On Tuesday 27 October 2020 9:02:05 PM IST Allison Henderson wrote:
>
> On 10/27/20 2:59 AM, Chandan Babu R wrote:
> > On Friday 23 October 2020 12:04:27 PM IST 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 | 200 +++++++++++++++++++++++++++++-----------
> >> fs/xfs/libxfs/xfs_attr.h | 72 +++++++++++++++
> >> fs/xfs/libxfs/xfs_attr_leaf.c | 2 +-
> >> fs/xfs/libxfs/xfs_attr_remote.c | 37 ++++----
> >> fs/xfs/libxfs/xfs_attr_remote.h | 2 +-
> >> fs/xfs/xfs_attr_inactive.c | 2 +-
> >> 6 files changed, 241 insertions(+), 74 deletions(-)
> >>
> >> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> >> index f4d39bf..6ca94cb 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 +264,33 @@ 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 = 0;
> >> +
> >> + 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;
> >> + }
> >> +
> >> + return xfs_trans_roll_inode(&args->trans, args->dp);
> >> +}
> >> +
> >> +/*
> >> * Set the attribute specified in @args.
> >> */
> >> int
> >> @@ -364,23 +391,54 @@ 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 = 0;
> >
> > I guess the explicit initialization of "error" can be removed since the
> > value returned by the call to xfs_attr_remove_iter() will overwrite it.
> Sure, will fix
> >
> >> + 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;
> >> +}
> >> +
> >> +/*
> >> + * 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 (dac->dela_state == XFS_DAS_RM_SHRINK)
> >> + goto node;
> >>
> >> if (!xfs_inode_hasattr(dp)) {
> >> - error = -ENOATTR;
> >> + return -ENOATTR;
> >> } else if (dp->i_afp->if_format == XFS_DINODE_FMT_LOCAL) {
> >> ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> >> - error = xfs_attr_shortform_remove(args);
> >> + return 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_leaf_removename(args);
> >> }
> >> -
> >> - return error;
> >> +node:
> >> + return xfs_attr_node_removename_iter(dac);
> >> }
> >>
> >> /*
> >> @@ -1178,10 +1236,11 @@ 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,
> >> + struct xfs_da_state **state)
> >> {
> >> - int error;
> >> + struct xfs_da_args *args = dac->da_args;
> >> + int error;
> >>
> >> error = xfs_attr_node_hasname(args, state);
> >> if (error != -EEXIST)
> >> @@ -1191,6 +1250,12 @@ int xfs_attr_node_removename_setup(
> >> ASSERT((*state)->path.blk[(*state)->path.active - 1].magic ==
> >> XFS_ATTR_LEAF_MAGIC);
> >>
> >> + /*
> >> + * Store state in the context incase we need to cycle out the
> >> + * transaction
> >> + */
> >> + dac->da_state = *state;
> >> +
> >> if (args->rmtblkno > 0) {
> >> error = xfs_attr_leaf_mark_incomplete(args, *state);
> >> if (error)
> >> @@ -1203,13 +1268,16 @@ 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;
> >>
> >> @@ -1221,21 +1289,27 @@ xfs_attr_node_remove_rmt(
> >> }
> >>
> >> /*
> >> - * 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)
> >> {
> >> - struct xfs_da_state_blk *blk;
> >> - int retval, error;
> >> - struct xfs_inode *dp = args->dp;
> >> + struct xfs_da_args *args = dac->da_args;
> >> + struct xfs_da_state *state;
> >> + struct xfs_da_state_blk *blk;
> >> + int retval, error = 0;
> >>
> >> + state = dac->da_state;
> >>
> >> /*
> >> * If there is an out-of-line value, de-allocate the blocks.
> >> @@ -1243,7 +1317,10 @@ xfs_attr_node_remove_step(
> >> * 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;
> >> }
> >> @@ -1257,21 +1334,18 @@ xfs_attr_node_remove_step(
> >> xfs_da3_fixhashpath(state, &state->path);
> >>
> >> /*
> >> - * Check to see if the tree needs to be collapsed.
> >> + * Check to see if the tree needs to be collapsed. Set the flag to
> >> + * indicate that the calling function needs to move the to shrink
> >> + * operation
> >> */
> >> 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.
