xfs: factor xlog_write
xlog_write is a mess that takes a lot of effort to understand. It is
a mass of nested loops with 4 space indents to get it to fit in 80 columns
and lots of funky variables that aren't obvious what they mean or do.
Break it down into understandable chunks.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 81323d7..4a0ec59 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1630,6 +1630,193 @@
}
/*
+ * Calculate the potential space needed by the log vector. Each region gets
+ * its own xlog_op_header_t and may need to be double word aligned.
+ */
+static int
+xlog_write_calc_vec_length(
+ struct xlog_ticket *ticket,
+ struct xfs_log_iovec reg[],
+ int nentries)
+{
+ int headers = 0;
+ int len = 0;
+ int i;
+
+ /* acct for start rec of xact */
+ if (ticket->t_flags & XLOG_TIC_INITED)
+ headers++;
+
+ for (i = 0; i < nentries; i++) {
+ /* each region gets >= 1 */
+ headers++;
+
+ len += reg[i].i_len;
+ xlog_tic_add_region(ticket, reg[i].i_len, reg[i].i_type);
+ }
+
+ ticket->t_res_num_ophdrs += headers;
+ len += headers * sizeof(struct xlog_op_header);
+
+ return len;
+}
+
+/*
+ * If first write for transaction, insert start record We can't be trying to
+ * commit if we are inited. We can't have any "partial_copy" if we are inited.
+ */
+static int
+xlog_write_start_rec(
+ __psint_t ptr,
+ struct xlog_ticket *ticket)
+{
+ struct xlog_op_header *ophdr = (struct xlog_op_header *)ptr;
+
+ if (!(ticket->t_flags & XLOG_TIC_INITED))
+ return 0;
+
+ ophdr->oh_tid = cpu_to_be32(ticket->t_tid);
+ ophdr->oh_clientid = ticket->t_clientid;
+ ophdr->oh_len = 0;
+ ophdr->oh_flags = XLOG_START_TRANS;
+ ophdr->oh_res2 = 0;
+
+ ticket->t_flags &= ~XLOG_TIC_INITED;
+
+ return sizeof(struct xlog_op_header);
+}
+
+static xlog_op_header_t *
+xlog_write_setup_ophdr(
+ struct log *log,
+ __psint_t ptr,
+ struct xlog_ticket *ticket,
+ uint flags)
+{
+ struct xlog_op_header *ophdr = (struct xlog_op_header *)ptr;
+
+ ophdr->oh_tid = cpu_to_be32(ticket->t_tid);
+ ophdr->oh_clientid = ticket->t_clientid;
+ ophdr->oh_res2 = 0;
+
+ /* are we copying a commit or unmount record? */
+ ophdr->oh_flags = flags;
+
+ /*
+ * We've seen logs corrupted with bad transaction client ids. This
+ * makes sure that XFS doesn't generate them on. Turn this into an EIO
+ * and shut down the filesystem.
+ */
+ switch (ophdr->oh_clientid) {
+ case XFS_TRANSACTION:
+ case XFS_VOLUME:
+ case XFS_LOG:
+ break;
+ default:
+ xfs_fs_cmn_err(CE_WARN, log->l_mp,
+ "Bad XFS transaction clientid 0x%x in ticket 0x%p",
+ ophdr->oh_clientid, ticket);
+ return NULL;
+ }
+
+ return ophdr;
+}
+
+/*
+ * Set up the parameters of the region copy into the log. This has
+ * to handle region write split across multiple log buffers - this
+ * state is kept external to this function so that this code can
+ * can be written in an obvious, self documenting manner.
+ */
+static int
+xlog_write_setup_copy(
+ struct xlog_ticket *ticket,
+ struct xlog_op_header *ophdr,
+ int space_available,
+ int space_required,
+ int *copy_off,
+ int *copy_len,
+ int *last_was_partial_copy,
+ int *bytes_consumed)
+{
+ int still_to_copy;
+
+ still_to_copy = space_required - *bytes_consumed;
+ *copy_off = *bytes_consumed;
+
+ if (still_to_copy <= space_available) {
+ /* write of region completes here */
+ *copy_len = still_to_copy;
+ ophdr->oh_len = cpu_to_be32(*copy_len);
+ if (*last_was_partial_copy)
+ ophdr->oh_flags |= (XLOG_END_TRANS|XLOG_WAS_CONT_TRANS);
+ *last_was_partial_copy = 0;
+ *bytes_consumed = 0;
+ return 0;
+ }
+
+ /* partial write of region, needs extra log op header reservation */
+ *copy_len = space_available;
+ ophdr->oh_len = cpu_to_be32(*copy_len);
+ ophdr->oh_flags |= XLOG_CONTINUE_TRANS;
+ if (*last_was_partial_copy)
+ ophdr->oh_flags |= XLOG_WAS_CONT_TRANS;
+ *bytes_consumed += *copy_len;
+ (*last_was_partial_copy)++;
+
+ /* account for new log op header */
+ ticket->t_curr_res -= sizeof(struct xlog_op_header);
+ ticket->t_res_num_ophdrs++;
+
+ return sizeof(struct xlog_op_header);
+}
+
+static int
+xlog_write_copy_finish(
+ struct log *log,
+ struct xlog_in_core *iclog,
+ uint flags,
+ int *record_cnt,
+ int *data_cnt,
+ int *partial_copy,
+ int *partial_copy_len,
+ int log_offset,
+ struct xlog_in_core **commit_iclog)
+{
+ if (*partial_copy) {
+ /*
+ * This iclog has already been marked WANT_SYNC by
+ * xlog_state_get_iclog_space.
