From: Jeff Layton jlayton@kernel.org
[ Upstream commit 4c475eee02375ade6e864f1db16976ba0d96a0a2 ]
Most of the time, NFSv4 clients issue a COMMIT before the final CLOSE of an open stateid, so with NFSv4, the fsync in the nfsd_file_free path is usually a no-op and doesn't block.
We have a customer running knfsd over very slow storage (XFS over Ceph RBD). They were using the "async" export option because performance was more important than data integrity for this application. That export option turns NFSv4 COMMIT calls into no-ops. Due to the fsync in this codepath however, their final CLOSE calls would still stall (since a CLOSE effectively became a COMMIT).
I think this fsync is not strictly necessary. We only use that result to reset the write verifier. Instead of fsync'ing all of the data when we free an nfsd_file, we can just check for writeback errors when one is acquired and when it is freed.
If the client never comes back, then it'll never see the error anyway and there is no point in resetting it. If an error occurs after the nfsd_file is removed from the cache but before the inode is evicted, then it will reset the write verifier on the next nfsd_file_acquire, (since there will be an unseen error).
The only exception here is if something else opens and fsyncs the file during that window. Given that local applications work with this limitation today, I don't see that as an issue.
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2166658 Fixes: ac3a2585f018 ("nfsd: rework refcounting in filecache") Reported-and-tested-by: Pierguido Lambri plambri@redhat.com Signed-off-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfsd/filecache.c | 44 ++++++++++++-------------------------------- fs/nfsd/trace.h | 31 ------------------------------- 2 files changed, 12 insertions(+), 63 deletions(-)
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 142b3c928f76e..5cb8cce153a57 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -309,37 +309,27 @@ nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsigned int may) return nf; }
+/** + * nfsd_file_check_write_error - check for writeback errors on a file + * @nf: nfsd_file to check for writeback errors + * + * Check whether a nfsd_file has an unseen error. Reset the write + * verifier if so. + */ static void -nfsd_file_fsync(struct nfsd_file *nf) -{ - struct file *file = nf->nf_file; - int ret; - - if (!file || !(file->f_mode & FMODE_WRITE)) - return; - ret = vfs_fsync(file, 1); - trace_nfsd_file_fsync(nf, ret); - if (ret) - nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); -} - -static int nfsd_file_check_write_error(struct nfsd_file *nf) { struct file *file = nf->nf_file;
- if (!file || !(file->f_mode & FMODE_WRITE)) - return 0; - return filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err)); + if ((file->f_mode & FMODE_WRITE) && + filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err))) + nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); }
static void nfsd_file_hash_remove(struct nfsd_file *nf) { trace_nfsd_file_unhash(nf); - - if (nfsd_file_check_write_error(nf)) - nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id)); rhashtable_remove_fast(&nfsd_file_rhash_tbl, &nf->nf_rhash, nfsd_file_rhash_params); } @@ -365,23 +355,12 @@ nfsd_file_free(struct nfsd_file *nf) this_cpu_add(nfsd_file_total_age, age);
nfsd_file_unhash(nf); - - /* - * We call fsync here in order to catch writeback errors. It's not - * strictly required by the protocol, but an nfsd_file could get - * evicted from the cache before a COMMIT comes in. If another - * task were to open that file in the interim and scrape the error, - * then the client may never see it. By calling fsync here, we ensure - * that writeback happens before the entry is freed, and that any - * errors reported result in the write verifier changing. - */ - nfsd_file_fsync(nf); - if (nf->nf_mark) nfsd_file_mark_put(nf->nf_mark); if (nf->nf_file) { get_file(nf->nf_file); filp_close(nf->nf_file, NULL); + nfsd_file_check_write_error(nf); fput(nf->nf_file); }
@@ -1136,6 +1115,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, out: if (status == nfs_ok) { this_cpu_inc(nfsd_file_acquisitions); + nfsd_file_check_write_error(nf); *pnf = nf; } else { if (refcount_dec_and_test(&nf->nf_ref)) diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h index 4eb4e1039c7f4..132335011ccae 100644 --- a/fs/nfsd/trace.h +++ b/fs/nfsd/trace.h @@ -1143,37 +1143,6 @@ TRACE_EVENT(nfsd_file_close, ) );
-TRACE_EVENT(nfsd_file_fsync, - TP_PROTO( - const struct nfsd_file *nf, - int ret - ), - TP_ARGS(nf, ret), - TP_STRUCT__entry( - __field(void *, nf_inode) - __field(int, nf_ref) - __field(int, ret) - __field(unsigned long, nf_flags) - __field(unsigned char, nf_may) - __field(struct file *, nf_file) - ), - TP_fast_assign( - __entry->nf_inode = nf->nf_inode; - __entry->nf_ref = refcount_read(&nf->nf_ref); - __entry->ret = ret; - __entry->nf_flags = nf->nf_flags; - __entry->nf_may = nf->nf_may; - __entry->nf_file = nf->nf_file; - ), - TP_printk("inode=%p ref=%d flags=%s may=%s nf_file=%p ret=%d", - __entry->nf_inode, - __entry->nf_ref, - show_nf_flags(__entry->nf_flags), - show_nfsd_may_flags(__entry->nf_may), - __entry->nf_file, __entry->ret - ) -); - #include "cache.h"
TRACE_DEFINE_ENUM(RC_DROPIT);