From 06cf6f2ed0b19629700794727d86ed57b9c0583e Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Tue, 20 Jun 2006 12:56:49 -0400 Subject: NFS: Eliminate nfs_get_user_pages() Neil Brown observed that the kmalloc() in nfs_get_user_pages() is more likely to fail if the I/O is large enough to require the allocation of more than a single page to keep track of all the pinned pages in the user's buffer. Instead of tracking one large page array per dreq/iocb, track pages per nfs_read/write_data, just like the cached I/O path does. An array for pages is already allocated for us by nfs_readdata_alloc() (and the write and commit equivalents). This is also required for adding support for vectored I/O to the NFS direct I/O path. The original reason to pin the user buffer and allocate all the NFS data structures before trying to schedule I/O was to ensure all needed resources are allocated on the client before starting to send requests. This reduces the chance that resource exhaustion on the client will cause a short read or write. On the other hand, for an application making very large application I/O requests, this means that it will be nearly impossible for the application to make forward progress on a resource-limited client. Thus, moving the buffer pinning functionality into the I/O scheduling loops should be good for scalability. The next patch will do the same for NFS data structure allocation. Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust --- include/linux/nfs_xdr.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h index 7c7320fa51aa..2d3fb6416d91 100644 --- a/include/linux/nfs_xdr.h +++ b/include/linux/nfs_xdr.h @@ -729,6 +729,7 @@ struct nfs_read_data { struct list_head pages; /* Coalesced read requests */ struct nfs_page *req; /* multi ops per nfs_page */ struct page **pagevec; + unsigned int npages; /* active pages in pagevec */ struct nfs_readargs args; struct nfs_readres res; #ifdef CONFIG_NFS_V4 @@ -747,6 +748,7 @@ struct nfs_write_data { struct list_head pages; /* Coalesced requests we wish to flush */ struct nfs_page *req; /* multi ops per nfs_page */ struct page **pagevec; + unsigned int npages; /* active pages in pagevec */ struct nfs_writeargs args; /* argument struct */ struct nfs_writeres res; /* result struct */ #ifdef CONFIG_NFS_V4 -- cgit v1.2.2