Re: [PATCH v4 17/17] xfs: Add delay ready attr set routines

Allison Collins
2019-11-13T04:59:04Z

On 11/12/19 6:37 AM, Brian Foster wrote:
> On Wed, Nov 06, 2019 at 06:28:01PM -0700, 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_later, which uses a state machine to keep track
>> of where it was when EAGAIN was returned. Part of
>> xfs_attr_leaf_addname has been factored out into a new helper
>> function xfs_attr_leaf_try_add to allow transaction cycling between
>> the two routines, and the flipflags logic has been removed since we
>> can simply cancel the transaction upon error. xfs_attr_set_args
>> consists of a simple loop to refresh the transaction until the
>> operation is completed.
>>
>> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
>> ---
>
> Pretty much the same fundamental comments here as for the remove patch.
> Can we break things down further to avoid much of the jumping into if
> branch behavior and such? I also wonder if it might be possible to split
> this one up into smaller patches to fix up the leaf/node paths
> separately, but additional prep refactoring might simplify things enough
> on its own to make that unnecessary..
>
> Brian

Sure, I'll see if I can get the branching out of the if statements.
Maybe I can break this up into smaller patches too. Thanks again for
the reviews!

Allison

>
>> fs/xfs/libxfs/xfs_attr.c | 435 +++++++++++++++++++++++------------------------
>> fs/xfs/libxfs/xfs_attr.h | 1 +
>> 2 files changed, 211 insertions(+), 225 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
>> index 38d5c5c..97e5ae0 100644
>> --- a/fs/xfs/libxfs/xfs_attr.c
>> +++ b/fs/xfs/libxfs/xfs_attr.c
>> @@ -58,6 +58,7 @@ 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 int
>> @@ -250,9 +251,79 @@ int
>> xfs_attr_set_args(
>> struct xfs_da_args *args)
>> {
>> + int error = 0;
>> + int err2 = 0;
>> + struct xfs_buf *leaf_bp = NULL;
>> +
>> + do {
>> + error = xfs_attr_set_later(args, &leaf_bp);
>> + if (error && error != -EAGAIN)
>> + goto out;
>> +
>> + xfs_trans_log_inode(args->trans, args->dp,
>> + XFS_ILOG_CORE | XFS_ILOG_ADATA);
>> +
>> + err2 = xfs_trans_roll(&args->trans);
>> + if (err2) {
>> + error = err2;
>> + goto out;
>> + }
>> +
>> + /* Rejoin inode and leaf if needed */
>> + xfs_trans_ijoin(args->trans, args->dp, 0);
>> + if (leaf_bp) {
>> + xfs_trans_bjoin(args->trans, leaf_bp);
>> + xfs_trans_bhold(args->trans, leaf_bp);
>> + }
>> +
>> + } while (error == -EAGAIN);
>> +
>> +out:
>> + 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_later(
>> + struct xfs_da_args *args,
>> + struct xfs_buf **leaf_bp)
>> +{
>> struct xfs_inode *dp = args->dp;
>> - struct xfs_buf *leaf_bp = NULL;
>> - int error, error2 = 0;;
>> + int error = 0;
>> + int sf_size;
>> +
>> + /* State machine switch */
>> + switch (args->dc.dc_state) {
>> + case XFS_DC_SF_TO_LEAF:
>> + goto sf_to_leaf;
>> + case XFS_DC_ALLOC_LEAF:
>> + case XFS_DC_FOUND_LBLK:
>> + goto leaf;
>> + case XFS_DC_FOUND_NBLK:
>> + case XFS_DC_ALLOC_NODE:
>> + case XFS_DC_LEAF_TO_NODE:
>> + goto 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->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,
>> @@ -272,21 +343,14 @@ xfs_attr_set_args(
>> * Try to add the attr to the attribute list in the inode.
>> */
>> error = xfs_attr_try_sf_addname(dp, args);
>> - if (error != -ENOSPC) {
>> - if (dp->i_mount->m_flags & XFS_MOUNT_WSYNC)
>> - xfs_trans_set_sync(args->trans);
>> -
>> - error2 = xfs_trans_commit(args->trans);
>> - args->trans = NULL;
>> - return error ? error : error2;
>> - }
>> -
>> + 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);
>> + error = xfs_attr_shortform_to_leaf(args, leaf_bp);
>> if (error)
>> return error;
>>
>> @@ -294,43 +358,42 @@ xfs_attr_set_args(
>> * 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.
