[PATCH 1/5] xfs: clean up inode locking for RENAME_WHITEOUT

Dave Chinner
2015-03-24T10:59:42Z

From: Dave Chinner <dchinner@redhat.com>

When doing RENAME_WHITEOUT, we now have to lock 5 inodes into the
rename transaction. This means we need to update
xfs_sort_for_rename() and xfs_lock_inodes() to handle up to 5
inodes. Because of the vagaries of rename, this means we could have
anywhere between 3 and 5 inodes locked into the transaction....

While xfs_lock_inodes() does not need anything other than an assert
telling us we are passing more inodes that we ever thought we should
see, it could do with a logic rework to remove all the indenting.
This is not a functional change - it just makes the code a lot
easier to read.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_inode.c | 145 +++++++++++++++++++++++++----------------------------
1 file changed, 67 insertions(+), 78 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 5a44f1c..e38bc40 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -391,15 +391,14 @@ xfs_lock_inumorder(int lock_mode, int subclass)
}

/*
- * The following routine will lock n inodes in exclusive mode.
- * We assume the caller calls us with the inodes in i_ino order.
+ * The following routine will lock n inodes in exclusive mode. We assume the
+ * caller calls us with the inodes in i_ino order.
*
- * We need to detect deadlock where an inode that we lock
- * is in the AIL and we start waiting for another inode that is locked
- * by a thread in a long running transaction (such as truncate). This can
- * result in deadlock since the long running trans might need to wait
- * for the inode we just locked in order to push the tail and free space
- * in the log.
+ * We need to detect deadlock where an inode that we lock is in the AIL and we
+ * start waiting for another inode that is locked by a thread in a long running
+ * transaction (such as truncate). This can result in deadlock since the long
+ * running trans might need to wait for the inode we just locked in order to
+ * push the tail and free space in the log.
*/
void
xfs_lock_inodes(
@@ -410,30 +409,27 @@ xfs_lock_inodes(
int attempts = 0, i, j, try_lock;
xfs_log_item_t *lp;

- ASSERT(ips && (inodes >= 2)); /* we need at least two */
+ /* currently supports between 2 and 5 inodes */
+ ASSERT(ips && inodes >= 2 && inodes <= 5);

try_lock = 0;
i = 0;
-
again:
for (; i < inodes; i++) {
ASSERT(ips[i]);

- if (i && (ips[i] == ips[i-1])) /* Already locked */
+ if (i && (ips[i] == ips[i - 1])) /* Already locked */
continue;

/*
- * If try_lock is not set yet, make sure all locked inodes
- * are not in the AIL.
- * If any are, set try_lock to be used later.
+ * If try_lock is not set yet, make sure all locked inodes are
+ * not in the AIL. If any are, set try_lock to be used later.
*/
-
if (!try_lock) {
for (j = (i - 1); j >= 0 && !try_lock; j--) {
lp = (xfs_log_item_t *)ips[j]->i_itemp;
- if (lp && (lp->li_flags & XFS_LI_IN_AIL)) {
+ if (lp && (lp->li_flags & XFS_LI_IN_AIL))
try_lock++;
- }
}
}

@@ -443,51 +439,42 @@ again:
* we can't get any, we must release all we have
* and try again.
*/
+ if (!try_lock) {
+ xfs_ilock(ips[i], xfs_lock_inumorder(lock_mode, i));
+ continue;
+ }
+
+ /* try_lock means we have an inode locked that is in the AIL. */
+ ASSERT(i != 0);
+ if (xfs_ilock_nowait(ips[i], xfs_lock_inumorder(lock_mode, i)))
+ continue;

- if (try_lock) {
- /* try_lock must be 0 if i is 0. */
+ /*
+ * Unlock all previous guys and try again. xfs_iunlock will try
+ * to push the tail if the inode is in the AIL.
+ */
+ attempts++;
+ for (j = i - 1; j >= 0; j--) {
/*
- * try_lock means we have an inode locked
- * that is in the AIL.
+ * Check to see if we've already unlocked this one. Not
+ * the first one going back, and the inode ptr is the
+ * same.
*/
- ASSERT(i != 0);
- if (!xfs_ilock_nowait(ips[i], xfs_lock_inumorder(lock_mode, i))) {
- attempts++;
-
- /*
- * Unlock all previous guys and try again.
- * xfs_iunlock will try to push the tail
- * if the inode is in the AIL.
- */
-
- for(j = i - 1; j >= 0; j--) {
-
- /*
- * Check to see if we've already
- * unlocked this one.
- * Not the first one going back,
- * and the inode ptr is the same.
- */
- if ((j != (i - 1)) && ips[j] ==
- ips[j+1])
- continue;
-
- xfs_iunlock(ips[j], lock_mode);
- }
+ if (j != (i - 1) && ips[j] == ips[j + 1])
+ continue;
+
+ xfs_iunlock(ips[j], lock_mode);
+ }

