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xfs: factor xlog_write

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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>
This commit is contained in:
Dave Chinner 2010-03-23 11:29:44 +11:00 committed by Alex Elder
parent 9b9fc2b760
commit b5203cd0a4
1 changed files with 225 additions and 112 deletions
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337
fs/xfs/xfs_log.c
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@ -1629,6 +1629,193 @@ xlog_print_tic_res(xfs_mount_t *mp, xlog_ticket_t *ticket)
}
}
/*
* 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
*
@ -1689,7 +1876,6 @@ xlog_write(
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 @@ xlog_write(
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 @@ xlog_write(
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, &copy_off,
&copy_len, &partial_copy,
&partial_copy_len);
xlog_verify_dest_ptr(log, ptr);
/* copy region */
@ -1834,34 +1947,34 @@ xlog_write(
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);