| Message ID | 20210305051143.182133-29-david@fromorbit.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xfs: consolidated log and optimisation changes | expand |
On Fri, Mar 05, 2021 at 04:11:26PM +1100, Dave Chinner wrote: > From: Dave Chinner <dchinner@redhat.com> > > Introduce an optimised version of xlog_write() that is used when the > entire write will fit in a single iclog. This greatly simplifies the > implementation of writing a log vector chain into an iclog, and sets > the ground work for a much more understandable xlog_write() > implementation. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/xfs/xfs_log.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 56 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index 22f97914ab99..590c1e6db475 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -2214,6 +2214,52 @@ xlog_write_copy_finish( > return error; > } > > +/* > + * Write log vectors into a single iclog which is guaranteed by the caller > + * to have enough space to write the entire log vector into. Return the number > + * of log vectors written into the iclog. > + */ > +static int > +xlog_write_single( > + struct xfs_log_vec *log_vector, > + struct xlog_ticket *ticket, > + struct xlog_in_core *iclog, > + uint32_t log_offset, > + uint32_t len) > +{ > + struct xfs_log_vec *lv = log_vector; > + void *ptr; > + int index = 0; > + int record_cnt = 0; Any reason these (and the return type) can't be unsigned? I don't think negative indices or record counts have any meaning, right? Otherwise this looks ok to me. --D > + > + ASSERT(log_offset + len <= iclog->ic_size); > + > + ptr = iclog->ic_datap + log_offset; > + for (lv = log_vector; lv; lv = lv->lv_next) { > + /* > + * Ordered log vectors have no regions to write so this > + * loop will naturally skip them. > + */ > + for (index = 0; index < lv->lv_niovecs; index++) { > + struct xfs_log_iovec *reg = &lv->lv_iovecp[index]; > + struct xlog_op_header *ophdr = reg->i_addr; > + > + ASSERT(reg->i_len % sizeof(int32_t) == 0); > + ASSERT((unsigned long)ptr % sizeof(int32_t) == 0); > + > + ophdr->oh_tid = cpu_to_be32(ticket->t_tid); > + ophdr->oh_len = cpu_to_be32(reg->i_len - > + sizeof(struct xlog_op_header)); > + memcpy(ptr, reg->i_addr, reg->i_len); > + xlog_write_adv_cnt(&ptr, &len, &log_offset, reg->i_len); > + record_cnt++; > + } > + } > + ASSERT(len == 0); > + return record_cnt; > +} > + > + > /* > * Write some region out to in-core log > * > @@ -2294,7 +2340,6 @@ xlog_write( > return error; > > ASSERT(log_offset <= iclog->ic_size - 1); > - ptr = iclog->ic_datap + log_offset; > > /* Start_lsn is the first lsn written to. */ > if (start_lsn && !*start_lsn) > @@ -2311,10 +2356,20 @@ xlog_write( > XLOG_ICL_NEED_FUA); > } > > + /* If this is a single iclog write, go fast... */ > + if (!contwr && lv == log_vector) { > + record_cnt = xlog_write_single(lv, ticket, iclog, > + log_offset, len); > + len = 0; > + data_cnt = len; > + break; > + } > + > /* > * This loop writes out as many regions as can fit in the amount > * of space which was allocated by xlog_state_get_iclog_space(). > */ > + ptr = iclog->ic_datap + log_offset; > while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) { > struct xfs_log_iovec *reg; > struct xlog_op_header *ophdr; > -- > 2.28.0 >
On Mon, Mar 08, 2021 at 06:39:27PM -0800, Darrick J. Wong wrote: > On Fri, Mar 05, 2021 at 04:11:26PM +1100, Dave Chinner wrote: > > From: Dave Chinner <dchinner@redhat.com> > > > > Introduce an optimised version of xlog_write() that is used when the > > entire write will fit in a single iclog. This greatly simplifies the > > implementation of writing a log vector chain into an iclog, and sets > > the ground work for a much more understandable xlog_write() > > implementation. > > > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > > --- > > fs/xfs/xfs_log.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 56 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > > index 22f97914ab99..590c1e6db475 100644 > > --- a/fs/xfs/xfs_log.c > > +++ b/fs/xfs/xfs_log.c > > @@ -2214,6 +2214,52 @@ xlog_write_copy_finish( > > return error; > > } > > > > +/* > > + * Write log vectors into a single iclog which is guaranteed by the caller > > + * to have enough space to write the entire log vector into. Return the number > > + * of log vectors written into the iclog. > > + */ > > +static int > > +xlog_write_single( > > + struct xfs_log_vec *log_vector, > > + struct xlog_ticket *ticket, > > + struct xlog_in_core *iclog, > > + uint32_t log_offset, > > + uint32_t len) > > +{ > > + struct xfs_log_vec *lv = log_vector; > > + void *ptr; > > + int index = 0; > > + int record_cnt = 0; > > Any reason these (and the return type) can't be unsigned? I don't think > negative indices or record counts have any meaning, right? Correct, but I'm going to ignore that because the next patch already addresses both of these things. Changing it here just means a massive reject of the next patch where it replaces the return value with a log vector, and the record count moves to a function parameter that is, indeed, a uint32_t. Cheers, Dave.
