2008-06-16 19:34:39

by Myklebust, Trond

[permalink] [raw]
Subject: [PATCH 2/2] NFS: Allow redirtying of a completed unstable write.

Currently, if an unstable write completes, we cannot redirty the page in
order to reflect a new change in the page data until after we've sent a
COMMIT request.

This patch allows a page rewrite to proceed without the unnecessary COMMIT
step, putting it immediately back onto the dirty page list, undoing the
VM unstable write accounting, and removing the NFS_PAGE_TAG_COMMIT tag from
the NFS radix tree.

Signed-off-by: Trond Myklebust <[email protected]>
---

fs/nfs/write.c | 67 +++++++++++++++++++++++-----------------------
include/linux/nfs_page.h | 9 ++++--
2 files changed, 39 insertions(+), 37 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index a675dc9..63cfe3f 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -270,12 +270,9 @@ static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
return ret;
spin_lock(&inode->i_lock);
}
- if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
- /* This request is marked for commit */
+ if (test_bit(PG_CLEAN, &req->wb_flags)) {
spin_unlock(&inode->i_lock);
- nfs_clear_page_tag_locked(req);
- nfs_pageio_complete(pgio);
- return 0;
+ BUG();
}
if (nfs_set_page_writeback(page) != 0) {
spin_unlock(&inode->i_lock);
@@ -407,19 +404,6 @@ nfs_mark_request_dirty(struct nfs_page *req)
__set_page_dirty_nobuffers(req->wb_page);
}

-/*
- * Check if a request is dirty
- */
-static inline int
-nfs_dirty_request(struct nfs_page *req)
-{
- struct page *page = req->wb_page;
-
- if (page == NULL || test_bit(PG_NEED_COMMIT, &req->wb_flags))
- return 0;
- return !PageWriteback(page);
-}
-
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
/*
* Add a request to the inode's commit list.
@@ -432,7 +416,7 @@ nfs_mark_request_commit(struct nfs_page *req)

spin_lock(&inode->i_lock);
nfsi->ncommit++;
- set_bit(PG_NEED_COMMIT, &(req)->wb_flags);
+ set_bit(PG_CLEAN, &(req)->wb_flags);
radix_tree_tag_set(&nfsi->nfs_page_tree,
req->wb_index,
NFS_PAGE_TAG_COMMIT);
@@ -442,6 +426,19 @@ nfs_mark_request_commit(struct nfs_page *req)
__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
}

+static int
+nfs_clear_request_commit(struct nfs_page *req)
+{
+ struct page *page = req->wb_page;
+
+ if (test_and_clear_bit(PG_CLEAN, &(req)->wb_flags)) {
+ dec_zone_page_state(page, NR_UNSTABLE_NFS);
+ dec_bdi_stat(page->mapping->backing_dev_info, BDI_RECLAIMABLE);
+ return 1;
+ }
+ return 0;
+}
+
static inline
int nfs_write_need_commit(struct nfs_write_data *data)
{
@@ -451,7 +448,7 @@ int nfs_write_need_commit(struct nfs_write_data *data)
static inline
int nfs_reschedule_unstable_write(struct nfs_page *req)
{
- if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
+ if (test_and_clear_bit(PG_NEED_COMMIT, &req->wb_flags)) {
nfs_mark_request_commit(req);
return 1;
}
@@ -467,6 +464,12 @@ nfs_mark_request_commit(struct nfs_page *req)
{
}

+static inline int
+nfs_clear_request_commit(struct nfs_page *req)
+{
+ return 0;
+}
+
static inline
int nfs_write_need_commit(struct nfs_write_data *data)
{
@@ -524,11 +527,8 @@ static void nfs_cancel_commit_list(struct list_head *head)

while(!list_empty(head)) {
req = nfs_list_entry(head->next);
- dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
- dec_bdi_stat(req->wb_page->mapping->backing_dev_info,
- BDI_RECLAIMABLE);
nfs_list_remove_request(req);
- clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);
+ nfs_clear_request_commit(req);
nfs_inode_remove_request(req);
nfs_unlock_request(req);
}
@@ -565,7 +565,7 @@ static inline int nfs_scan_commit(struct inode *inode, struct list_head *dst, pg
}
#endif

-static int nfs_try_to_update_request(struct nfs_page *req,
+static int nfs_try_to_update_request(struct inode *inode, struct nfs_page *req,
unsigned int offset,
unsigned int end)
{
@@ -579,7 +579,6 @@ static int nfs_try_to_update_request(struct nfs_page *req,
* wait on the conflicting request.
*/
if (req->wb_page == NULL
- || !nfs_dirty_request(req)
|| offset > rqend
|| end < req->wb_offset)
return -EBUSY;
@@ -587,6 +586,10 @@ static int nfs_try_to_update_request(struct nfs_page *req,
if (!nfs_set_page_tag_locked(req))
return -EAGAIN;

+ if (nfs_clear_request_commit(req))
+ radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
+ req->wb_index, NFS_PAGE_TAG_COMMIT);
+
/* Okay, the request matches. Update the region */
if (offset < req->wb_offset) {
req->wb_offset = offset;
@@ -623,7 +626,7 @@ static struct nfs_page * nfs_setup_write_request(struct nfs_open_context* ctx,
spin_lock(&inode->i_lock);
req = nfs_page_find_request_locked(page);
if (req) {
- error = nfs_try_to_update_request(req, offset, end);
+ error = nfs_try_to_update_request(inode, req, offset, end);
spin_unlock(&inode->i_lock);
if (error == 0)
break;
@@ -680,8 +683,7 @@ int nfs_flush_incompatible(struct file *file, struct page *page)
req = nfs_page_find_request(page);
if (req == NULL)
return 0;
- do_flush = req->wb_page != page || req->wb_context != ctx
- || !nfs_dirty_request(req);
+ do_flush = req->wb_page != page || req->wb_context != ctx;
nfs_release_request(req);
if (!do_flush)
return 0;
@@ -1286,10 +1288,7 @@ static void nfs_commit_release(void *calldata)
while (!list_empty(&data->pages)) {
req = nfs_list_entry(data->pages.next);
nfs_list_remove_request(req);
- clear_bit(PG_NEED_COMMIT, &(req)->wb_flags);
- dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
- dec_bdi_stat(req->wb_page->mapping->backing_dev_info,
- BDI_RECLAIMABLE);
+ nfs_clear_request_commit(req);

dprintk("NFS: commit (%s/%lld %[email protected]%lld)",
req->wb_context->path.dentry->d_inode->i_sb->s_id,
@@ -1465,7 +1464,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page)
req = nfs_page_find_request(page);
if (req == NULL)
goto out;
- if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
+ if (test_bit(PG_CLEAN, &req->wb_flags)) {
nfs_release_request(req);
break;
}
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index a1676e1..3c60685 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -27,9 +27,12 @@
/*
* Valid flags for a dirty buffer
*/
-#define PG_BUSY 0
-#define PG_NEED_COMMIT 1
-#define PG_NEED_RESCHED 2
+enum {
+ PG_BUSY = 0,
+ PG_CLEAN,
+ PG_NEED_COMMIT,
+ PG_NEED_RESCHED,
+};

struct nfs_inode;
struct nfs_page {