The function `ceph_writepages_start()` triggers
a large stack frame warning:
ld.lld: warning:
fs/ceph/addr.c:1632:0: stack frame size (1072) exceeds limit (1024) in function 'ceph_writepages_start.llvm.2555023190050417194'
fix it by dynamically allocating `ceph_writeback_ctl` struct.
Signed-off-by: Abinash Singh <abinashsinghlalotra@xxxxxxxxx>
---
The high stack usage of ceph_writepages_start() was further
confirmed by using -fstack-usage flag :
...
fs/ceph/addr.c:1837:ceph_netfs_check_write_begin 104 static
fs/ceph/addr.c:1630:ceph_writepages_start 648 static
...
After optimzations it may go upto 1072 as seen in warning.
After allocating `ceph_writeback_ctl` struct it is reduced to:
...
fs/ceph/addr.c:1630:ceph_writepages_start 288 static
fs/ceph/addr.c:81:ceph_dirty_folio 72 static
...
Is this fun used very frequently ?? or dynamic allocation is
a fine fix for reducing the stack usage ?
Thank You
---
fs/ceph/addr.c | 82 ++++++++++++++++++++++++++------------------------
1 file changed, 43 insertions(+), 39 deletions(-)
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 60a621b00c65..503a86c1dda6 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1633,9 +1633,13 @@ static int ceph_writepages_start(struct address_space *mapping,
struct inode *inode = mapping->host;
struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
struct ceph_client *cl = fsc->client;
- struct ceph_writeback_ctl ceph_wbc;
+ struct ceph_writeback_ctl *ceph_wbc __free(kfree) = NULL;
int rc = 0;
+ ceph_wbc = kmalloc(sizeof(*ceph_wbc), GFP_NOFS);
+ if (!ceph_wbc)
+ return -ENOMEM;
+
if (wbc->sync_mode == WB_SYNC_NONE && fsc->write_congested)
return 0;
@@ -1648,7 +1652,7 @@ static int ceph_writepages_start(struct address_space *mapping,
return -EIO;
}
- ceph_init_writeback_ctl(mapping, wbc, &ceph_wbc);
+ ceph_init_writeback_ctl(mapping, wbc, ceph_wbc);
if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
rc = -EIO;
@@ -1656,7 +1660,7 @@ static int ceph_writepages_start(struct address_space *mapping,
}
retry:
- rc = ceph_define_writeback_range(mapping, wbc, &ceph_wbc);
+ rc = ceph_define_writeback_range(mapping, wbc, ceph_wbc);
if (rc == -ENODATA) {
/* hmm, why does writepages get called when there
is no dirty data? */
@@ -1665,55 +1669,55 @@ static int ceph_writepages_start(struct address_space *mapping,
}
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
- tag_pages_for_writeback(mapping, ceph_wbc.index, ceph_wbc.end);
+ tag_pages_for_writeback(mapping, ceph_wbc->index, ceph_wbc->end);
- while (!has_writeback_done(&ceph_wbc)) {
- ceph_wbc.locked_pages = 0;
- ceph_wbc.max_pages = ceph_wbc.wsize >> PAGE_SHIFT;
+ while (!has_writeback_done(ceph_wbc)) {
+ ceph_wbc->locked_pages = 0;
+ ceph_wbc->max_pages = ceph_wbc->wsize >> PAGE_SHIFT;
get_more_pages:
- ceph_folio_batch_reinit(&ceph_wbc);
+ ceph_folio_batch_reinit(ceph_wbc);
- ceph_wbc.nr_folios = filemap_get_folios_tag(mapping,
- &ceph_wbc.index,
- ceph_wbc.end,
- ceph_wbc.tag,
- &ceph_wbc.fbatch);
+ ceph_wbc->nr_folios = filemap_get_folios_tag(mapping,
+ &ceph_wbc->index,
+ ceph_wbc->end,
+ ceph_wbc->tag,
+ &ceph_wbc->fbatch);
doutc(cl, "pagevec_lookup_range_tag for tag %#x got %d\n",