On Fri, Mar 05, 2021 at 04:11:26PM +1100, Dave Chinner wrote: > From: Dave Chinner <dchinner@redhat.com> > > Introduce an optimised version of xlog_write() that is used when the > entire write will fit in a single iclog. This greatly simplifies the > implementation of writing a log vector chain into an iclog, and sets > the ground work for a much more understandable xlog_write() > implementation. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/xfs/xfs_log.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 56 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index 22f97914ab99..590c1e6db475 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -2214,6 +2214,52 @@ xlog_write_copy_finish( > return error; > } > > +/* > + * Write log vectors into a single iclog which is guaranteed by the caller > + * to have enough space to write the entire log vector into. Return the number > + * of log vectors written into the iclog. > + */ > +static int > +xlog_write_single( > + struct xfs_log_vec *log_vector, > + struct xlog_ticket *ticket, > + struct xlog_in_core *iclog, > + uint32_t log_offset, > + uint32_t len) > +{ > + struct xfs_log_vec *lv = log_vector; This is initialized here and in the loop below. > + void *ptr; > + int index = 0; > + int record_cnt = 0; > + > + ASSERT(log_offset + len <= iclog->ic_size); > + > + ptr = iclog->ic_datap + log_offset; > + for (lv = log_vector; lv; lv = lv->lv_next) { > + /* > + * Ordered log vectors have no regions to write so this > + * loop will naturally skip them. > + */ > + for (index = 0; index < lv->lv_niovecs; index++) { > + struct xfs_log_iovec *reg = &lv->lv_iovecp[index]; > + struct xlog_op_header *ophdr = reg->i_addr; > + > + ASSERT(reg->i_len % sizeof(int32_t) == 0); > + ASSERT((unsigned long)ptr % sizeof(int32_t) == 0); > + > + ophdr->oh_tid = cpu_to_be32(ticket->t_tid); > + ophdr->oh_len = cpu_to_be32(reg->i_len - > + sizeof(struct xlog_op_header)); Perhaps we should retain the xlog_verify_dest_ptr() call here? It's DEBUG code and otherwise compiled out, so shouldn't impact production > + memcpy(ptr, reg->i_addr, reg->i_len); > + xlog_write_adv_cnt(&ptr, &len, &log_offset, reg->i_len); > + record_cnt++; > + } > + } > + ASSERT(len == 0); > + return record_cnt; > +} > + > + > /* > * Write some region out to in-core log > * > @@ -2294,7 +2340,6 @@ xlog_write( > return error; > > ASSERT(log_offset <= iclog->ic_size - 1); > - ptr = iclog->ic_datap + log_offset; > > /* Start_lsn is the first lsn written to. */ > if (start_lsn && !*start_lsn) > @@ -2311,10 +2356,20 @@ xlog_write( > XLOG_ICL_NEED_FUA); > } > > + /* If this is a single iclog write, go fast... */ > + if (!contwr && lv == log_vector) { > + record_cnt = xlog_write_single(lv, ticket, iclog, > + log_offset, len); > + len = 0; I assume this is here to satisfy the assert further down in the function.. This seems a bit contrived when you consider we pass len to the helper, the helper reduces it and asserts that it goes to zero, then we do so again here just for another assert. Unless this is all just removed later, it might be more straightforward to pass a reference. > + data_cnt = len; Similarly, this looks a bit odd because it seems data_cnt should be zero in the case where contwr == 0. xlog_state_get_iclog_space() has already bumped ->ic_offset by len (so xlog_state_finish_copy() doesn't need to via data_cnt). Brian > + break; > + } > + > /* > * This loop writes out as many regions as can fit in the amount > * of space which was allocated by xlog_state_get_iclog_space(). > */ > + ptr = iclog->ic_datap + log_offset; > while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) { > struct xfs_log_iovec *reg; > struct xlog_op_header *ophdr; > -- > 2.28.0 >
