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NFS: Clean up nfs_lock_and_join_requests()

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Clean up nfs_lock_and_join_requests() to simplify the calculation
of the range covered by the page group, taking into account the
presence of mirrors.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust
2020-03-30 11:12:16 -04:00
parent 377840ee48
commit a62f8e3bd8
3 changed files with 95 additions and 71 deletions
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91
fs/nfs/write.c
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@@ -379,34 +379,6 @@ static void nfs_end_page_writeback(struct nfs_page *req)
clear_bdi_congested(inode_to_bdi(inode), BLK_RW_ASYNC);
}
/*
* nfs_unroll_locks_and_wait - unlock all newly locked reqs and wait on @req
*
* this is a helper function for nfs_lock_and_join_requests
*
* @inode - inode associated with request page group, must be holding inode lock
* @head - head request of page group, must be holding head lock
* @req - request that couldn't lock and needs to wait on the req bit lock
*
* NOTE: this must be called holding page_group bit lock
* which will be released before returning.
*
* returns 0 on success, < 0 on error.
*/
static void
nfs_unroll_locks(struct inode *inode, struct nfs_page *head,
struct nfs_page *req)
{
struct nfs_page *tmp;
/* relinquish all the locks successfully grabbed this run */
for (tmp = head->wb_this_page ; tmp != req; tmp = tmp->wb_this_page) {
if (!kref_read(&tmp->wb_kref))
continue;
nfs_unlock_and_release_request(tmp);
}
}
/*
* nfs_destroy_unlinked_subrequests - destroy recently unlinked subrequests
*
@@ -487,7 +459,7 @@ nfs_lock_and_join_requests(struct page *page)
struct inode *inode = page_file_mapping(page)->host;
struct nfs_page *head, *subreq;
struct nfs_page *destroy_list = NULL;
unsigned int total_bytes;
unsigned int pgbase, off, bytes;
int ret;
try_again:
@@ -520,49 +492,30 @@ try_again:
goto release_request;
/* lock each request in the page group */
total_bytes = head->wb_bytes;
ret = nfs_page_group_lock_subrequests(head);
if (ret < 0)
goto release_request;
pgbase = head->wb_pgbase;
bytes = head->wb_bytes;
off = head->wb_offset;
for (subreq = head->wb_this_page; subreq != head;
subreq = subreq->wb_this_page) {
if (!kref_get_unless_zero(&subreq->wb_kref)) {
if (subreq->wb_offset == head->wb_offset + total_bytes)
total_bytes += subreq->wb_bytes;
continue;
}
while (!nfs_lock_request(subreq)) {
/*
* Unlock page to allow nfs_page_group_sync_on_bit()
* to succeed
*/
nfs_page_group_unlock(head);
ret = nfs_wait_on_request(subreq);
if (!ret)
ret = nfs_page_group_lock(head);
if (ret < 0) {
nfs_unroll_locks(inode, head, subreq);
nfs_release_request(subreq);
goto release_request;
}
}
/*
* Subrequests are always contiguous, non overlapping
* and in order - but may be repeated (mirrored writes).
*/
if (subreq->wb_offset == (head->wb_offset + total_bytes)) {
/* keep track of how many bytes this group covers */
total_bytes += subreq->wb_bytes;
} else if (WARN_ON_ONCE(subreq->wb_offset < head->wb_offset ||
((subreq->wb_offset + subreq->wb_bytes) >
(head->wb_offset + total_bytes)))) {
nfs_page_group_unlock(head);
nfs_unroll_locks(inode, head, subreq);
nfs_unlock_and_release_request(subreq);
ret = -EIO;
goto release_request;
/* Subrequests should always form a contiguous range */
if (pgbase > subreq->wb_pgbase) {
off -= pgbase - subreq->wb_pgbase;
bytes += pgbase - subreq->wb_pgbase;
pgbase = subreq->wb_pgbase;
}
bytes = max(subreq->wb_pgbase + subreq->wb_bytes
- pgbase, bytes);
}
/* Set the head request's range to cover the former page group */
head->wb_pgbase = pgbase;
head->wb_bytes = bytes;
head->wb_offset = off;
/* Now that all requests are locked, make sure they aren't on any list.
* Commit list removal accounting is done after locks are dropped */
subreq = head;
@@ -576,10 +529,6 @@ try_again:
/* destroy list will be terminated by head */
destroy_list = head->wb_this_page;
head->wb_this_page = head;
/* change head request to cover whole range that
* the former page group covered */
head->wb_bytes = total_bytes;
}
/* Postpone destruction of this request */