On Saturday, April 4, 2020 3:42 AM Allison Collins 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.
>
> Two new helper functions have been added: xfs_attr_rmtval_set_init 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.
>
> Below is a state machine diagram for attr set 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_set_iter()
> │
> v
> need to upgrade
> from sf to leaf? ──n─┐
> │ │
> y │
> │ │
> V │
> XFS_DAS_ADD_LEAF │
> │ │
> v │
> ┌──────n── fork has <──────┘
> │ only 1 blk?
> │ │
> │ y
> │ │
> │ v
> │ xfs_attr_leaf_try_add()
> │ │
> │ v
> │ had enough
> ├──────n── space?
> │ │
> │ y
> │ │
> │ v
> │ XFS_DAS_FOUND_LBLK ──┐
> │ │
> │ XFS_DAS_FLIP_LFLAG ──┤
> │ (subroutine state) │
> │ │
> │ XFS_DAS_ALLOC_LEAF ──┤
> │ (subroutine state) │
> │ └─>xfs_attr_leaf_addname()
> │ │
> │ v
> │ ┌─────n── need to
> │ │ alloc blks?
> │ │ │
> │ │ y
> │ │ │
> │ │ v
> │ │ ┌─>XFS_DAS_ALLOC_LEAF
> │ │ │ │
> │ │ │ v
> │ │ └──y── need to alloc
> │ │ more blocks?
> │ │ │
> │ │ n
> │ │ │
> │ │ v
> │ │ was this
> │ └────────> a rename? ──n─┐
> │ │ │
> │ y │
> │ │ │
> │ v │
> │ flip incomplete │
> │ flag │
> │ │ │
> │ v │
> │ XFS_DAS_FLIP_LFLAG │
> │ │ │
> │ v │
> │ remove │
> │ XFS_DAS_RM_LBLK ─> old name │
> │ ^ │ │
> │ │ v │
> │ └──────y── more to │
> │ remove │
> │ │ │
> │ n │
> │ │ │
> │ v │
> │ done <──────┘
> └────> XFS_DAS_LEAF_TO_NODE ─┐
> │
> XFS_DAS_FOUND_NBLK ──┤
> (subroutine state) │
> │
> XFS_DAS_ALLOC_NODE ──┤
> (subroutine state) │
> │
> XFS_DAS_FLIP_NFLAG ──┤
> (subroutine state) │
> │
> └─>xfs_attr_node_addname()
> │
> v
> find space to store
> attr. Split if needed
> │
> v
> XFS_DAS_FOUND_NBLK
> │
> v
> ┌─────n── need to
> │ alloc blks?
> │ │
> │ y
> │ │
> │ v
> │ ┌─>XFS_DAS_ALLOC_NODE
> │ │ │
> │ │ v
> │ └──y── need to alloc
> │ more blocks?
> │ │
> │ n
> │ │
> │ v
> │ was this
> └────────> a rename? ──n─┐
> │ │
> y │
> │ │
> v │
> flip incomplete │
> flag │
> │ │
> v │
> XFS_DAS_FLIP_NFLAG │
> │ │
> v │
> remove │
> XFS_DAS_RM_NBLK ─> old name │
> ^ │ │
> │ v │
> └──────y── more to │
> remove │
> │ │
> n │
> │ │
> v │
> done <──────┘
>
> Signed-off-by: Allison Collins <allison.henderson@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_attr.c | 384 +++++++++++++++++++++++++++-------------
> fs/xfs/libxfs/xfs_attr.h | 16 ++
> fs/xfs/libxfs/xfs_attr_leaf.c | 1 +
> fs/xfs/libxfs/xfs_attr_remote.c | 111 +++++++-----
> fs/xfs/libxfs/xfs_attr_remote.h | 4 +
> fs/xfs/xfs_attr_inactive.c | 1 +
> fs/xfs/xfs_trace.h | 1 -
> 7 files changed, 351 insertions(+), 167 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index f700976..c160b7a 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -44,7 +44,7 @@ STATIC int xfs_attr_shortform_addname(xfs_da_args_t *args);
> * Internal routines when attribute list is one block.
> */
> STATIC int xfs_attr_leaf_get(xfs_da_args_t *args);
> -STATIC int xfs_attr_leaf_addname(xfs_da_args_t *args);
> +STATIC int xfs_attr_leaf_addname(struct xfs_delattr_context *dac);
> STATIC int xfs_attr_leaf_removename(struct xfs_delattr_context *dac);
> STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
>
> @@ -52,12 +52,13 @@ STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
> * Internal routines when attribute list is more than one block.