+ */
+ xlog_state_finish_copy(log, iclog, *record_cnt, *data_cnt);
+ *record_cnt = 0;
+ *data_cnt = 0;
+ return xlog_state_release_iclog(log, iclog);
+ }
+
+ *partial_copy = 0;
+ *partial_copy_len = 0;
+
+ if (iclog->ic_size - log_offset <= sizeof(xlog_op_header_t)) {
+ /* no more space in this iclog - push it. */
+ xlog_state_finish_copy(log, iclog, *record_cnt, *data_cnt);
+ *record_cnt = 0;
+ *data_cnt = 0;
+
+ spin_lock(&log->l_icloglock);
+ xlog_state_want_sync(log, iclog);
+ spin_unlock(&log->l_icloglock);
+
+ if (!commit_iclog)
+ return xlog_state_release_iclog(log, iclog);
+ ASSERT(flags & XLOG_COMMIT_TRANS);
+ *commit_iclog = iclog;
+ }
+
+ return 0;
+}
+
+/*
* Write some region out to in-core log
*
* This will be called when writing externally provided regions or when
@@ -1689,7 +1876,6 @@
int start_rec_copy; /* # bytes to copy for start record */
int partial_copy; /* did we split a region? */
int partial_copy_len;/* # bytes copied if split region */
- int need_copy; /* # bytes need to memcpy this region */
int copy_len; /* # bytes actually memcpy'ing */
int copy_off; /* # bytes from entry start */
int contwr; /* continued write of in-core log? */
@@ -1697,24 +1883,9 @@
int record_cnt = 0, data_cnt = 0;
partial_copy_len = partial_copy = 0;
-
- /* Calculate potential maximum space. Each region gets its own
- * xlog_op_header_t and may need to be double word aligned.
- */
- len = 0;
- if (ticket->t_flags & XLOG_TIC_INITED) { /* acct for start rec of xact */
- len += sizeof(xlog_op_header_t);
- ticket->t_res_num_ophdrs++;
- }
-
- for (index = 0; index < nentries; index++) {
- len += sizeof(xlog_op_header_t); /* each region gets >= 1 */
- ticket->t_res_num_ophdrs++;
- len += reg[index].i_len;
- xlog_tic_add_region(ticket, reg[index].i_len, reg[index].i_type);
- }
contwr = *start_lsn = 0;
+ len = xlog_write_calc_vec_length(ticket, reg, nentries);
if (ticket->t_curr_res < len) {
xlog_print_tic_res(mp, ticket);
#ifdef DEBUG
@@ -1748,81 +1919,23 @@
while (index < nentries) {
ASSERT(reg[index].i_len % sizeof(__int32_t) == 0);
ASSERT((__psint_t)ptr % sizeof(__int32_t) == 0);
- start_rec_copy = 0;
- /* If first write for transaction, insert start record.
- * We can't be trying to commit if we are inited. We can't
- * have any "partial_copy" if we are inited.
- */
- if (ticket->t_flags & XLOG_TIC_INITED) {
- logop_head = (xlog_op_header_t *)ptr;
- logop_head->oh_tid = cpu_to_be32(ticket->t_tid);
- logop_head->oh_clientid = ticket->t_clientid;
- logop_head->oh_len = 0;
- logop_head->oh_flags = XLOG_START_TRANS;
- logop_head->oh_res2 = 0;
- ticket->t_flags &= ~XLOG_TIC_INITED; /* clear bit */
+ start_rec_copy = xlog_write_start_rec(ptr, ticket);
+ if (start_rec_copy) {
record_cnt++;
-
- start_rec_copy = sizeof(xlog_op_header_t);
xlog_write_adv_cnt(ptr, len, log_offset, start_rec_copy);
}
- /* Copy log operation header directly into data section */
- logop_head = (xlog_op_header_t *)ptr;
- logop_head->oh_tid = cpu_to_be32(ticket->t_tid);
- logop_head->oh_clientid = ticket->t_clientid;
- logop_head->oh_res2 = 0;
-
- /* header copied directly */
+ logop_head = xlog_write_setup_ophdr(log, ptr, ticket, flags);
+ if (!logop_head)
+ return XFS_ERROR(EIO);
xlog_write_adv_cnt(ptr, len, log_offset, sizeof(xlog_op_header_t));
- /* are we copying a commit or unmount record? */
- logop_head->oh_flags = flags;
-
- /*
- * We've seen logs corrupted with bad transaction client
- * ids. This makes sure that XFS doesn't generate them on.
