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xfs: untangle xfs_dialloc
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Clarify the control flow in xfs_dialloc.  Factor out a helper to go to the
next node from the current one and improve the control flow by expanding
composite if statements and using gotos.

The xfs_ialloc_next_rec helper is borrowed from Dave Chinners dynamic
allocation policy patches.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Alex Elder <[email protected]>
Signed-off-by: Felix Blyakher <[email protected]>
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Christoph Hellwig authored and Felix Blyakher committed Sep 1, 2009
1 parent 0b48db8 commit 4254b0b
Showing 1 changed file with 138 additions and 153 deletions.
291 changes: 138 additions & 153 deletions fs/xfs/xfs_ialloc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -589,6 +589,37 @@ xfs_ialloc_ag_select(
}
}

/*
* Try to retrieve the next record to the left/right from the current one.
*/
STATIC int
xfs_ialloc_next_rec(
struct xfs_btree_cur *cur,
xfs_inobt_rec_incore_t *rec,
int *done,
int left)
{
int error;
int i;

if (left)
error = xfs_btree_decrement(cur, 0, &i);
else
error = xfs_btree_increment(cur, 0, &i);

if (error)
return error;
*done = !i;
if (i) {
error = xfs_inobt_get_rec(cur, rec, &i);
if (error)
return error;
XFS_WANT_CORRUPTED_RETURN(i == 1);
}

return 0;
}


/*
* Visible inode allocation functions.
Expand Down Expand Up @@ -644,8 +675,8 @@ xfs_dialloc(
int j; /* result code */
xfs_mount_t *mp; /* file system mount structure */
int offset; /* index of inode in chunk */
xfs_agino_t pagino; /* parent's a.g. relative inode # */
xfs_agnumber_t pagno; /* parent's allocation group number */
xfs_agino_t pagino; /* parent's AG relative inode # */
xfs_agnumber_t pagno; /* parent's AG number */
xfs_inobt_rec_incore_t rec; /* inode allocation record */
xfs_agnumber_t tagno; /* testing allocation group number */
xfs_btree_cur_t *tcur; /* temp cursor */
Expand Down Expand Up @@ -781,186 +812,140 @@ xfs_dialloc(
goto error0;

/*
* If in the same a.g. as the parent, try to get near the parent.
* If in the same AG as the parent, try to get near the parent.
*/
if (pagno == agno) {
if ((error = xfs_inobt_lookup_le(cur, pagino, 0, 0, &i)))
int doneleft; /* done, to the left */
int doneright; /* done, to the right */

error = xfs_inobt_lookup_le(cur, pagino, 0, 0, &i);
if (error)
goto error0;
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);

error = xfs_inobt_get_rec(cur, &rec, &j);
if (error)
goto error0;
if (i != 0 &&
(error = xfs_inobt_get_rec(cur, &rec, &j)) == 0 &&
j == 1 &&
rec.ir_freecount > 0) {
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);

if (rec.ir_freecount > 0) {
/*
* Found a free inode in the same chunk
* as parent, done.
* as the parent, done.
*/
goto alloc_inode;
}


/*
* In the same a.g. as parent, but parent's chunk is full.
* In the same AG as parent, but parent's chunk is full.
*/
else {
int doneleft; /* done, to the left */
int doneright; /* done, to the right */

if (error)
goto error0;
ASSERT(i == 1);
ASSERT(j == 1);
/*
* Duplicate the cursor, search left & right
* simultaneously.
*/
if ((error = xfs_btree_dup_cursor(cur, &tcur)))
goto error0;
/*
* Search left with tcur, back up 1 record.
*/
if ((error = xfs_btree_decrement(tcur, 0, &i)))
goto error1;
doneleft = !i;
if (!doneleft) {
error = xfs_inobt_get_rec(tcur, &trec, &i);
if (error)
goto error1;
XFS_WANT_CORRUPTED_GOTO(i == 1, error1);
/* duplicate the cursor, search left & right simultaneously */
error = xfs_btree_dup_cursor(cur, &tcur);
if (error)
goto error0;

/* search left with tcur, back up 1 record */
error = xfs_ialloc_next_rec(tcur, &trec, &doneleft, 1);
if (error)
goto error1;

/* search right with cur, go forward 1 record. */
error = xfs_ialloc_next_rec(cur, &rec, &doneright, 0);
if (error)
goto error1;

/*
* Loop until we find an inode chunk with a free inode.
*/
while (!doneleft || !doneright) {
int useleft; /* using left inode chunk this time */

