Re: [PATCH RESEND v18 10/11] xfs: Add delay ready attr remove routines

Allison Henderson
2021-05-15T05:41:54Z

On 5/13/21 5:46 PM, Darrick J. Wong wrote:
> On Wed, May 12, 2021 at 09:14:07AM -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@oracle.com>
>> Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
>> Reviewed-by: Brian Foster <bfoster@redhat.com>
>> ---
>> fs/xfs/libxfs/xfs_attr.c | 213 ++++++++++++++++++++++++++++------------
>> fs/xfs/libxfs/xfs_attr.h | 131 ++++++++++++++++++++++++
>> 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, 314 insertions(+), 84 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
>> index 21f862e..a91fff6 100644
>> --- a/fs/xfs/libxfs/xfs_attr.c
>> +++ b/fs/xfs/libxfs/xfs_attr.c
>> @@ -57,7 +57,6 @@ 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_removename(xfs_da_args_t *args);
>> STATIC int xfs_attr_node_addname_clear_incomplete(struct xfs_da_args *args);
>> STATIC int xfs_attr_node_hasname(xfs_da_args_t *args,
>> struct xfs_da_state **state);
>> @@ -241,6 +240,31 @@ xfs_attr_is_shortform(
>> ip->i_afp->if_nextents == 0);
>> }
>>
>> +/*
>> + * Checks to see if a delayed attribute transaction should be rolled. If so,
>> + * transaction is finished or rolled as needed.
>> + */
>> +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)
>> @@ -544,16 +568,25 @@ xfs_has_attr(
>> */
>> int
>> xfs_attr_remove_args(
>> - struct xfs_da_args *args)
>> + struct xfs_da_args *args)
>> {
>> - if (!xfs_inode_hasattr(args->dp))
>> - return -ENOATTR;
>> + int error;
>> + struct xfs_delattr_context dac = {
>> + .da_args = args,
>> + };
>>
>> - if (args->dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL)
>> - return xfs_attr_shortform_remove(args);
>> - if (xfs_attr_is_leaf(args->dp))
>> - return xfs_attr_leaf_removename(args);
>> - return xfs_attr_node_removename(args);
>> + do {
>> + error = xfs_attr_remove_iter(&dac);
>> + if (error != -EAGAIN)
>> + break;
>> +
>> + error = xfs_attr_trans_roll(&dac);
>> + if (error)
>> + return error;
>> +
>> + } while (true);
>> +
>> + return error;
>> }
>>
>> /*
>> @@ -1197,14 +1230,16 @@ xfs_attr_leaf_mark_incomplete(
>> */
>> STATIC
>> int xfs_attr_node_removename_setup(
>> - struct xfs_da_args *args,
>> - struct xfs_da_state **state)
>> + struct xfs_delattr_context *dac)
>> {
>> - int error;
>> + struct xfs_da_args *args = dac->da_args;
>> + struct xfs_da_state **state = &dac->da_state;
>> + int error;
>>
>> error = xfs_attr_node_hasname(args, state);
>> if (error != -EEXIST)
>> return error;
>> + error = 0;
>>
>> ASSERT((*state)->path.blk[(*state)->path.active - 1].bp != NULL);
>> ASSERT((*state)->path.blk[(*state)->path.active - 1].magic ==
>> @@ -1213,12 +1248,15 @@ int xfs_attr_node_removename_setup(
>> if (args->rmtblkno > 0) {
>> error = xfs_attr_leaf_mark_incomplete(args, *state);
>> if (error)
>> - return error;
>> + goto out;
>>
>> - return xfs_attr_rmtval_invalidate(args);
>> + error = xfs_attr_rmtval_invalidate(args);
>> }
>> +out:
>> + if (error)
>> + xfs_da_state_free(*state);
>>
>> - return 0;
>> + return error;
>> }
>>
>> STATIC int
>> @@ -1241,70 +1279,123 @@ xfs_attr_node_remove_name(
>> }
>>
>> /*
>> - * 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;
>> + /*
>> + * Shortform or leaf formats don't require transaction rolls and
>> + * thus state transitions. Call the right helper and return.
>> + */
>> + if (dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL)
>> + return xfs_attr_shortform_remove(args);
>> +
>> + if (xfs_attr_is_leaf(dp))
>> + return xfs_attr_leaf_removename(args);
>>
>> /*
>> - * Refill the state structure with buffers, the prior calls
>> - * released our buffers.
>> + * Node format may require transaction rolls. Set up the
>> + * state context and fall into the state machine.
>> */
>> - error = xfs_attr_refillstate(state);
>> - if (error)
>> - goto out;
>> - }
>> - retval = xfs_attr_node_remove_name(args, state);
>> + if (!dac->da_state) {
>> + error = xfs_attr_node_removename_setup(dac);
>> + if (error)
>> + return error;
>> + state = dac->da_state;
>> + }
>> +
>> + /* fallthrough */
>> + case XFS_DAS_RMTBLK:
>> + dac->dela_state = XFS_DAS_RMTBLK;
>>
>> - /*
>> - * 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.
>> + * 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_trans_roll_inode(&args->trans, dp);
>> - if (error)
>> - goto out;
>> - }
>> + if (args->rmtblkno > 0) {
>> + /*
>> + * May return -EAGAIN. Roll and repeat until all remote
>> + * blocks are removed.
>> + */
>> + error = __xfs_attr_rmtval_remove(dac);
>> + if (error == -EAGAIN)
>> + return error;
>> + else if (error)
>> + goto out;
>>
>> - /*
>> - * If the result is small enough, push it all into the inode.
>> - */
>> - if (xfs_attr_is_leaf(dp))
>> - error = xfs_attr_node_shrink(args, state);
>> + /*
>> + * Refill the state structure with buffers (the prior
>> + * calls released our buffers) and close out this
>> + * transaction before proceeding.
>> + */
>> + ASSERT(args->rmtblkno == 0);
>> + error = xfs_attr_refillstate(state);
>> + if (error)
>> + goto out;
>> + dac->dela_state = XFS_DAS_RM_NAME;
>> + dac->flags |= XFS_DAC_DEFER_FINISH;
>> + return -EAGAIN;
>> + }
>> +
>> + /* fallthrough */
>> + case XFS_DAS_RM_NAME:
>> + retval = xfs_attr_node_remove_name(args, state);
>
> Hm. I see a bunch of cleanup possibilities for after this series...
>
> xfs_attr_shortform_remove
> xfs_attr_leaf_removename
> xfs_attr_node_remove_name
>
> Can you add a patch to the end of the series renaming these to
> xfs_attr_{sf,leaf,node}_removename or something?
>
> Also, can you refactor the chunk of code under "Remove the name and
> update the hashvals in the tree" in
> xfs_attr_node_addname_clear_incomplete to use xfs_attr_node_remove_name?
>
> (Separate cleanup patches at the end of the series would be appreciated.)
Sure, that should be fine. Do you want a patch for each? Or just one
clean up patch?