- ceph_wbc.tag, ceph_wbc.nr_folios);
+ ceph_wbc->tag, ceph_wbc->nr_folios);
- if (!ceph_wbc.nr_folios && !ceph_wbc.locked_pages)
+ if (!ceph_wbc->nr_folios && !ceph_wbc->locked_pages)
break;
process_folio_batch:
- rc = ceph_process_folio_batch(mapping, wbc, &ceph_wbc);
+ rc = ceph_process_folio_batch(mapping, wbc, ceph_wbc);
if (rc)
goto release_folios;
/* did we get anything? */
- if (!ceph_wbc.locked_pages)
+ if (!ceph_wbc->locked_pages)
goto release_folios;
- if (ceph_wbc.processed_in_fbatch) {
- ceph_shift_unused_folios_left(&ceph_wbc.fbatch);
+ if (ceph_wbc->processed_in_fbatch) {
+ ceph_shift_unused_folios_left(&ceph_wbc->fbatch);
- if (folio_batch_count(&ceph_wbc.fbatch) == 0 &&
- ceph_wbc.locked_pages < ceph_wbc.max_pages) {
+ if (folio_batch_count(&ceph_wbc->fbatch) == 0 &&
+ ceph_wbc->locked_pages < ceph_wbc->max_pages) {
doutc(cl, "reached end fbatch, trying for more\n");
goto get_more_pages;
}
}
- rc = ceph_submit_write(mapping, wbc, &ceph_wbc);
+ rc = ceph_submit_write(mapping, wbc, ceph_wbc);
if (rc)
goto release_folios;
- ceph_wbc.locked_pages = 0;
- ceph_wbc.strip_unit_end = 0;
+ ceph_wbc->locked_pages = 0;
+ ceph_wbc->strip_unit_end = 0;
- if (folio_batch_count(&ceph_wbc.fbatch) > 0) {
- ceph_wbc.nr_folios =
- folio_batch_count(&ceph_wbc.fbatch);
+ if (folio_batch_count(&ceph_wbc->fbatch) > 0) {
+ ceph_wbc->nr_folios =
+ folio_batch_count(&ceph_wbc->fbatch);
goto process_folio_batch;
}
@@ -1724,38 +1728,38 @@ static int ceph_writepages_start(struct address_space *mapping,
* we tagged for writeback prior to entering this loop.
*/
if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE)
- ceph_wbc.done = true;
+ ceph_wbc->done = true;
release_folios:
doutc(cl, "folio_batch release on %d folios (%p)\n",
- (int)ceph_wbc.fbatch.nr,
- ceph_wbc.fbatch.nr ? ceph_wbc.fbatch.folios[0] : NULL);
- folio_batch_release(&ceph_wbc.fbatch);
+ (int)ceph_wbc->fbatch.nr,
+ ceph_wbc->fbatch.nr ? ceph_wbc->fbatch.folios[0] : NULL);
+ folio_batch_release(&ceph_wbc->fbatch);
}
- if (ceph_wbc.should_loop && !ceph_wbc.done) {
+ if (ceph_wbc->should_loop && !ceph_wbc->done) {
/* more to do; loop back to beginning of file */
doutc(cl, "looping back to beginning of file\n");
/* OK even when start_index == 0 */
- ceph_wbc.end = ceph_wbc.start_index - 1;
+ ceph_wbc->end = ceph_wbc->start_index - 1;
/* to write dirty pages associated with next snapc,
* we need to wait until current writes complete */
- ceph_wait_until_current_writes_complete(mapping, wbc, &ceph_wbc);
+ ceph_wait_until_current_writes_complete(mapping, wbc, ceph_wbc);
- ceph_wbc.start_index = 0;
- ceph_wbc.index = 0;
+ ceph_wbc->start_index = 0;
+ ceph_wbc->index = 0;
goto retry;
}
- if (wbc->range_cyclic || (ceph_wbc.range_whole && wbc->nr_to_write > 0))
- mapping->writeback_index = ceph_wbc.index;
+ if (wbc->range_cyclic || (ceph_wbc->range_whole && wbc->nr_to_write > 0))
+ mapping->writeback_index = ceph_wbc->index;
dec_osd_stopping_blocker:
ceph_dec_osd_stopping_blocker(fsc->mdsc);
out:
- ceph_put_snap_context(ceph_wbc.last_snapc);
+ ceph_put_snap_context(ceph_wbc->last_snapc);
doutc(cl, "%llx.%llx dend - startone, rc = %d\n", ceph_vinop(inode),
rc);
--
2.43.0
