From 612aa983a041056c3368aacfdc9febd406d245a8 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 10 Sep 2014 08:23:30 -0700 Subject: pnfs: add flag to force read-modify-write in ->write_begin Like all block based filesystems, the pNFS block layout driver can't read or write at a byte granularity and thus has to perform read-modify-write cycles on writes smaller than this granularity. Add a flag so that the core NFS code always reads a whole page when starting a smaller write, so that we can do it in the place where the VFS expects it instead of doing in very deadlock prone way in the writeback handler. Note that in theory we could do less than page size reads here for disks that have a smaller sector size which are served by a server with a smaller pnfs block size. But so far that doesn't seem like a worthwhile optimization. Signed-off-by: Christoph Hellwig Signed-off-by: Trond Myklebust --- fs/nfs/file.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'fs/nfs/file.c') diff --git a/fs/nfs/file.c b/fs/nfs/file.c index 524dd80d1898..05ef7dcc5f21 100644 --- a/fs/nfs/file.c +++ b/fs/nfs/file.c @@ -36,6 +36,7 @@ #include "internal.h" #include "iostat.h" #include "fscache.h" +#include "pnfs.h" #include "nfstrace.h" @@ -327,6 +328,12 @@ static int nfs_want_read_modify_write(struct file *file, struct page *page, unsigned int offset = pos & (PAGE_CACHE_SIZE - 1); unsigned int end = offset + len; + if (pnfs_ld_read_whole_page(file->f_mapping->host)) { + if (!PageUptodate(page)) + return 1; + return 0; + } + if ((file->f_mode & FMODE_READ) && /* open for read? */ !PageUptodate(page) && /* Uptodate? */ !PagePrivate(page) && /* i/o request already? */ -- cgit v1.2.3