- if ((attempts % 5) == 0) {
- delay(1); /* Don't just spin the CPU */
+ if ((attempts % 5) == 0) {
+ delay(1); /* Don't just spin the CPU */
#ifdef DEBUG
- xfs_lock_delays++;
+ xfs_lock_delays++;
#endif
- }
- i = 0;
- try_lock = 0;
- goto again;
- }
- } else {
- xfs_ilock(ips[i], xfs_lock_inumorder(lock_mode, i));
}
+ i = 0;
+ try_lock = 0;
+ goto again;
}

#ifdef DEBUG
@@ -2681,19 +2668,22 @@ xfs_remove(
/*
* Enter all inodes for a rename transaction into a sorted array.
*/
+#define __XFS_SORT_INODES 5
STATIC void
xfs_sort_for_rename(
- xfs_inode_t *dp1, /* in: old (source) directory inode */
- xfs_inode_t *dp2, /* in: new (target) directory inode */
- xfs_inode_t *ip1, /* in: inode of old entry */
- xfs_inode_t *ip2, /* in: inode of new entry, if it
- already exists, NULL otherwise. */
- xfs_inode_t **i_tab,/* out: array of inode returned, sorted */
- int *num_inodes) /* out: number of inodes in array */
+ struct xfs_inode *dp1, /* in: old (source) directory inode */
+ struct xfs_inode *dp2, /* in: new (target) directory inode */
+ struct xfs_inode *ip1, /* in: inode of old entry */
+ struct xfs_inode *ip2, /* in: inode of new entry */
+ struct xfs_inode *wino, /* in: whiteout inode */
+ struct xfs_inode **i_tab,/* out: sorted array of inodes */
+ int *num_inodes) /* in/out: inodes in array */
{
- xfs_inode_t *temp;
int i, j;

+ ASSERT(*num_inodes == __XFS_SORT_INODES);
+ memset(i_tab, 0, *num_inodes * sizeof(struct xfs_inode *));
+
/*
* i_tab contains a list of pointers to inodes. We initialize
* the table here & we'll sort it. We will then use it to
@@ -2701,25 +2691,24 @@ xfs_sort_for_rename(
*
* Note that the table may contain duplicates. e.g., dp1 == dp2.
*/
- i_tab[0] = dp1;
- i_tab[1] = dp2;
- i_tab[2] = ip1;
- if (ip2) {
- *num_inodes = 4;
- i_tab[3] = ip2;
- } else {
- *num_inodes = 3;
- i_tab[3] = NULL;
- }
+ i = 0;
+ i_tab[i++] = dp1;
+ i_tab[i++] = dp2;
+ i_tab[i++] = ip1;
+ if (ip2)
+ i_tab[i++] = ip2;
+ if (wino)
+ i_tab[i++] = wino;
+ *num_inodes = i;

/*
* Sort the elements via bubble sort. (Remember, there are at
- * most 4 elements to sort, so this is adequate.)
+ * most 5 elements to sort, so this is adequate.)
*/
for (i = 0; i < *num_inodes; i++) {
for (j = 1; j < *num_inodes; j++) {
if (i_tab[j]->i_ino < i_tab[j-1]->i_ino) {
- temp = i_tab[j];
+ struct xfs_inode *temp = i_tab[j];
i_tab[j] = i_tab[j-1];
i_tab[j-1] = temp;
}
@@ -2867,16 +2856,16 @@ xfs_rename(
xfs_fsblock_t first_block;
int cancel_flags;
int committed;
- xfs_inode_t *inodes[4];
+ xfs_inode_t *inodes[__XFS_SORT_INODES];
+ int num_inodes = __XFS_SORT_INODES;
int spaceres;
- int num_inodes;

trace_xfs_rename(src_dp, target_dp, src_name, target_name);

new_parent = (src_dp != target_dp);
src_is_directory = S_ISDIR(src_ip->i_d.di_mode);

- xfs_sort_for_rename(src_dp, target_dp, src_ip, target_ip,
+ xfs_sort_for_rename(src_dp, target_dp, src_ip, target_ip, NULL,
inodes, &num_inodes);

xfs_bmap_init(&free_list, &first_block);
--
2.0.0