On Tue, Mar 16, 2021 at 02:39:59PM -0400, Brian Foster wrote: > On Fri, Mar 05, 2021 at 04:11:26PM +1100, Dave Chinner wrote: > > From: Dave Chinner <dchinner@redhat.com> > > > > Introduce an optimised version of xlog_write() that is used when the > > entire write will fit in a single iclog. This greatly simplifies the > > implementation of writing a log vector chain into an iclog, and sets > > the ground work for a much more understandable xlog_write() > > implementation. > > > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > > --- > > fs/xfs/xfs_log.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 56 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > > index 22f97914ab99..590c1e6db475 100644 > > --- a/fs/xfs/xfs_log.c > > +++ b/fs/xfs/xfs_log.c > > @@ -2214,6 +2214,52 @@ xlog_write_copy_finish( > > return error; > > } > > > > +/* > > + * Write log vectors into a single iclog which is guaranteed by the caller > > + * to have enough space to write the entire log vector into. Return the number > > + * of log vectors written into the iclog. > > + */ > > +static int > > +xlog_write_single( > > + struct xfs_log_vec *log_vector, > > + struct xlog_ticket *ticket, > > + struct xlog_in_core *iclog, > > + uint32_t log_offset, > > + uint32_t len) > > +{ > > + struct xfs_log_vec *lv = log_vector; > > This is initialized here and in the loop below. Fixed. > > > + void *ptr; > > + int index = 0; > > + int record_cnt = 0; > > + > > + ASSERT(log_offset + len <= iclog->ic_size); > > + > > + ptr = iclog->ic_datap + log_offset; > > + for (lv = log_vector; lv; lv = lv->lv_next) { > > + /* > > + * Ordered log vectors have no regions to write so this > > + * loop will naturally skip them. > > + */ > > + for (index = 0; index < lv->lv_niovecs; index++) { > > + struct xfs_log_iovec *reg = &lv->lv_iovecp[index]; > > + struct xlog_op_header *ophdr = reg->i_addr; > > + > > + ASSERT(reg->i_len % sizeof(int32_t) == 0); > > + ASSERT((unsigned long)ptr % sizeof(int32_t) == 0); > > + > > + ophdr->oh_tid = cpu_to_be32(ticket->t_tid); > > + ophdr->oh_len = cpu_to_be32(reg->i_len - > > + sizeof(struct xlog_op_header)); > > Perhaps we should retain the xlog_verify_dest_ptr() call here? It's > DEBUG code and otherwise compiled out, so shouldn't impact production The pointer check does nothing to actually prevent memory corruption. It only catches problems after we've already memcpy()d off the end of the iclog in the previous loop. So if the last region overruns the log, then it won't be triggered. And, well, we've already checked and asserted that the copy is going to fit entirely within the current iclog, so checking whether the pointer has overrun outside the iclog buffer is both redundant and too late. Hence I removed it... > > + memcpy(ptr, reg->i_addr, reg->i_len); > > + xlog_write_adv_cnt(&ptr, &len, &log_offset, reg->i_len); > > + record_cnt++; > > + } > > + } > > + ASSERT(len == 0); > > + return record_cnt; > > +} > > + > > + > > /* > > * Write some region out to in-core log > > * > > @@ -2294,7 +2340,6 @@ xlog_write( > > return error; > > > > ASSERT(log_offset <= iclog->ic_size - 1); > > - ptr = iclog->ic_datap + log_offset; > > > > /* Start_lsn is the first lsn written to. */ > > if (start_lsn && !