/* figure out the closer block if both are valid. */
if (!doneleft && !doneright) {
useleft = pagino -
(trec.ir_startino + XFS_INODES_PER_CHUNK - 1) <
rec.ir_startino - pagino;
} else {
useleft = !doneleft;
}
/*
* Search right with cur, go forward 1 record.
*/
if ((error = xfs_btree_increment(cur, 0, &i)))
goto error1;
doneright = !i;
if (!doneright) {
error = xfs_inobt_get_rec(cur, &rec, &i);
if (error)
goto error1;
XFS_WANT_CORRUPTED_GOTO(i == 1, error1);

/* free inodes to the left? */
if (useleft && trec.ir_freecount) {
rec = trec;
xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
cur = tcur;
goto alloc_inode;
}
/*
* Loop until we find the closest inode chunk
* with a free one.
*/
while (!doneleft || !doneright) {
int useleft; /* using left inode
chunk this time */

/*
* Figure out which block is closer,
* if both are valid.
*/
if (!doneleft && !doneright)
useleft =
pagino -
(trec.ir_startino +
XFS_INODES_PER_CHUNK - 1) <
rec.ir_startino - pagino;
else
useleft = !doneleft;
/*
* If checking the left, does it have
* free inodes?
*/
if (useleft && trec.ir_freecount) {
/*
* Yes, set it up as the chunk to use.
*/
rec = trec;
xfs_btree_del_cursor(cur,
XFS_BTREE_NOERROR);
cur = tcur;
break;
}
/*
* If checking the right, does it have
* free inodes?
*/
if (!useleft && rec.ir_freecount) {
/*
* Yes, it's already set up.
*/
xfs_btree_del_cursor(tcur,
XFS_BTREE_NOERROR);
break;
}
/*
* If used the left, get another one
* further left.
*/
if (useleft) {
if ((error = xfs_btree_decrement(tcur, 0,
&i)))
goto error1;
doneleft = !i;
if (!doneleft) {
error = xfs_inobt_get_rec(
tcur, &trec, &i);
if (error)
goto error1;
XFS_WANT_CORRUPTED_GOTO(i == 1,
error1);
}
}
/*
* If used the right, get another one
* further right.
*/
else {
if ((error = xfs_btree_increment(cur, 0,
&i)))
goto error1;
doneright = !i;
if (!doneright) {
error = xfs_inobt_get_rec(
cur, &rec, &i);
if (error)
goto error1;
XFS_WANT_CORRUPTED_GOTO(i == 1,
error1);
}
}
/* free inodes to the right? */
if (!useleft && rec.ir_freecount) {
xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
goto alloc_inode;
}
ASSERT(!doneleft || !doneright);

/* get next record to check */
if (useleft) {
error = xfs_ialloc_next_rec(tcur, &trec,
&doneleft, 1);
} else {
error = xfs_ialloc_next_rec(cur, &rec,
&doneright, 0);
}
if (error)
goto error1;
}
ASSERT(!doneleft || !doneright);
}

/*
* In a different a.g. from the parent.
* In a different AG from the parent.
* See if the most recently allocated block has any free.
*/
else if (be32_to_cpu(agi->agi_newino) != NULLAGINO) {
if ((error = xfs_inobt_lookup_eq(cur,
be32_to_cpu(agi->agi_newino), 0, 0, &i)))
error = xfs_inobt_lookup_eq(cur, be32_to_cpu(agi->agi_newino),
0, 0, &i);
if (error)
goto error0;
if (i == 1 &&
(error = xfs_inobt_get_rec(cur, &rec, &j)) == 0 &&
j == 1 &&
rec.ir_freecount > 0) {
/*
* The last chunk allocated in the group still has
* a free inode.
*/

if (i == 1) {
error = xfs_inobt_get_rec(cur, &rec, &j);
if (error)
goto error0;

if (j == 1 && rec.ir_freecount > 0) {
/*
* The last chunk allocated in the group
* still has a free inode.
*/
goto alloc_inode;
}
}

/*
* None left in the last group, search the whole a.g.
* None left in the last group, search the whole AG
*/
else {
error = xfs_inobt_lookup_ge(cur, 0, 0, 0, &i);
if (error)
goto error0;
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);

for (;;) {
error = xfs_inobt_get_rec(cur, &rec, &i);
if (error)
goto error0;
if ((error = xfs_inobt_lookup_ge(cur, 0, 0, 0, &i)))
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
if (rec.ir_freecount > 0)
break;
error = xfs_btree_increment(cur, 0, &i);
if (error)
goto error0;
ASSERT(i == 1);
for (;;) {
error = xfs_inobt_get_rec(cur, &rec, &i);
if (error)
goto error0;
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
if (rec.ir_freecount > 0)
break;
if ((error = xfs_btree_increment(cur, 0, &i)))
goto error0;
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
}
XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
}
}

alloc_inode:
offset = xfs_ialloc_find_free(&rec.ir_free);
ASSERT(offset >= 0);
ASSERT(offset < XFS_INODES_PER_CHUNK);
Expand Down

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