> */
> 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_addname(struct xfs_delattr_context *dac);
> STATIC int xfs_attr_node_removename(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);
> STATIC int xfs_attr_refillstate(xfs_da_state_t *state);
> +STATIC int xfs_attr_leaf_try_add(struct xfs_da_args *args, struct xfs_buf *bp);
>
> STATIC void
> xfs_delattr_context_init(
> @@ -227,8 +228,11 @@ xfs_attr_is_shortform(
>
> /*
> * Attempts to set an attr in shortform, or converts the tree to leaf form if
> - * there is not enough room. If the attr is set, the transaction is committed
> - * and set to NULL.
> + * there is not enough room. This function is meant to operate as a helper
> + * routine to the delayed attribute functions. It returns -EAGAIN to indicate
> + * that the calling function should roll the transaction, and then proceed to
> + * add the attr in leaf form. This subroutine does not expect to be recalled
> + * again like the other delayed attr routines do.
> */
> STATIC int
> xfs_attr_set_shortform(
> @@ -236,16 +240,16 @@ xfs_attr_set_shortform(
> struct xfs_buf **leaf_bp)
> {
> struct xfs_inode *dp = args->dp;
> - int error, error2 = 0;
> + int error = 0;
>
> /*
> * Try to add the attr to the attribute list in the inode.
> */
> error = xfs_attr_try_sf_addname(dp, args);
> +
> + /* Should only be 0, -EEXIST or ENOSPC */
> if (error != -ENOSPC) {
> - error2 = xfs_trans_commit(args->trans);
> - args->trans = NULL;
> - return error ? error : error2;
> + return error;
> }
> /*
> * It won't fit in the shortform, transform to a leaf block. GROT:
> @@ -258,18 +262,10 @@ xfs_attr_set_shortform(
> /*
> * 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. Once we're done rolling the transaction we
> - * can release the hold and add the attr to the leaf.
> + * 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);
> - return error;
> - }
> -
> - return 0;
> + return -EAGAIN;
> }
>
> /*
> @@ -279,9 +275,83 @@ int
> xfs_attr_set_args(
> struct xfs_da_args *args)
> {
> - struct xfs_inode *dp = args->dp;
> - struct xfs_buf *leaf_bp = NULL;
> - int error = 0;
> + struct xfs_buf *leaf_bp = NULL;
> + int error = 0;
> + struct xfs_delattr_context dac;
> +
> + xfs_delattr_context_init(&dac, args);
> +
> + do {
> + error = xfs_attr_set_iter(&dac, &leaf_bp);
> + if (error != -EAGAIN)
> + break;
> +
> + if (dac.flags & XFS_DAC_DEFER_FINISH) {
> + dac.flags &= ~XFS_DAC_DEFER_FINISH;
> + error = xfs_defer_finish(&args->trans);
> + if (error)
> + break;
> + }
> +
> + error = xfs_trans_roll_inode(&args->trans, args->dp);
> + if (error)
> + break;
> +
> + if (leaf_bp) {
> + xfs_trans_bjoin(args->trans, leaf_bp);
> + xfs_trans_bhold(args->trans, leaf_bp);
> + }
> +
> + } while (true);
> +
> + return error;
> +}
> +
> +/*
> + * 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_iter(
> + struct xfs_delattr_context *dac,
> + struct xfs_buf **leaf_bp)
> +{
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_inode *dp = args->dp;
> + int error = 0;
> + int sf_size;
> +
> + /* State machine switch */
> + switch (dac->dela_state) {
> + case XFS_DAS_ADD_LEAF:
> + goto das_add_leaf;
> + case XFS_DAS_ALLOC_LEAF:
> + case XFS_DAS_FLIP_LFLAG:
> + case XFS_DAS_FOUND_LBLK:
> + goto das_leaf;
> + case XFS_DAS_FOUND_NBLK:
> + case XFS_DAS_FLIP_NFLAG:
> + case XFS_DAS_ALLOC_NODE:
> + case XFS_DAS_LEAF_TO_NODE:
> + goto das_node;
> + default:
> + break;
> + }
> +
> + /*
> + * 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->namelen, 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 already in leaf format, jump straight to
> @@ -292,40 +362,53 @@ xfs_attr_set_args(
> if (xfs_attr_is_shortform(dp)) {
>
> /*
> - * If the attr was successfully set in shortform, the
> - * transaction is committed and set to NULL. Otherwise, is it
> - * converted from shortform to leaf, and the transaction is
> - * retained.
> + * If the attr was successfully set in shortform, no need to
> + * continue. Otherwise, is it converted from shortform to leaf
> + * and -EAGAIN is returned.
