> > > + * │
> > > + * v
> > > + * remove leaf and
> > > + * update hash with
> > > + * xfs_attr_node_remove_cleanup
> > > + * │
> > > + * v
> > > + * need to
> > > + * shrink tree? ─n─???
> > > + * │ │
> > > + * y │
> > > + * │ │
> > > + * v │
> > > + * join leaf │
> > > + * │ │
> > > + * v │
> > > + * XFS_DAS_RM_SHRINK │
> > > + * │ │
> > > + * v │
> > > + * do the shrink │
> > > + * │ │
> > > + * v │
> > > + * free state <──┘
> > > + * │
> > > + * v
> > > + * done
> > > + *
> > > + */
> > > +
> > > +/*
> > > + * Enum values for xfs_delattr_context.da_state
> > > + *
> > > + * These values are used by delayed attribute operations to keep track of where
> > > + * they were before they returned -EAGAIN. A return code of -EAGAIN signals the
> > > + * calling function to roll the transaction, and then recall the subroutine to
> > > + * finish the operation. The enum is then used by the subroutine to jump back
> > > + * to where it was and resume executing where it left off.
> > > + */
> > > +enum xfs_delattr_state {
> > > + 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 */
> > > +};
> > > +
> > > +/*
> > > + * Defines for xfs_delattr_context.flags
> > > + */
> > > +#define XFS_DAC_DEFER_FINISH 0x01 /* finish the transaction */
> > > +
> > > +/*
> > > + * Context used for keeping track of delayed attribute operations
> > > + */
> > > +struct xfs_delattr_context {
> > > + struct xfs_da_args *da_args;
> > > +
> > > + /* Used in xfs_attr_node_removename to roll through removing blocks */
> > > + struct xfs_da_state *da_state;
> > > +
> > > + /* Used to keep track of current state of delayed operation */
> > > + unsigned int flags;
> > > + enum xfs_delattr_state dela_state;
> > > +};
> > > +
> > > /*========================================================================
> > > * Function prototypes for the kernel.
> > > *========================================================================*/
> > > @@ -91,6 +212,10 @@ int xfs_attr_set(struct xfs_da_args *args);
> > > int xfs_attr_set_args(struct xfs_da_args *args);
> > > int xfs_has_attr(struct xfs_da_args *args);
> > > int xfs_attr_remove_args(struct xfs_da_args *args);
> > > +int xfs_attr_remove_iter(struct xfs_delattr_context *dac);
> > > +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);
> > > #endif /* __XFS_ATTR_H__ */
> > > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> > > index d6ef69a..3780141 100644
> > > --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> > > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> > > @@ -19,8 +19,8 @@
> > > #include "xfs_bmap_btree.h"
> > > #include "xfs_bmap.h"
> > > #include "xfs_attr_sf.h"
> > > -#include "xfs_attr_remote.h"
> > > #include "xfs_attr.h"
> > > +#include "xfs_attr_remote.h"
> > > #include "xfs_attr_leaf.h"
> > > #include "xfs_error.h"
> > > #include "xfs_trace.h"
> > > diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
> > > index 48d8e9c..908521e7 100644
> > > --- a/fs/xfs/libxfs/xfs_attr_remote.c
> > > +++ b/fs/xfs/libxfs/xfs_attr_remote.c
> > > @@ -674,10 +674,12 @@ xfs_attr_rmtval_invalidate(
> > > */
> > > int
> > > xfs_attr_rmtval_remove(
> > > - struct xfs_da_args *args)
> > > + struct xfs_da_args *args)
> > > {
> > > - int error;
> > > - int retval;
> > > + int error;
> > > + struct xfs_delattr_context dac = {
> > > + .da_args = args,
> > > + };
> > > trace_xfs_attr_rmtval_remove(args);
> > > @@ -685,31 +687,29 @@ xfs_attr_rmtval_remove(
> > > * Keep de-allocating extents until the remote-value region is gone.