- * Turn this into an EIO and shut down the filesystem.
- */
- switch (logop_head->oh_clientid) {
- case XFS_TRANSACTION:
- case XFS_VOLUME:
- case XFS_LOG:
- break;
- default:
- xfs_fs_cmn_err(CE_WARN, mp,
- "Bad XFS transaction clientid 0x%x in ticket 0x%p",
- logop_head->oh_clientid, ticket);
- return XFS_ERROR(EIO);
- }
-
- /* Partial write last time? => (partial_copy != 0)
- * need_copy is the amount we'd like to copy if everything could
- * fit in the current memcpy.
- */
- need_copy = reg[index].i_len - partial_copy_len;
-
- copy_off = partial_copy_len;
- if (need_copy <= iclog->ic_size - log_offset) { /*complete write */
- copy_len = need_copy;
- logop_head->oh_len = cpu_to_be32(copy_len);
- if (partial_copy)
- logop_head->oh_flags|= (XLOG_END_TRANS|XLOG_WAS_CONT_TRANS);
- partial_copy_len = partial_copy = 0;
- } else { /* partial write */
- copy_len = iclog->ic_size - log_offset;
- logop_head->oh_len = cpu_to_be32(copy_len);
- logop_head->oh_flags |= XLOG_CONTINUE_TRANS;
- if (partial_copy)
- logop_head->oh_flags |= XLOG_WAS_CONT_TRANS;
- partial_copy_len += copy_len;
- partial_copy++;
- len += sizeof(xlog_op_header_t); /* from splitting of region */
- /* account for new log op header */
- ticket->t_curr_res -= sizeof(xlog_op_header_t);
- ticket->t_res_num_ophdrs++;
- }
+ len += xlog_write_setup_copy(ticket, logop_head,
+ iclog->ic_size - log_offset,
+ reg[index].i_len, ©_off,
+ ©_len, &partial_copy,
+ &partial_copy_len);
xlog_verify_dest_ptr(log, ptr);
/* copy region */
@@ -1834,34 +1947,34 @@
copy_len += start_rec_copy + sizeof(xlog_op_header_t);
record_cnt++;
data_cnt += contwr ? copy_len : 0;
- if (partial_copy) { /* copied partial region */
- /* already marked WANT_SYNC by xlog_state_get_iclog_space */
- xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
- record_cnt = data_cnt = 0;
- if ((error = xlog_state_release_iclog(log, iclog)))
- return error;
- break; /* don't increment index */
- } else { /* copied entire region */
- index++;
- partial_copy_len = partial_copy = 0;
- if (iclog->ic_size - log_offset <= sizeof(xlog_op_header_t)) {
- xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
- record_cnt = data_cnt = 0;
- spin_lock(&log->l_icloglock);
- xlog_state_want_sync(log, iclog);
- spin_unlock(&log->l_icloglock);
- if (commit_iclog) {
- ASSERT(flags & XLOG_COMMIT_TRANS);
- *commit_iclog = iclog;
- } else if ((error = xlog_state_release_iclog(log, iclog)))
- return error;
- if (index == nentries)
- return 0; /* we are done */
- else
- break;
- }
- } /* if (partial_copy) */
+ error = xlog_write_copy_finish(log, iclog, flags,
+ &record_cnt, &data_cnt,
+ &partial_copy, &partial_copy_len,
+ log_offset, commit_iclog);
+ if (error)
+ return error;
+
+ /*
+ * if we had a partial copy, we need to get more iclog
+ * space but we don't want to increment the region
+ * index because there is still more is this region to write.
+ *
+ * If we completed writing this region, and we flushed
+ * the iclog (indicated by resetting of the record
+ * count), then we also need to get more log space. If
+ * this was the last record, though, we are done and
+ * can just return.
+ */
+ if (partial_copy)
+ break;
+
+ index++;
+ if (record_cnt == 0) {
+ if (index == nentries)
+ return 0;
+ break;
+ }
} /* while (index < nentries) */
} /* for (index = 0; index < nentries; ) */
ASSERT(len == 0);