>
>>
>> + /*
>> + * Check to see if the tree needs to be collapsed. If so, roll
>> + * the transacton and fall into the shrink state.
>> + */
>> + if (retval && (state->path.active > 1)) {
>> + error = xfs_da3_join(state);
>> + if (error)
>> + goto out;
>> +
>> + 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.
>> + * This is our final state so it's safe to return a dirty
>> + * transaction.
>> + */
>> + if (xfs_attr_is_leaf(dp))
>> + error = xfs_attr_node_shrink(args, state);
>> + ASSERT(error != -EAGAIN);
>> + break;
>> + default:
>> + ASSERT(0);
>> + error = -EINVAL;
>> + goto out;
>> + }
>> 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 2b1f619..32736d9 100644
>> --- a/fs/xfs/libxfs/xfs_attr.h
>> +++ b/fs/xfs/libxfs/xfs_attr.h
>> @@ -74,6 +74,133 @@ 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────┐
>
> Nit: This should be "attr has remote blks?" since everywhere else in the
> code we call them remote value blocks.
Ok, will fix
>
>> + * │ │ v
>> + * │ │ find and invalidate
>> + * │ y the blocks. mark
>
> remote blocks...
will fix

>
>> + * │ │ attr incomplete
>> + * │ ├────────────────┘
>> + * └──────────┤
>> + * │
>> + * v
>> + * Have blks to remove? ───y─────────┐
>> + * │ ^ remove the blks
>
> remote blocks...
will fix

>
>> + * │ │ │
>> + * │ │ v
>> + * │ XFS_DAS_RMTBLK <─n── done?
>> + * │ re-enter with │
>> + * │ one less blk to y
>> + * │ remove │
>> + * │ V
>> + * │ refill the state
>> + * n │
>> + * │ v
>> + * │ XFS_DAS_RM_NAME
>> + * │ │
>> + * ├─────────────────────────┘
>> + * │
>> + * 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
>
> nit: s/recall/call the subroutine again/
Sure, will update

>
>> + * 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_NAME, /* Remove attr name */
>> + 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.
>> *========================================================================*/
>> @@ -92,6 +219,10 @@ 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 556184b..d97de20 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..2f3c4cc 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 && 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
>
> "Callers should keep calling this routine until it returns something
> other than -EAGAIN."
>
> Also, that should go in the comment above the function.
Alrighty, will update
>
> With all those fairly minor things fixed,
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>
Thanks!
Allison

> --D
>
>> + * 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
>>