> */
> - error = xfs_attr_set_shortform(args, &leaf_bp);
> - if (error || !args->trans)
> - return error;
> + error = xfs_attr_set_shortform(args, leaf_bp);
> + if (error == -EAGAIN) {
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> + dac->dela_state = XFS_DAS_ADD_LEAF;
> + }
> + return error;
> }
>
> - if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> - error = xfs_attr_leaf_addname(args);
> - if (error != -ENOSPC)
> - return error;
> +das_add_leaf:
>
> - /*
> - * Commit that transaction so that the node_addname()
> - * call can manage its own transactions.
> - */
> - error = xfs_defer_finish(&args->trans);
> - if (error)
> - return error;
> + /*
> + * 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;
> + }
>
> - /*
> - * Commit the current trans (including the inode) and
> - * start a new one.
> - */
> - error = xfs_trans_roll_inode(&args->trans, dp);
> - if (error)
> + if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> + error = xfs_attr_leaf_try_add(args, *leaf_bp);
> + switch (error) {
> + case -ENOSPC:
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> + dac->dela_state = XFS_DAS_LEAF_TO_NODE;
> + return -EAGAIN;
> + case 0:
> + dac->dela_state = XFS_DAS_FOUND_LBLK;
> + return -EAGAIN;
> + default:
> return error;
> -
> + }
> +das_leaf:
> + error = xfs_attr_leaf_addname(dac);
> + if (error == -ENOSPC) {
> + dac->dela_state = XFS_DAS_LEAF_TO_NODE;
> + return -EAGAIN;
> + }
> + return error;
> }
> -
> - error = xfs_attr_node_addname(args);
> +das_node:
> + error = xfs_attr_node_addname(dac);
> return error;
> }
>
> @@ -716,28 +799,32 @@ xfs_attr_leaf_try_add(
> *
> * 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
> + * -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_leaf_addname(
> - struct xfs_da_args *args)
> + struct xfs_delattr_context *dac)
> {
> - int error, forkoff;
> - struct xfs_buf *bp = NULL;
> - struct xfs_inode *dp = args->dp;
> -
> - trace_xfs_attr_leaf_addname(args);
> -
> - error = xfs_attr_leaf_try_add(args, bp);
> - if (error)
> - return error;
> + struct xfs_da_args *args = dac->da_args;
> + struct xfs_buf *bp = NULL;
> + int error, forkoff;
> + struct xfs_inode *dp = args->dp;
>
> - /*
> - * 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;
> + /* State machine switch */
> + switch (dac->dela_state) {
> + case XFS_DAS_FLIP_LFLAG:
> + goto das_flip_flag;
> + case XFS_DAS_ALLOC_LEAF:
> + goto das_alloc_leaf;
> + case XFS_DAS_RM_LBLK:
> + goto das_rm_lblk;
> + default:
> + break;
> + }
>
> /*
> * If there was an out-of-line value, allocate the blocks we
> @@ -746,7 +833,28 @@ xfs_attr_leaf_addname(
> * 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 */
> + error = xfs_attr_rmtval_set_init(dac);
> + if (error)
> + return error;
> +
> + /*
> + * Roll through the "value", allocating blocks on disk as
> + * required.
> + */
> +das_alloc_leaf:
> + while (dac->blkcnt > 0) {
> + error = xfs_attr_rmtval_set_blk(dac);
> + if (error)
> + return error;
> +
> + dac->flags |= XFS_DAC_DEFER_FINISH;
> + dac->dela_state = XFS_DAS_ALLOC_LEAF;
> + return -EAGAIN;
> + }
> +
> + error = xfs_attr_rmtval_set_value(args);
> if (error)
> return error;
> }
> @@ -765,22 +873,25 @@ xfs_attr_leaf_addname(
> error = xfs_attr3_leaf_flipflags(args);
> if (error)
> return error;
> - /*
> - * 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;
> +das_flip_flag:
> /*
> * Dismantle the "old" attribute/value pair by removing
> * a "remote" value (if it exists).
> */
> xfs_attr_restore_rmt_blk(args);
>
> + xfs_attr_rmtval_invalidate(args);
> +das_rm_lblk:
> if (args->rmtblkno) {
> - error = xfs_attr_rmtval_remove(args);
> + error = __xfs_attr_rmtval_remove(args);
> +
> + if (error == -EAGAIN) {
> + dac->dela_state = XFS_DAS_RM_LBLK;
Similar to what I had observed in the patch "Add delay ready attr remove
routines",
Shouldn't XFS_DAC_DEFER_FINISH be set in dac->flags?
__xfs_attr_rmtval_remove() calls __xfs_bunmapi() which would
have added items to the deferred list.
--
chandan