*start_lsn) > > @@ -2311,10 +2356,20 @@ xlog_write( > > XLOG_ICL_NEED_FUA); > > } > > > > + /* If this is a single iclog write, go fast... */ > > + if (!contwr && lv == log_vector) { > > + record_cnt = xlog_write_single(lv, ticket, iclog, > > + log_offset, len); > > + len = 0; > > I assume this is here to satisfy the assert further down in the > function.. This seems a bit contrived when you consider we pass len to > the helper, the helper reduces it and asserts that it goes to zero, then > we do so again here just for another assert. Unless this is all just > removed later, it might be more straightforward to pass a reference. > > > + data_cnt = len; > > Similarly, this looks a bit odd because it seems data_cnt should be zero > in the case where contwr == 0. xlog_state_get_iclog_space() has already > bumped ->ic_offset by len (so xlog_state_finish_copy() doesn't need to > via data_cnt). Yes, it's entirely contrived to make it possible to split this code out in a simple fashion to ease review of the simple, fast path case this code will end up with. The next patch changes all this context and the parameters passed to the function, but this was the only way I could easily split the complex xlog_write() rewrite change into something a little bit simpler.... Cheers, Dave.
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 22f97914ab99..590c1e6db475 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -2214,6 +2214,52 @@ xlog_write_copy_finish( return error; } +/* + * Write log vectors into a single iclog which is guaranteed by the caller + * to have enough space to write the entire log vector into. Return the number + * of log vectors written into the iclog. + */ +static int +xlog_write_single( + struct xfs_log_vec *log_vector, + struct xlog_ticket *ticket, + struct xlog_in_core *iclog, + uint32_t log_offset, + uint32_t len) +{ + struct xfs_log_vec *lv = log_vector; + void *ptr; + int index = 0; + int record_cnt = 0; + + ASSERT(log_offset + len <= iclog->ic_size); + + ptr = iclog->ic_datap + log_offset; + for (lv = log_vector; lv; lv = lv->lv_next) { + /* + * Ordered log vectors have no regions to write so this + * loop will naturally skip them. + */ + for (index = 0; index < lv->lv_niovecs; index++) { + struct xfs_log_iovec *reg = &lv->lv_iovecp[index]; + struct xlog_op_header *ophdr = reg->i_addr; + + ASSERT(reg->i_len % sizeof(int32_t) == 0); + ASSERT((unsigned long)ptr % sizeof(int32_t) == 0); + + ophdr->oh_tid = cpu_to_be32(ticket->t_tid); + ophdr->oh_len = cpu_to_be32(reg->i_len - + sizeof(struct xlog_op_header)); + memcpy(ptr, reg->i_addr, reg->i_len); + xlog_write_adv_cnt(&ptr, &len, &log_offset, reg->i_len); + record_cnt++; + } + } + ASSERT(len == 0); + return record_cnt; +} + + /* * Write some region out to in-core log * @@ -2294,7 +2340,6 @@ xlog_write( return error; ASSERT(log_offset <= iclog->ic_size - 1); - ptr = iclog->ic_datap + log_offset; /* Start_lsn is the first lsn written to. */ if (start_lsn && !*start_lsn) @@ -2311,10 +2356,20 @@ xlog_write( XLOG_ICL_NEED_FUA); } + /* If this is a single iclog write, go fast... */ + if (!contwr && lv == log_vector) { + record_cnt = xlog_write_single(lv, ticket, iclog, + log_offset, len); + len = 0; + data_cnt = len; + break; + } + /* * This loop writes out as many regions as can fit in the amount * of space which was allocated by xlog_state_get_iclog_space(). */ + ptr = iclog->ic_datap + log_offset; while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) { struct xfs_log_iovec *reg; struct xlog_op_header *ophdr;