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fuse: clean up fuse_writepage_in_flight()

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Restructure the function to better separate the locked and the unlocked
parts.  Use the "old_req" local variable to mean only the queued request,
and not any auxiliary requests added onto its misc.write.next list.  These
changes are in preparation for the following patch.

Also turn BUG_ON instances into WARN_ON and add a header comment explaining
what the function does.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2019-01-16 10:27:59 +01:00
parent 2fe93bd432
commit 7f305ca192
1 changed files with 24 additions and 16 deletions
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40
fs/fuse/file.c
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@ -1744,6 +1744,13 @@ static void fuse_writepages_send(struct fuse_fill_wb_data *data)
end_page_writeback(data->orig_pages[i]);
}
/*
* First recheck under fi->lock if the offending offset is still under
* writeback. If yes, then iterate write requests, to see if there's one
* already added for a page at this offset. If there's none, then insert this
* new request onto the auxiliary list, otherwise reuse the existing one by
* copying the new page contents over to the old temporary page.
*/
static bool fuse_writepage_in_flight(struct fuse_req *new_req,
struct page *page)
{
@ -1751,9 +1758,8 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
struct fuse_inode *fi = get_fuse_inode(new_req->inode);
struct fuse_req *tmp;
struct fuse_req *old_req;
pgoff_t curr_index;
BUG_ON(new_req->num_pages != 0);
WARN_ON(new_req->num_pages != 0);
spin_lock(&fc->lock);
list_del(&new_req->writepages_entry);
@ -1766,32 +1772,34 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
new_req->num_pages = 1;
for (tmp = old_req; tmp != NULL; tmp = tmp->misc.write.next) {
BUG_ON(tmp->inode != new_req->inode);
pgoff_t curr_index;
WARN_ON(tmp->inode != new_req->inode);
curr_index = tmp->misc.write.in.offset >> PAGE_SHIFT;
if (tmp->num_pages == 1 &&
curr_index == page->index) {
old_req = tmp;
if (tmp->num_pages == 1 && curr_index == page->index &&
test_bit(FR_PENDING, &tmp->flags)) {
copy_highpage(tmp->pages[0], page);
break;
}
}
if (old_req->num_pages == 1 && test_bit(FR_PENDING, &old_req->flags)) {
struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host);
if (!tmp) {
new_req->misc.write.next = old_req->misc.write.next;
old_req->misc.write.next = new_req;
}
copy_highpage(old_req->pages[0], page);
spin_unlock(&fc->lock);
spin_unlock(&fc->lock);
if (tmp) {
struct backing_dev_info *bdi = inode_to_bdi(new_req->inode);
dec_wb_stat(&bdi->wb, WB_WRITEBACK);
dec_node_page_state(new_req->pages[0], NR_WRITEBACK_TEMP);
wb_writeout_inc(&bdi->wb);
fuse_writepage_free(fc, new_req);
fuse_request_free(new_req);
goto out;
} else {
new_req->misc.write.next = old_req->misc.write.next;
old_req->misc.write.next = new_req;
}
spin_unlock(&fc->lock);
out:
return true;
}