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NFS: Fix deadlocks in nfs_scan_commit_list()

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Partially revert commit 2ce209c42c ("NFS: Wait for requests that are
locked on the commit list"), since it can lead to deadlocks between
commit requests and nfs_join_page_group().
For now we should assume that any locked requests on the commit list are
either about to be removed and committed by another task, or the writes
they describe are about to be retransmitted. In either case, we should
not need to worry.

Fixes: 2ce209c42c ("NFS: Wait for requests that are locked on the commit list")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust 2021-10-04 15:44:16 -04:00
parent 110cb2d2f9
commit 64a93dbf25
1 changed files with 2 additions and 15 deletions
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17
fs/nfs/write.c
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@ -1039,25 +1039,11 @@ nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
struct nfs_page *req, *tmp;
int ret = 0;
restart:
list_for_each_entry_safe(req, tmp, src, wb_list) {
kref_get(&req->wb_kref);
if (!nfs_lock_request(req)) {
int status;
/* Prevent deadlock with nfs_lock_and_join_requests */
if (!list_empty(dst)) {
nfs_release_request(req);
continue;
}
/* Ensure we make progress to prevent livelock */
mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
status = nfs_wait_on_request(req);
nfs_release_request(req);
mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
if (status < 0)
break;
goto restart;
continue;
}
nfs_request_remove_commit_list(req, cinfo);
clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
@ -1952,6 +1938,7 @@ static int __nfs_commit_inode(struct inode *inode, int how,
int may_wait = how & FLUSH_SYNC;
int ret, nscan;
how &= ~FLUSH_SYNC;
nfs_init_cinfo_from_inode(&cinfo, inode);
nfs_commit_begin(cinfo.mds);
for (;;) {