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NFS: fix subtle change in COMMIT behavior 

Recent work in the pgio layer made it possible for there to be more than one
request per page. This caused a subtle change in commit behavior, because
write.c:nfs_commit_unstable_pages compares the number of *pages* waiting for
writeback against the number of requests on a commit list to choose when to
send a COMMIT in a non-blocking flush.

This is probably hard to hit in normal operation - you have to be using
rsize/wsize < PAGE_SIZE, or pnfs with lots of boundaries that are not page
aligned to have a noticeable change in behavior.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Weston Andros Adamson 2014-11-12 12:08:00 -05:00 committed by Trond Myklebust
parent 6a74c0c940
commit cb1410c71e
5 changed files with 27 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/nfs/callback_proc.c
View File

@ -49,7 +49,7 @@ __be32 nfs4_callback_getattr(struct cb_getattrargs *args,
goto out_iput;
res->size = i_size_read(inode);
res->change_attr = delegation->change_attr;
if (nfsi->npages != 0)
if (nfsi->nrequests != 0)
res->change_attr++;
res->ctime = inode->i_ctime;
res->mtime = inode->i_mtime;

8
fs/nfs/inode.c
View File

@ -1149,7 +1149,7 @@ static unsigned long nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr
if ((fattr->valid & NFS_ATTR_FATTR_PRESIZE)
&& (fattr->valid & NFS_ATTR_FATTR_SIZE)
&& i_size_read(inode) == nfs_size_to_loff_t(fattr->pre_size)
&& nfsi->npages == 0) {
&& nfsi->nrequests == 0) {
i_size_write(inode, nfs_size_to_loff_t(fattr->size));
ret |= NFS_INO_INVALID_ATTR;
}
@ -1192,7 +1192,7 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat
if (fattr->valid & NFS_ATTR_FATTR_SIZE) {
cur_size = i_size_read(inode);
new_isize = nfs_size_to_loff_t(fattr->size);
if (cur_size != new_isize && nfsi->npages == 0)
if (cur_size != new_isize && nfsi->nrequests == 0)
invalid |= NFS_INO_INVALID_ATTR|NFS_INO_REVAL_PAGECACHE;
}
@ -1619,7 +1619,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
if (new_isize != cur_isize) {
/* Do we perhaps have any outstanding writes, or has
* the file grown beyond our last write? */
if ((nfsi->npages == 0) || new_isize > cur_isize) {
if ((nfsi->nrequests == 0) || new_isize > cur_isize) {
i_size_write(inode, new_isize);
invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
invalid &= ~NFS_INO_REVAL_PAGECACHE;
@ -1784,7 +1784,7 @@ static void init_once(void *foo)
INIT_LIST_HEAD(&nfsi->access_cache_entry_lru);
INIT_LIST_HEAD(&nfsi->access_cache_inode_lru);
INIT_LIST_HEAD(&nfsi->commit_info.list);
nfsi->npages = 0;
nfsi->nrequests = 0;
nfsi->commit_info.ncommit = 0;
atomic_set(&nfsi->commit_info.rpcs_out, 0);
atomic_set(&nfsi->silly_count, 1);

11
fs/nfs/pagelist.c
View File

@ -258,6 +258,7 @@ bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
static inline void
nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
{
struct inode *inode;
WARN_ON_ONCE(prev == req);
if (!prev) {
@ -276,12 +277,16 @@ nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
* nfs_page_group_destroy is called */
kref_get(&req->wb_head->wb_kref);
/* grab extra ref if head request has extra ref from
* the write/commit path to handle handoff between write
* and commit lists */
/* grab extra ref and bump the request count if head request
* has extra ref from the write/commit path to handle handoff
* between write and commit lists. */
if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
inode = page_file_mapping(req->wb_page)->host;
set_bit(PG_INODE_REF, &req->wb_flags);
kref_get(&req->wb_kref);
spin_lock(&inode->i_lock);
NFS_I(inode)->nrequests++;
spin_unlock(&inode->i_lock);
}
}
}

17
fs/nfs/write.c
View File

@ -670,7 +670,8 @@ static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
nfs_lock_request(req);
spin_lock(&inode->i_lock);
if (!nfsi->npages && NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
if (!nfsi->nrequests &&
NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
inode->i_version++;
/*
* Swap-space should not get truncated. Hence no need to plug the race
@ -681,9 +682,11 @@ static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
SetPagePrivate(req->wb_page);
set_page_private(req->wb_page, (unsigned long)req);
}
nfsi->npages++;
nfsi->nrequests++;
/* this a head request for a page group - mark it as having an
* extra reference so sub groups can follow suit */
* extra reference so sub groups can follow suit.
* This flag also informs pgio layer when to bump nrequests when
* adding subrequests. */
WARN_ON(test_and_set_bit(PG_INODE_REF, &req->wb_flags));
kref_get(&req->wb_kref);
spin_unlock(&inode->i_lock);
@ -709,7 +712,11 @@ static void nfs_inode_remove_request(struct nfs_page *req)
wake_up_page(head->wb_page, PG_private);
clear_bit(PG_MAPPED, &head->wb_flags);
}
nfsi->npages--;
nfsi->nrequests--;
spin_unlock(&inode->i_lock);
} else {
spin_lock(&inode->i_lock);
nfsi->nrequests--;
spin_unlock(&inode->i_lock);
}
@ -1735,7 +1742,7 @@ static int nfs_commit_unstable_pages(struct inode *inode, struct writeback_contr
/* Don't commit yet if this is a non-blocking flush and there
* are a lot of outstanding writes for this mapping.
*/
if (nfsi->commit_info.ncommit <= (nfsi->npages >> 1))
if (nfsi->commit_info.ncommit <= (nfsi->nrequests >> 1))
goto out_mark_dirty;
/* don't wait for the COMMIT response */

4
include/linux/nfs_fs.h
View File

@ -163,7 +163,7 @@ struct nfs_inode {
*/
__be32 cookieverf[2];
unsigned long npages;
unsigned long nrequests;
struct nfs_mds_commit_info commit_info;
/* Open contexts for shared mmap writes */
@ -520,7 +520,7 @@ extern void nfs_commit_free(struct nfs_commit_data *data);
static inline int
nfs_have_writebacks(struct inode *inode)
{
return NFS_I(inode)->npages != 0;
return NFS_I(inode)->nrequests != 0;
}
/*