> >> - */
> >> - error = xfs_trans_roll_inode(&args->trans, dp);
> >> - if (error)
> >> - return error;
> >> +
> >> + dac->flags |= XFS_DAC_DEFER_FINISH;
> >> + dac->dela_state = XFS_DAS_RM_SHRINK;
> >> + return -EAGAIN;
> >> }
> >>
> >> return error;
> >> @@ -1282,31 +1356,53 @@ xfs_attr_node_remove_step(
> >> *
> >> * This routine will find the blocks of the name to remove, remove them and
> >> * shirnk 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;
> >> - int error;
> >> - struct xfs_inode *dp = args->dp;
> >> + struct xfs_da_args *args = dac->da_args;
> >> + struct xfs_da_state *state;
> >> + int error;
> >> + struct xfs_inode *dp = args->dp;
> >>
> >> trace_xfs_attr_node_removename(args);
> >> + state = dac->da_state;
> >>
> >> - error = xfs_attr_node_removename_setup(args, &state);
> >> - if (error)
> >> - goto out;
> >> + if ((dac->flags & XFS_DAC_NODE_RMVNAME_INIT) == 0) {
> >> + dac->flags |= XFS_DAC_NODE_RMVNAME_INIT;
> >> + error = xfs_attr_node_removename_setup(dac, &state);
> >> + if (error)
> >> + goto out;
> >> + }
> >>
> >> - error = xfs_attr_node_remove_step(args, state);
> >> - if (error)
> >> - goto out;
> >> + switch (dac->dela_state) {
> >> + case XFS_DAS_UNINIT:
> >> + error = xfs_attr_node_remove_step(dac);
> >> + if (error)
> >> + break;
> >>
> >> - /*
> >> - * 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);
> >> + /* do not break, proceed to shrink if needed */
> >> + 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);
> >> + return -EINVAL;
> >
> > I don't think it is possible in a real world scenario, but if "state" were
> > pointing to allocated memory then the above return value might leak the
> > corresponding memory.
> Hmm, trying to follow you here.... I'm assuming you meant dela_state
> instead of state since that's what controls the switch. The dac
> structure is zeroed when allocated to avoid this. Most of the time when
> this switch executes, dela_state is zero. I did have to add the
> XFS_DAS_UNINIT from the previous suggestion in the last revision though
> or it generates warnings.
> >
Sorry, I should have clarified that I was referring to the allocated
memory pointed to by dac->da_state. If dac->da_state was pointing to a valid
memory location and dac->dela_state's value is not equal to either
XFS_DAS_UNINIT nor XFS_DAS_RM_SHRINK then the code under the "default" clause
will execute causing -EINVAL to be returned. This could leak the memory
pointed to by dac->da_state.
> > Apart from the above nit, the remaining changes look good to me.
> Ok, thanks for the review!
> Allison
>
> >
> > Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> >
> >> + }
> >> +
> >> + 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..64dcf0f 100644
> >> --- a/fs/xfs/libxfs/xfs_attr.h
> >> +++ b/fs/xfs/libxfs/xfs_attr.h
> >> @@ -74,6 +74,74 @@ 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()
> >> + * XFS_DAS_RM_SHRINK ─┐
> >> + * (subroutine state) │
> >> + * └─>xfs_attr_node_removename()
> >> + * │
> >> + * v
> >> + * need to
> >> + * shrink tree? ─n─┐
> >> + * │ │
> >> + * y │
> >> + * │ │
> >> + * v │
> >> + * XFS_DAS_RM_SHRINK │
> >> + * │ │
> >> + * 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 */
> >> +#define XFS_DAC_NODE_RMVNAME_INIT 0x02 /* xfs_attr_node_removename init */
> >> +
> >> +/*
> >> + * 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 +159,10 @@ 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 bb128db..338377e 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..1426c15 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);
> >>
> >> @@ -685,19 +687,17 @@ 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);
> >>
> >> - return 0;
> >> + } while (true);
> >> +
> >> + return error;
> >> }
> >>
> >> /*
> >> @@ -707,9 +707,10 @@ xfs_attr_rmtval_remove(
> >> */
> >> 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 +720,10 @@ __xfs_attr_rmtval_remove(
> >> if (error)
> >> return error;
> >>
> >> - error = xfs_defer_finish(&args->trans);
> >> - if (error)
> >> - return error;
> >> -
> >> - if (!done)
> >> + 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
