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NFS: Cleanup the coalescing code

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Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
2007-04-02 18:48:28 -04:00
parent 91e59c368c
commit d8a5ad75cc
4 changed files with 114 additions and 51 deletions
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117
fs/nfs/pagelist.c
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@@ -223,48 +223,101 @@ out:
}
/**
* nfs_coalesce_requests - Split coalesced requests out from a list.
* nfs_pageio_init - initialise a page io descriptor
* @desc: pointer to descriptor
* @iosize: io block size
*/
void nfs_pageio_init(struct nfs_pageio_descriptor *desc, unsigned int bsize)
{
INIT_LIST_HEAD(&desc->pg_list);
desc->pg_count = 0;
desc->pg_bsize = bsize;
desc->pg_base = 0;
}
/**
* nfs_can_coalesce_requests - test two requests for compatibility
* @prev: pointer to nfs_page
* @req: pointer to nfs_page
*
* The nfs_page structures 'prev' and 'req' are compared to ensure that the
* page data area they describe is contiguous, and that their RPC
* credentials, NFSv4 open state, and lockowners are the same.
*
* Return 'true' if this is the case, else return 'false'.
*/
static int nfs_can_coalesce_requests(struct nfs_page *prev,
struct nfs_page *req)
{
if (req->wb_context->cred != prev->wb_context->cred)
return 0;
if (req->wb_context->lockowner != prev->wb_context->lockowner)
return 0;
if (req->wb_context->state != prev->wb_context->state)
return 0;
if (req->wb_index != (prev->wb_index + 1))
return 0;
if (req->wb_pgbase != 0)
return 0;
if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
return 0;
return 1;
}
/**
* nfs_pageio_add_request - Attempt to coalesce a request into a page list.
* @desc: destination io descriptor
* @req: request
*
* Returns true if the request 'req' was successfully coalesced into the
* existing list of pages 'desc'.
*/
static int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
struct nfs_page *req)
{
size_t newlen = req->wb_bytes;
if (desc->pg_count != 0) {
struct nfs_page *prev;
/*
* FIXME: ideally we should be able to coalesce all requests
* that are not block boundary aligned, but currently this
* is problematic for the case of bsize < PAGE_CACHE_SIZE,
* since nfs_flush_multi and nfs_pagein_multi assume you
* can have only one struct nfs_page.
*/
newlen += desc->pg_count;
if (desc->pg_base + newlen > desc->pg_bsize)
return 0;
prev = nfs_list_entry(desc->pg_list.prev);
if (!nfs_can_coalesce_requests(prev, req))
return 0;
} else
desc->pg_base = req->wb_pgbase;
nfs_list_remove_request(req);
nfs_list_add_request(req, &desc->pg_list);
desc->pg_count = newlen;
return 1;
}
/**
* nfs_pageio_add_list - Split coalesced requests out from a list.
* @desc: destination io descriptor
* @head: source list
* @dst: destination list
* @nmax: maximum number of requests to coalesce
*
* Moves a maximum of 'nmax' elements from one list to another.
* The elements are checked to ensure that they form a contiguous set
* of pages, and that the RPC credentials are the same.
*/
int
nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
unsigned int nmax)
void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc,
struct list_head *head)
{
struct nfs_page *req = NULL;
unsigned int npages = 0;
while (!list_empty(head)) {
struct nfs_page *prev = req;
req = nfs_list_entry(head->next);
if (prev) {
if (req->wb_context->cred != prev->wb_context->cred)
break;
if (req->wb_context->lockowner != prev->wb_context->lockowner)
break;
if (req->wb_context->state != prev->wb_context->state)
break;
if (req->wb_index != (prev->wb_index + 1))
break;
if (req->wb_pgbase != 0)
break;
}
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
npages++;
if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
break;
if (npages >= nmax)
struct nfs_page *req = nfs_list_entry(head->next);
if (!nfs_pageio_add_request(desc, req))
break;
}
return npages;
}
#define NFS_SCAN_MAXENTRIES 16