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NFS: Clean up nfs_update_request() 

Simplify the loop in nfs_update_request by moving into a separate function
the code that attempts to update an existing cached NFS write.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2008-06-13 12:12:32 -04:00
parent 396cee977f
commit e7d39069e3
1 changed files with 102 additions and 97 deletions
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199
fs/nfs/write.c
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@ -34,9 +34,6 @@
/*
* Local function declarations
*/
static struct nfs_page * nfs_update_request(struct nfs_open_context*,
struct page *,
unsigned int, unsigned int);
static void nfs_pageio_init_write(struct nfs_pageio_descriptor *desc,
struct inode *inode, int ioflags);
static void nfs_redirty_request(struct nfs_page *req);
@ -169,30 +166,6 @@ static void nfs_mark_uptodate(struct page *page, unsigned int base, unsigned int
SetPageUptodate(page);
}
static int nfs_writepage_setup(struct nfs_open_context *ctx, struct page *page,
unsigned int offset, unsigned int count)
{
struct nfs_page *req;
int ret;
for (;;) {
req = nfs_update_request(ctx, page, offset, count);
if (!IS_ERR(req))
break;
ret = PTR_ERR(req);
if (ret != -EBUSY)
return ret;
ret = nfs_wb_page(page->mapping->host, page);
if (ret != 0)
return ret;
}
/* Update file length */
nfs_grow_file(page, offset, count);
nfs_mark_uptodate(page, req->wb_pgbase, req->wb_bytes);
nfs_clear_page_tag_locked(req);
return 0;
}
static int wb_priority(struct writeback_control *wbc)
{
if (wbc->for_reclaim)
@ -356,11 +329,19 @@ int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
/*
* Insert a write request into an inode
*/
static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
{
struct nfs_inode *nfsi = NFS_I(inode);
int error;
error = radix_tree_preload(GFP_NOFS);
if (error != 0)
goto out;
/* Lock the request! */
nfs_lock_request_dontget(req);
spin_lock(&inode->i_lock);
error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);
BUG_ON(error);
if (!nfsi->npages) {
@ -374,6 +355,10 @@ static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
kref_get(&req->wb_kref);
radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index,
NFS_PAGE_TAG_LOCKED);
spin_unlock(&inode->i_lock);
radix_tree_preload_end();
out:
return error;
}
/*
@ -565,101 +550,121 @@ static inline int nfs_scan_commit(struct inode *inode, struct list_head *dst, pg
#endif
/*
* Try to update any existing write request, or create one if there is none.
* In order to match, the request's credentials must match those of
* the calling process.
* Search for an existing write request, and attempt to update
* it to reflect a new dirty region on a given page.
*
* Note: Should always be called with the Page Lock held!
* If the attempt fails, then the existing request is flushed out
* to disk.
*/
static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx,
struct page *page, unsigned int offset, unsigned int bytes)
static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
struct page *page,
unsigned int offset,
unsigned int bytes)
{
struct address_space *mapping = page->mapping;
struct inode *inode = mapping->host;
struct nfs_page *req, *new = NULL;
pgoff_t rqend, end;
struct nfs_page *req;
unsigned int rqend;
unsigned int end;
int error;
if (!PagePrivate(page))
return NULL;
end = offset + bytes;
spin_lock(&inode->i_lock);
for (;;) {
/* Loop over all inode entries and see if we find
* A request for the page we wish to update
*/
spin_lock(&inode->i_lock);
req = nfs_page_find_request_locked(page);
if (req) {
if (!nfs_set_page_tag_locked(req)) {
int error;
if (req == NULL)
goto out_unlock;
spin_unlock(&inode->i_lock);
error = nfs_wait_on_request(req);
nfs_release_request(req);
if (error < 0) {
if (new) {
radix_tree_preload_end();
nfs_release_request(new);
}
return ERR_PTR(error);
}
continue;
}
spin_unlock(&inode->i_lock);
if (new) {
radix_tree_preload_end();
nfs_release_request(new);
}
rqend = req->wb_offset + req->wb_bytes;
/*
* Tell the caller to flush out the request if
* the offsets are non-contiguous.
* Note: nfs_flush_incompatible() will already
* have flushed out requests having wrong owners.
*/
if (!nfs_dirty_request(req)
|| offset > rqend
|| end < req->wb_offset)
goto out_flushme;
if (nfs_set_page_tag_locked(req))
break;
}
if (new) {
nfs_lock_request_dontget(new);
nfs_inode_add_request(inode, new);
spin_unlock(&inode->i_lock);
radix_tree_preload_end();
req = new;
goto out;
}
/* The request is locked, so wait and then retry */
spin_unlock(&inode->i_lock);
new = nfs_create_request(ctx, inode, page, offset, bytes);
if (IS_ERR(new))
return new;
if (radix_tree_preload(GFP_NOFS)) {
nfs_release_request(new);
return ERR_PTR(-ENOMEM);
}
}
/* We have a request for our page.
* If the creds don't match, or the
* page addresses don't match,
* tell the caller to wait on the conflicting
* request.
*/
rqend = req->wb_offset + req->wb_bytes;
if (req->wb_context != ctx
|| req->wb_page != page
|| !nfs_dirty_request(req)
|| offset > rqend || end < req->wb_offset) {
nfs_clear_page_tag_locked(req);
return ERR_PTR(-EBUSY);
error = nfs_wait_on_request(req);
nfs_release_request(req);
if (error != 0)
goto out_err;
spin_lock(&inode->i_lock);
}
/* Okay, the request matches. Update the region */
if (offset < req->wb_offset) {
req->wb_offset = offset;
req->wb_pgbase = offset;
req->wb_bytes = max(end, rqend) - req->wb_offset;
goto out;
}
if (end > rqend)
req->wb_bytes = end - req->wb_offset;
else
req->wb_bytes = rqend - req->wb_offset;
out_unlock:
spin_unlock(&inode->i_lock);
return req;
out_flushme:
spin_unlock(&inode->i_lock);
nfs_release_request(req);
error = nfs_wb_page(inode, page);
out_err:
return ERR_PTR(error);
}
/*
* Try to update an existing write request, or create one if there is none.
*
* Note: Should always be called with the Page Lock held to prevent races
* if we have to add a new request. Also assumes that the caller has
* already called nfs_flush_incompatible() if necessary.
*/
static struct nfs_page * nfs_setup_write_request(struct nfs_open_context* ctx,
struct page *page, unsigned int offset, unsigned int bytes)
{
struct inode *inode = page->mapping->host;
struct nfs_page *req;
int error;
req = nfs_try_to_update_request(inode, page, offset, bytes);
if (req != NULL)
goto out;
req = nfs_create_request(ctx, inode, page, offset, bytes);
if (IS_ERR(req))
goto out;
error = nfs_inode_add_request(inode, req);
if (error != 0) {
nfs_release_request(req);
req = ERR_PTR(error);
}
out:
return req;
}
static int nfs_writepage_setup(struct nfs_open_context *ctx, struct page *page,
unsigned int offset, unsigned int count)
{
struct nfs_page *req;
req = nfs_setup_write_request(ctx, page, offset, count);
if (IS_ERR(req))
return PTR_ERR(req);
/* Update file length */
nfs_grow_file(page, offset, count);
nfs_mark_uptodate(page, req->wb_pgbase, req->wb_bytes);
nfs_clear_page_tag_locked(req);
return 0;
}
int nfs_flush_incompatible(struct file *file, struct page *page)
{
struct nfs_open_context *ctx = nfs_file_open_context(file);