>> */
>> - 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;
>> - }
>> +
>> + xfs_trans_bhold(args->trans, *leaf_bp);
>> + args->dc.dc_state = XFS_DC_SF_TO_LEAF;
>> + return -EAGAIN;
>> + }
>> +sf_to_leaf:
>> +
>> + /*
>> + * 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 (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
>> + error = xfs_attr_leaf_try_add(args, *leaf_bp);
>> + if (error == -ENOSPC)
>> + args->dc.dc_state = XFS_DC_LEAF_TO_NODE;
>> + else if (error)
>> + return error;
>> + else
>> + args->dc.dc_state = XFS_DC_FOUND_LBLK;
>> + return -EAGAIN;
>> +leaf:
>> error = xfs_attr_leaf_addname(args);
>> if (error == -ENOSPC) {
>> - /*
>> - * Commit that transaction so that the node_addname()
>> - * call can manage its own transactions.
>> - */
>> - error = xfs_defer_finish(&args->trans);
>> - if (error)
>> - return error;
>> -
>> - /*
>> - * Commit the current trans (including the inode) and
>> - * start a new one.
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, dp);
>> - if (error)
>> - return error;
>> -
>> - /*
>> - * Fob the rest of the problem off on the Btree code.
>> - */
>> - error = xfs_attr_node_addname(args);
>> + args->dc.dc_state = XFS_DC_LEAF_TO_NODE;
>> + return -EAGAIN;
>> }
>> } else {
>> + args->dc.dc_state = XFS_DC_LEAF_TO_NODE;
>> +node:
>> error = xfs_attr_node_addname(args);
>> }
>> return error;
>> @@ -764,27 +827,26 @@ 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)
>> {
>> - int error, forkoff;
>> - struct xfs_buf *bp = NULL;
>> + int error, nmap;
>> struct xfs_inode *dp = args->dp;
>> + struct xfs_bmbt_irec *map = &args->dc.map;
>>
>> - trace_xfs_attr_leaf_addname(args);
>> -
>> - error = xfs_attr_leaf_try_add(args, bp);
>> - if (error)
>> - return error;
>> -
>> - /*
>> - * 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 (args->dc.dc_state) {
>> + case XFS_DC_ALLOC_LEAF:
>> + goto alloc_leaf;
>> + default:
>> + break;
>> + }
>>
>> /*
>> * If there was an out-of-line value, allocate the blocks we
>> @@ -793,90 +855,58 @@ xfs_attr_leaf_addname(struct xfs_da_args *args)
>> * maximum size of a transaction and/or hit a deadlock.
>> */
>> if (args->rmtblkno > 0) {
>> - error = xfs_attr_rmtval_set(args);
>> - if (error)
>> - return error;
>> - }
>>
>> - /*
>> - * If this is an atomic rename operation, we must "flip" the
>> - * incomplete flags on the "new" and "old" attribute/value pairs
>> - * so that one disappears and one appears atomically. Then we
>> - * must remove the "old" attribute/value pair.
>> - */
>> - if (args->op_flags & XFS_DA_OP_RENAME) {
>> - /*
>> - * In a separate transaction, set the incomplete flag on the
>> - * "old" attr and clear the incomplete flag on the "new" attr.
>> - */
>> - 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;
>> + /* Open coded xfs_attr_rmtval_set without trans handling */
>>
>> - /*
>> - * Dismantle the "old" attribute/value pair by removing
>> - * a "remote" value (if it exists).
>> - */
>> - args->index = args->index2;
>> - args->blkno = args->blkno2;
>> - args->rmtblkno = args->rmtblkno2;
>> - args->rmtblkcnt = args->rmtblkcnt2;
>> - args->rmtvaluelen = args->rmtvaluelen2;
>> - if (args->rmtblkno) {
>> - error = xfs_attr_rmtval_remove(args);
>> - if (error)
>> - return error;
>> - }
>> + 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));
>>
>> - /*
>> - * Read in the block containing the "old" attr, then
>> - * remove the "old" attr from that block (neat, huh!)
>> - */
>> - error = xfs_attr3_leaf_read(args->trans, args->dp, args->blkno,
>> - XFS_DABUF_MAP_NOMAPPING, &bp);
>> + error = xfs_attr_rmt_find_hole(args);
>> if (error)
>> return error;
>>
>> - xfs_attr3_leaf_remove(bp, args);
>> + args->dc.blkcnt = args->rmtblkcnt;
>> + args->dc.lblkno = args->rmtblkno;
>>
>> /*
>> - * If the result is small enough, shrink it all into the inode.
