From bd37d6fce184836bd5e7cd90ce40116a4fadaf2a Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Tue, 1 Aug 2017 12:06:30 -0400 Subject: [PATCH] NFSv4: Convert nfs_lock_and_join_requests() to use nfs_page_find_head_request() Hide the locking from nfs_lock_and_join_requests() so that we can separate out the requirements for swapcache pages. Signed-off-by: Trond Myklebust --- fs/nfs/write.c | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-) diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 759e37d..a06167e 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -154,6 +154,14 @@ static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error) set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags); } +static struct nfs_page * +nfs_page_private_request(struct page *page) +{ + if (!PagePrivate(page)) + return NULL; + return (struct nfs_page *)page_private(page); +} + /* * nfs_page_find_head_request_locked - find head request associated with @page * @@ -164,11 +172,10 @@ static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error) static struct nfs_page * nfs_page_find_head_request_locked(struct nfs_inode *nfsi, struct page *page) { - struct nfs_page *req = NULL; + struct nfs_page *req; - if (PagePrivate(page)) - req = (struct nfs_page *)page_private(page); - else if (unlikely(PageSwapCache(page))) + req = nfs_page_private_request(page); + if (!req && unlikely(PageSwapCache(page))) req = nfs_page_search_commits_for_head_request_locked(nfsi, page); @@ -448,31 +455,29 @@ nfs_lock_and_join_requests(struct page *page) int ret; try_again: - if (!(PagePrivate(page) || PageSwapCache(page))) - return NULL; - spin_lock(&inode->i_lock); /* * A reference is taken only on the head request which acts as a * reference to the whole page group - the group will not be destroyed * until the head reference is released. */ - head = nfs_page_find_head_request_locked(NFS_I(inode), page); - - if (!head) { - spin_unlock(&inode->i_lock); + head = nfs_page_find_head_request(page); + if (!head) return NULL; - } /* lock the page head first in order to avoid an ABBA inefficiency */ if (!nfs_lock_request(head)) { - spin_unlock(&inode->i_lock); ret = nfs_wait_on_request(head); nfs_release_request(head); if (ret < 0) return ERR_PTR(ret); goto try_again; } - spin_unlock(&inode->i_lock); + + /* Ensure that nobody removed the request before we locked it */ + if (head != nfs_page_private_request(page) && !PageSwapCache(page)) { + nfs_unlock_and_release_request(head); + goto try_again; + } ret = nfs_page_group_lock(head); if (ret < 0) { @@ -559,7 +564,7 @@ try_again: return NULL; } - /* still holds ref on head from nfs_page_find_head_request_locked + /* still holds ref on head from nfs_page_find_head_request * and still has lock on head from lock loop */ return head; } -- 2.7.4