On Fri, 18 Dec 2020 00:29:06 -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 has become xfs_attr_remove_iter, which
> uses a sort of state machine like switch to keep track of where it was
> when EAGAIN was returned. xfs_attr_node_removename has also been
> modified to use the switch, and 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 | 218 +++++++++++++++++++++++++++++-----------
> fs/xfs/libxfs/xfs_attr.h | 100 ++++++++++++++++++
> 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, 288 insertions(+), 84 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 1969b88..b6330f9 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -53,7 +53,7 @@ STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
> */
> STATIC int xfs_attr_node_get(xfs_da_args_t *args);
> STATIC int xfs_attr_node_addname(xfs_da_args_t *args);
> -STATIC int xfs_attr_node_removename(xfs_da_args_t *args);
> +STATIC int xfs_attr_node_removename_iter(struct xfs_delattr_context *dac);
> STATIC int xfs_attr_node_hasname(xfs_da_args_t *args,
> struct xfs_da_state **state);
> STATIC int xfs_attr_fillstate(xfs_da_state_t *state);
> @@ -264,6 +264,34 @@ xfs_attr_set_shortform(
> }
>
> /*
> + * 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.
> + */
> +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);
> + if (error)
> + return error;
> + } else
> + error = xfs_trans_roll_inode(&args->trans, args->dp);
> +
> + return error;
> +}
> +
> +/*
> * Set the attribute specified in @args.
> */
> int
> @@ -364,23 +392,58 @@ xfs_has_attr(
> */
> int
> xfs_attr_remove_args(
> - struct xfs_da_args *args)
> + struct xfs_da_args *args)
> {
> - struct xfs_inode *dp = args->dp;
> - int error;
> + int error;
> + struct xfs_delattr_context dac = {
> + .da_args = 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;
> +}
>
> - if (!xfs_inode_hasattr(dp)) {
> - error = -ENOATTR;
> - } else if (dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL) {
> +/*
> + * Remove the attribute specified in @args.
> + *
> + * This function may return -EAGAIN to signal that the transaction needs to be
> + * rolled. Callers should continue calling this function until they receive a
> + * return value other than -EAGAIN.
> + */
> +int
> +xfs_attr_remove_iter(
> + struct xfs_delattr_context *dac)
> +{
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> +
> + /* If we are shrinking a node, resume shrink */
> + if (dac->dela_state == XFS_DAS_RM_SHRINK)
> + goto node;
> +
> + if (!xfs_inode_hasattr(dp))
> + return -ENOATTR;
> +
> + if (dp->i_afp->if_format == 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)) {
> - error = xfs_attr_leaf_removename(args);
> - } else {
> - error = xfs_attr_node_removename(args);
> + return xfs_attr_shortform_remove(args);
> }
>
> - return error;
> + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
> + return xfs_attr_leaf_removename(args);
> +node:
> + /* If we are not short form or leaf, then proceed to remove node */
> + return xfs_attr_node_removename_iter(dac);
> }
>
> /*
> @@ -1178,10 +1241,11 @@ 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)
> {
In xfs_attr_node_removename_setup(), if either of
xfs_attr_leaf_mark_incomplete() or xfs_attr_rmtval_invalidate() returns with a
non-zero value, the memory pointed to by dac->da_state is not freed. This
happens because the caller (i.e. xfs_attr_node_removename_iter()) checks for
the non-NULL value of its local variable "state" to actually free the
corresponding memory.
> - 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)
> @@ -1203,13 +1267,16 @@ int xfs_attr_node_removename_setup(
> }
>
> STATIC int
> -xfs_attr_node_remove_rmt(
> - struct xfs_da_args *args,
> - struct xfs_da_state *state)
> +xfs_attr_node_remove_rmt (
> + struct xfs_delattr_context *dac,
> + struct xfs_da_state *state)
> {
> - int error = 0;
> + int error = 0;
>
> - error = xfs_attr_rmtval_remove(args);
> + /*
> + * May return -EAGAIN to request that the caller recall this function
> + */
> + error = __xfs_attr_rmtval_remove(dac);
> if (error)
> return error;
>
> @@ -1240,28 +1307,34 @@ xfs_attr_node_remove_cleanup(
> }
>
> /*
> - * Remove a name from a B-tree attribute list.
> + * Step through removeing 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 either an inline 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_remove_step(
> - struct xfs_da_args *args,
> - struct xfs_da_state *state)
> + struct xfs_delattr_context *dac)
> {
> - int error;
> - struct xfs_inode *dp = args->dp;
> -
> -
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_da_state *state = dac->da_state;
> + int 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.
> */
> if (args->rmtblkno > 0) {
> - error = xfs_attr_node_remove_rmt(args, state);
> + /*
> + * May return -EAGAIN. Remove blocks until args->rmtblkno == 0
> + */
> + error = xfs_attr_node_remove_rmt(dac, state);
> if (error)
> return error;
> }
> @@ -1274,51 +1347,74 @@ xfs_attr_node_remove_step(
> *
> * This routine will find the blocks of the name to remove, remove them and
> * shrink the tree if needed.
> + *
> + * This routine is meant to function as either an inline 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)
> +xfs_attr_node_removename_iter(
> + struct xfs_delattr_context *dac)
> {
> - struct xfs_da_state *state = NULL;
> - int retval, error;
> - struct xfs_inode *dp = args->dp;
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_da_state *state = NULL;
> + 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;
> + if (!dac->da_state) {
> + error = xfs_attr_node_removename_setup(dac);
> + if (error)
> + goto out;
> + }
> + state = dac->da_state;
>
> - error = xfs_attr_node_remove_step(args, state);
> - if (error)
> - goto out;
> + switch (dac->dela_state) {
> + case XFS_DAS_UNINIT:
> + /*
> + * repeatedly remove remote blocks, remove the entry and join.
> + * returns -EAGAIN or 0 for completion of the step.
> + */
> + error = xfs_attr_node_remove_step(dac);
> + if (error)
> + break;
>
> - retval = xfs_attr_node_remove_cleanup(args, state);
> + 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)
> - return error;
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - return error;
> /*
> - * 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)
> - return error;
> - }
> + if (retval && (state->path.active > 1)) {
> + error = xfs_da3_join(state);
> + if (error)
> + return error;
>
> - /*
> - * 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..3154ef4 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -74,6 +74,102 @@ 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
> + * found attr blks? ───n──┐
> + * │ v
> + * │ find and invalidate
> + * y the blocks. mark
> + * │ attr incomplete
> + * ├────────────────┘
> + * │
> + * v
> + * remove a block with
> + * xfs_attr_node_remove_step <────┐
> + * │ │
> + * v │
> + * still have blks ──y──> return -EAGAIN.
> + * to remove? re-enter with one
> + * │ less blk to remove
> + * n
> + * │
> + * 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_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 +187,10 @@ 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..f09820c 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 dont 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 reminicent 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"
>
--
chandan