>> + * Roll through the "value", allocating blocks on disk as
>> + * required.
>> */
>> - if ((forkoff = xfs_attr_shortform_allfit(bp, dp))) {
>> - error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
>> - /* bp is gone due to xfs_da_shrink_inode */
>> - if (error)
>> - return error;
>> - error = xfs_defer_finish(&args->trans);
>> +alloc_leaf:
>> + 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));
>>
>> - /*
>> - * Commit the remove and start the next trans in series.
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, dp);
>> + /* roll attribute extent map forwards */
>> + args->dc.lblkno += map->br_blockcount;
>> + args->dc.blkcnt -= map->br_blockcount;
>>
>> - } else if (args->rmtblkno > 0) {
>> - /*
>> - * Added a "remote" value, just clear the incomplete flag.
>> - */
>> - error = xfs_attr3_leaf_clearflag(args);
>> + args->dc.dc_state = XFS_DC_ALLOC_LEAF;
>> + return -EAGAIN;
>> + }
>> +
>> + error = xfs_attr_rmtval_set_value(args);
>> if (error)
>> return error;
>> + }
>>
>> + if (args->rmtblkno > 0) {
>> /*
>> - * Commit the flag value change and start the next trans in
>> - * series.
>> + * Added a "remote" value, just clear the incomplete flag.
>> */
>> - error = xfs_trans_roll_inode(&args->trans, args->dp);
>> + error = xfs_attr3_leaf_clearflag(args);
>> }
>> return error;
>> }
>> @@ -1017,16 +1047,23 @@ xfs_attr_node_hasname(
>> *
>> * "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
>> + * -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_addname(
>> struct xfs_da_args *args)
>> {
>> - struct xfs_da_state *state;
>> + struct xfs_da_state *state = NULL;
>> struct xfs_da_state_blk *blk;
>> struct xfs_inode *dp;
>> - struct xfs_mount *mp;
>> - int retval, error;
>> + int retval = 0;
>> + int error = 0;
>> + int nmap;
>> + struct xfs_bmbt_irec *map = &args->dc.map;
>>
>> trace_xfs_attr_node_addname(args);
>>
>> @@ -1034,8 +1071,17 @@ xfs_attr_node_addname(
>> * Fill in bucket of arguments/results/context to carry around.
>> */
>> dp = args->dp;
>> - mp = dp->i_mount;
>> -restart:
>> +
>> + /* State machine switch */
>> + switch (args->dc.dc_state) {
>> + case XFS_DC_FOUND_NBLK:
>> + goto found_nblk;
>> + case XFS_DC_ALLOC_NODE:
>> + goto alloc_node;
>> + default:
>> + break;
>> + }
>> +
>> /*
>> * Search to see if name already exists, and get back a pointer
>> * to where it should go.
>> @@ -1085,19 +1131,12 @@ xfs_attr_node_addname(
>> error = xfs_attr3_leaf_to_node(args);
>> if (error)
>> goto out;
>> - error = xfs_defer_finish(&args->trans);
>> - if (error)
>> - goto out;
>>
>> /*
>> - * Commit the node conversion and start the next
>> - * trans in the chain.
>> + * Restart routine from the top. No need to set the
>> + * state
>> */
>> - error = xfs_trans_roll_inode(&args->trans, dp);
>> - if (error)
>> - goto out;
>> -
>> - goto restart;
>> + return -EAGAIN;
>> }
>>
>> /*
>> @@ -1109,9 +1148,6 @@ xfs_attr_node_addname(
>> error = xfs_da3_split(state);
>> if (error)
>> goto out;
>> - error = xfs_defer_finish(&args->trans);
>> - if (error)
>> - goto out;
>> } else {
>> /*
>> * Addition succeeded, update Btree hashvals.
>> @@ -1126,13 +1162,9 @@ xfs_attr_node_addname(
>> xfs_da_state_free(state);
>> state = NULL;
>>
>> - /*
>> - * Commit the leaf addition or btree split and start the next
>> - * trans in the chain.
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, dp);
>> - if (error)
>> - goto out;
>> + args->dc.dc_state = XFS_DC_FOUND_NBLK;
>> + return -EAGAIN;
>> +found_nblk:
>>
>> /*
>> * If there was an out-of-line value, allocate the blocks we
>> @@ -1141,104 +1173,57 @@ xfs_attr_node_addname(
>> * maximum size of a transaction and/or hit a deadlock.
