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ceph: break out writeback of incompatible snap context to separate function

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When dirtying a page, we have to flush incompatible contexts. Move the
search for an incompatible context into a separate function, and fix up
the caller to wait and retry if there is one.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Jeff Layton 2020-05-28 13:56:54 -04:00 committed by Ilya Dryomov
parent 4bb926e83f
commit 18d620f063
1 changed files with 68 additions and 46 deletions
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114
fs/ceph/addr.c
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@ -1298,6 +1298,62 @@ static int context_is_writeable_or_written(struct inode *inode,
return ret;
}
/**
* ceph_find_incompatible - find an incompatible context and return it
* @inode: inode associated with page
* @page: page being dirtied
*
* We are only allowed to write into/dirty a page if the page is
* clean, or already dirty within the same snap context. Returns a
* conflicting context if there is one, NULL if there isn't, or a
* negative error code on other errors.
*
* Must be called with page lock held.
*/
static struct ceph_snap_context *
ceph_find_incompatible(struct inode *inode, struct page *page)
{
struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
struct ceph_inode_info *ci = ceph_inode(inode);
if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
dout(" page %p forced umount\n", page);
return ERR_PTR(-EIO);
}
for (;;) {
struct ceph_snap_context *snapc, *oldest;
wait_on_page_writeback(page);
snapc = page_snap_context(page);
if (!snapc || snapc == ci->i_head_snapc)
break;
/*
* this page is already dirty in another (older) snap
* context! is it writeable now?
*/
oldest = get_oldest_context(inode, NULL, NULL);
if (snapc->seq > oldest->seq) {
/* not writeable -- return it for the caller to deal with */
ceph_put_snap_context(oldest);
dout(" page %p snapc %p not current or oldest\n", page, snapc);
return ceph_get_snap_context(snapc);
}
ceph_put_snap_context(oldest);
/* yay, writeable, do it now (without dropping page lock) */
dout(" page %p snapc %p not current, but oldest\n", page, snapc);
if (clear_page_dirty_for_io(page)) {
int r = writepage_nounlock(page, NULL);
if (r < 0)
return ERR_PTR(r);
}
}
return NULL;
}
/*
* We are only allowed to write into/dirty the page if the page is
* clean, or already dirty within the same snap context.
@ -1311,61 +1367,27 @@ static int ceph_update_writeable_page(struct file *file,
struct page *page)
{
struct inode *inode = file_inode(file);
struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
struct ceph_inode_info *ci = ceph_inode(inode);
struct ceph_snap_context *snapc;
loff_t page_off = pos & PAGE_MASK;
int pos_in_page = pos & ~PAGE_MASK;
int end_in_page = pos_in_page + len;
loff_t i_size;
int r;
struct ceph_snap_context *snapc, *oldest;
if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
dout(" page %p forced umount\n", page);
unlock_page(page);
return -EIO;
}
retry_locked:
/* writepages currently holds page lock, but if we change that later, */
wait_on_page_writeback(page);
snapc = page_snap_context(page);
if (snapc && snapc != ci->i_head_snapc) {
/*
* this page is already dirty in another (older) snap
* context! is it writeable now?
*/
oldest = get_oldest_context(inode, NULL, NULL);
if (snapc->seq > oldest->seq) {
ceph_put_snap_context(oldest);
dout(" page %p snapc %p not current or oldest\n",
page, snapc);
/*
* queue for writeback, and wait for snapc to
* be writeable or written
*/
snapc = ceph_get_snap_context(snapc);
unlock_page(page);
ceph_queue_writeback(inode);
r = wait_event_killable(ci->i_cap_wq,
context_is_writeable_or_written(inode, snapc));
ceph_put_snap_context(snapc);
if (r == -ERESTARTSYS)
return r;
return -EAGAIN;
}
ceph_put_snap_context(oldest);
/* yay, writeable, do it now (without dropping page lock) */
dout(" page %p snapc %p not current, but oldest\n",
page, snapc);
if (!clear_page_dirty_for_io(page))
goto retry_locked;
r = writepage_nounlock(page, NULL);
if (r < 0)
snapc = ceph_find_incompatible(inode, page);
if (snapc) {
if (IS_ERR(snapc)) {
r = PTR_ERR(snapc);
goto fail_unlock;
goto retry_locked;
}
unlock_page(page);
ceph_queue_writeback(inode);
r = wait_event_killable(ci->i_cap_wq,
context_is_writeable_or_written(inode, snapc));
ceph_put_snap_context(snapc);
return -EAGAIN;
}
if (PageUptodate(page)) {