> > > */
> > > do {
> > > - retval = __xfs_attr_rmtval_remove(args);
> > > - if (retval && retval != -EAGAIN)
> > > - return retval;
> > > + error = __xfs_attr_rmtval_remove(&dac);
> > > + if (error != -EAGAIN)
> > > + break;
> > > - /*
> > > - * Close out trans and start the next one in the chain.
> > > - */
> > > - error = xfs_trans_roll_inode(&args->trans, args->dp);
> > > + error = xfs_attr_trans_roll(&dac);
> > > if (error)
> > > return error;
> > > - } while (retval == -EAGAIN);
> > > + } while (true);
> > > - return 0;
> > > + 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
> > > + * buffer that it is stored on. Returns -EAGAIN for the caller to refresh the
> > > * transaction and re-call the function
> > > */
> > > int
> > > __xfs_attr_rmtval_remove(
> > > - struct xfs_da_args *args)
> > > + struct xfs_delattr_context *dac)
> > > {
> > > - int error, done;
> > > + struct xfs_da_args *args = dac->da_args;
> > > + int error, done;
> > > /*
> > > * Unmap value blocks for this attr.
> > > @@ -719,12 +719,20 @@ __xfs_attr_rmtval_remove(
> > > if (error)
> > > return error;
> > > - error = xfs_defer_finish(&args->trans);
> > > - if (error)
> > > - return error;
> > > -
> > > - if (!done)
> > > + /*
> > > + * We don't need an explicit state here to pick up where we left off. We
> > > + * can figure it out using the !done return code. Calling function only
> > > + * needs to keep recalling this routine until we indicate to stop by
> > > + * returning anything other than -EAGAIN. The actual value of
> > > + * attr->xattri_dela_state may be some value reminiscent of the calling
> > > + * function, but it's value is irrelevant with in the context of this
> > > + * function. Once we are done here, the next state is set as needed
> > > + * by the parent
> > > + */
> > > + if (!done) {
> > > + dac->flags |= XFS_DAC_DEFER_FINISH;
> > > return -EAGAIN;
> > > + }
> > > return error;
> > > }
> > > diff --git a/fs/xfs/libxfs/xfs_attr_remote.h b/fs/xfs/libxfs/xfs_attr_remote.h
> > > index 9eee615..002fd30 100644
> > > --- a/fs/xfs/libxfs/xfs_attr_remote.h
> > > +++ b/fs/xfs/libxfs/xfs_attr_remote.h
> > > @@ -14,5 +14,5 @@ int xfs_attr_rmtval_remove(struct xfs_da_args *args);
> > > int xfs_attr_rmtval_stale(struct xfs_inode *ip, struct xfs_bmbt_irec *map,
> > > xfs_buf_flags_t incore_flags);
> > > int xfs_attr_rmtval_invalidate(struct xfs_da_args *args);
> > > -int __xfs_attr_rmtval_remove(struct xfs_da_args *args);
> > > +int __xfs_attr_rmtval_remove(struct xfs_delattr_context *dac);
> > > #endif /* __XFS_ATTR_REMOTE_H__ */
> > > diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c
> > > index bfad669..aaa7e66 100644
> > > --- a/fs/xfs/xfs_attr_inactive.c
> > > +++ b/fs/xfs/xfs_attr_inactive.c
> > > @@ -15,10 +15,10 @@
> > > #include "xfs_da_format.h"
> > > #include "xfs_da_btree.h"
> > > #include "xfs_inode.h"
> > > +#include "xfs_attr.h"
> > > #include "xfs_attr_remote.h"
> > > #include "xfs_trans.h"
> > > #include "xfs_bmap.h"
> > > -#include "xfs_attr.h"
> > > #include "xfs_attr_leaf.h"
> > > #include "xfs_quota.h"
> > > #include "xfs_dir2.h"
> > > --
> > > 2.7.4
> > >
> >
>