>> */
>> if (args->rmtblkno > 0) {
>> - error = xfs_attr_rmtval_set(args);
>> - if (error)
>> - return error;
>> - }
>> + /* Open coded xfs_attr_rmtval_set without trans handling */
>> + 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));
>>
>> - /*
>> - * If this is an atomic rename operation, we must "flip" the
>> - * incomplete flags on the "new" and "old" attribute/value pairs
>> - * so that one disappears and one appears atomically. Then we
>> - * must remove the "old" attribute/value pair.
>> - */
>> - if (args->op_flags & XFS_DA_OP_RENAME) {
>> - /*
>> - * In a separate transaction, set the incomplete flag on the
>> - * "old" attr and clear the incomplete flag on the "new" attr.
>> - */
>> - error = xfs_attr3_leaf_flipflags(args);
>> - if (error)
>> - goto out;
>> - /*
>> - * Commit the flag value change and start the next trans in
>> - * series
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, args->dp);
>> + error = xfs_attr_rmt_find_hole(args);
>> if (error)
>> - goto out;
>> + return error;
>>
>> + args->dc.blkcnt = args->rmtblkcnt;
>> + args->dc.lblkno = args->rmtblkno;
>> /*
>> - * Dismantle the "old" attribute/value pair by removing
>> - * a "remote" value (if it exists).
>> + * Roll through the "value", allocating blocks on disk as
>> + * required.
>> */
>> - args->index = args->index2;
>> - args->blkno = args->blkno2;
>> - args->rmtblkno = args->rmtblkno2;
>> - args->rmtblkcnt = args->rmtblkcnt2;
>> - args->rmtvaluelen = args->rmtvaluelen2;
>> - if (args->rmtblkno) {
>> - error = xfs_attr_rmtval_remove(args);
>> +alloc_node:
>> + 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;
>> - }
>>
>> - /*
>> - * Re-find the "old" attribute entry after any split ops.
>> - * The INCOMPLETE flag means that we will find the "old"
>> - * attr, not the "new" one.
>> - */
>> - args->name.type |= XFS_ATTR_INCOMPLETE;
>> - state = xfs_da_state_alloc();
>> - state->args = args;
>> - state->mp = mp;
>> - state->inleaf = 0;
>> - error = xfs_da3_node_lookup_int(state, &retval);
>> - if (error)
>> - goto out;
>> + ASSERT(nmap == 1);
>> + ASSERT((map->br_startblock != DELAYSTARTBLOCK) &&
>> + (map->br_startblock != HOLESTARTBLOCK));
>>
>> - /*
>> - * Remove the name and update the hashvals in the tree.
>> - */
>> - blk = &state->path.blk[ state->path.active-1 ];
>> - ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
>> - error = xfs_attr3_leaf_remove(blk->bp, args);
>> - xfs_da3_fixhashpath(state, &state->path);
>> + /* roll attribute extent map forwards */
>> + args->dc.lblkno += map->br_blockcount;
>> + args->dc.blkcnt -= map->br_blockcount;
>>
>> - /*
>> - * 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;
>> + args->dc.dc_state = XFS_DC_ALLOC_NODE;
>> + return -EAGAIN;
>> }
>>
>> - /*
>> - * Commit and start the next trans in the chain.
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, dp);
>> + error = xfs_attr_rmtval_set_value(args);
>> if (error)
>> - goto out;
>> + return error;
>> + }
>>
>> - } else if (args->rmtblkno > 0) {
>> + if (args->rmtblkno > 0) {
>> /*
>> * Added a "remote" value, just clear the incomplete flag.
>> */
>> error = xfs_attr3_leaf_clearflag(args);
>> if (error)
>> goto out;
>> -
>> - /*
>> - * Commit the flag value change and start the next trans in
>> - * series.
>> - */
>> - error = xfs_trans_roll_inode(&args->trans, args->dp);
>> - if (error)
>> - goto out;
>> }
>> retval = error = 0;
>>
>> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
>> index fb8bf5b..c710387 100644
>> --- a/fs/xfs/libxfs/xfs_attr.h
>> +++ b/fs/xfs/libxfs/xfs_attr.h
>> @@ -149,6 +149,7 @@ 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 flags);
>> 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 flags);
>> int xfs_has_attr(struct xfs_da_args *args);
>> int xfs_attr_remove_args(struct xfs_da_args *args);
>> --
>> 2.7.4
>>
>