ext4_writepages() currently works in a loop like:
start a transaction
scan inode for pages to write
map and submit these pages
stop the transaction
This loop results in starting transaction once more than is needed
because in the last iteration we start a transaction only to scan the
inode and find there are no pages to write. This can be significant
increase in number of transaction starts for single-extent files or
files that have all blocks already mapped. Furthermore we already know
from previous iteration whether there are more pages to write or not. So
propagate the information from mpage_prepare_extent_to_map() and avoid
unnecessary looping in case there are no more pages to write.
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200525081215.29451-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
struct ext4_map_blocks map;
struct ext4_io_submit io_submit; /* IO submission data */
unsigned int do_map:1;
struct ext4_map_blocks map;
struct ext4_io_submit io_submit; /* IO submission data */
unsigned int do_map:1;
+ unsigned int scanned_until_end:1;
};
static void mpage_release_unused_pages(struct mpage_da_data *mpd,
};
static void mpage_release_unused_pages(struct mpage_da_data *mpd,
if (mpd->first_page >= mpd->next_page)
return;
if (mpd->first_page >= mpd->next_page)
return;
+ mpd->scanned_until_end = 0;
index = mpd->first_page;
end = mpd->next_page - 1;
if (invalidate) {
index = mpd->first_page;
end = mpd->next_page - 1;
if (invalidate) {
if (err < 0)
return err;
}
if (err < 0)
return err;
}
+ if (lblk >= blocks) {
+ mpd->scanned_until_end = 1;
+ return 0;
+ }
+ return 1;
nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
tag);
if (nr_pages == 0)
nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
tag);
if (nr_pages == 0)
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
pagevec_release(&pvec);
cond_resched();
}
pagevec_release(&pvec);
cond_resched();
}
+ mpd->scanned_until_end = 1;
return 0;
out:
pagevec_release(&pvec);
return 0;
out:
pagevec_release(&pvec);
struct inode *inode = mapping->host;
int needed_blocks, rsv_blocks = 0, ret = 0;
struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
struct inode *inode = mapping->host;
int needed_blocks, rsv_blocks = 0, ret = 0;
struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
struct blk_plug plug;
bool give_up_on_write = false;
struct blk_plug plug;
bool give_up_on_write = false;
retry:
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
tag_pages_for_writeback(mapping, mpd.first_page, mpd.last_page);
retry:
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
tag_pages_for_writeback(mapping, mpd.first_page, mpd.last_page);
blk_start_plug(&plug);
/*
blk_start_plug(&plug);
/*
* started.
*/
mpd.do_map = 0;
* started.
*/
mpd.do_map = 0;
+ mpd.scanned_until_end = 0;
mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
if (!mpd.io_submit.io_end) {
ret = -ENOMEM;
mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
if (!mpd.io_submit.io_end) {
ret = -ENOMEM;
if (ret < 0)
goto unplug;
if (ret < 0)
goto unplug;
- while (!done && mpd.first_page <= mpd.last_page) {
+ while (!mpd.scanned_until_end && wbc->nr_to_write > 0) {
/* For each extent of pages we use new io_end */
mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
if (!mpd.io_submit.io_end) {
/* For each extent of pages we use new io_end */
mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
if (!mpd.io_submit.io_end) {
trace_ext4_da_write_pages(inode, mpd.first_page, mpd.wbc);
ret = mpage_prepare_extent_to_map(&mpd);
trace_ext4_da_write_pages(inode, mpd.first_page, mpd.wbc);
ret = mpage_prepare_extent_to_map(&mpd);
- if (!ret) {
- if (mpd.map.m_len)
- ret = mpage_map_and_submit_extent(handle, &mpd,
+ if (!ret && mpd.map.m_len)
+ ret = mpage_map_and_submit_extent(handle, &mpd,
- else {
- /*
- * We scanned the whole range (or exhausted
- * nr_to_write), submitted what was mapped and
- * didn't find anything needing mapping. We are
- * done.
- */
- done = true;
- }
- }
/*
* Caution: If the handle is synchronous,
* ext4_journal_stop() can wait for transaction commit
/*
* Caution: If the handle is synchronous,
* ext4_journal_stop() can wait for transaction commit