CIFS: implement cifs_writepages to perform multi-page I/O

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 184 insertions, 7 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 94875455d7fa..0473b221f643 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -21,11 +21,14 @@
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
 #include <linux/fs.h>
+#include <linux/backing-dev.h>
 #include <linux/stat.h>
 #include <linux/fcntl.h>
+#include <linux/mpage.h>
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 #include <linux/smp_lock.h>
+#include <linux/writeback.h>
 #include <asm/div64.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
@@ -916,6 +919,16 @@ static struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode)
                     ((open_file->pfile->f_flags & O_RDWR) ||
                      (open_file->pfile->f_flags & O_WRONLY))) {
                         read_unlock(&GlobalSMBSeslock);
+                        if(open_file->invalidHandle) {
+                                rc = cifs_reopen_file(cifs_inode->vfs_inode, 
+                                                      open_file->pfile, FALSE);
+                                /* if it fails, try another handle - might be */
+                                /* dangerous to hold up writepages with retry */
+                                if(rc) {
+                                        read_lock(&GlobalSMBSeslock);
+                                        continue;
+                                }
+                        }
                         return open_file;
                 }
         }
@@ -982,20 +995,181 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
         return rc;
 }
 
-#if 0
+#ifdef CONFIG_CIFS_EXPERIMENTAL
 static int cifs_writepages(struct address_space *mapping,
-        struct writeback_control *wbc)
+                           struct writeback_control *wbc)
 {
-        int rc = -EFAULT;
+        struct backing_dev_info *bdi = mapping->backing_dev_info;
+        unsigned int bytes_to_write;
+        unsigned int bytes_written;
+        struct cifs_sb_info *cifs_sb;
+        int done = 0;
+        pgoff_t end = -1;
+        pgoff_t index;
+        int is_range = 0;
+        struct kvec iov[32];
+        int n_iov = 0;
+        pgoff_t next;
+        int nr_pages;
+        __u64 offset = 0;
+        struct cifsFileInfo *open_file = NULL;
+        struct page *page;
+        struct pagevec pvec;
+        int rc = 0;
+        int scanned = 0;
         int xid;
 
+        cifs_sb = CIFS_SB(mapping->host->i_sb);
+        
+        /*
+         * If wsize is smaller that the page cache size, default to writing
+         * one page at a time via cifs_writepage
+         */
+        if (cifs_sb->wsize < PAGE_CACHE_SIZE)
+                return generic_writepages(mapping, wbc);
+
+        /*
+         * BB: Is this meaningful for a non-block-device file system?
+         * If it is, we should test it again after we do I/O
+         */
+        if (wbc->nonblocking && bdi_write_congested(bdi)) {
+                wbc->encountered_congestion = 1;
+                return 0;
+        }
+
         xid = GetXid();
 
-        /* Find contiguous pages then iterate through repeating
-           call 16K write then Setpageuptodate or if LARGE_WRITE_X
-           support then send larger writes via kevec so as to eliminate
-           a memcpy */
+        pagevec_init(&pvec, 0);
+        if (wbc->sync_mode == WB_SYNC_NONE)
+                index = mapping->writeback_index; /* Start from prev offset */
+        else {
+                index = 0;
+                scanned = 1;
+        }
+        if (wbc->start || wbc->end) {
+                index = wbc->start >> PAGE_CACHE_SHIFT;
+                end = wbc->end >> PAGE_CACHE_SHIFT;
+                is_range = 1;
+                scanned = 1;
+        }
+retry:
+        while (!done && (index <= end) &&
+               (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+                        PAGECACHE_TAG_DIRTY,
+                        min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1))) {
+                int first;
+                unsigned int i;
+
+                if (!open_file) {
+                        open_file = find_writable_file(CIFS_I(mapping->host));
+                        if (!open_file) {
+                                pagevec_release(&pvec);
+                                cERROR(1, ("No writable handles for inode"));
+                                return -EIO;
+                        }
+                }
+
+                first = -1;
+                next = 0;
+                n_iov = 0;
+                bytes_to_write = 0;
+
+                for (i = 0; i < nr_pages; i++) {
+                        page = pvec.pages[i];
+                        /*
+                         * At this point we hold neither mapping->tree_lock nor
+                         * lock on the page itself: the page may be truncated or
+                         * invalidated (changing page->mapping to NULL), or even
+                         * swizzled back from swapper_space to tmpfs file
+                         * mapping
+                         */
+
+                        if (first < 0)
+                                lock_page(page);
+                        else if (TestSetPageLocked(page))
+                                break;
+
+                        if (unlikely(page->mapping != mapping)) {
+                                unlock_page(page);
+                                break;
+                        }
+
+                        if (unlikely(is_range) && (page->index > end)) {
+                                done = 1;
+                                unlock_page(page);
+                                break;
+                        }
+
+                        if (next && (page->index != next)) {
+                                /* Not next consecutive page */
+                                unlock_page(page);
+                                break;
+                        }
+
+                        if (wbc->sync_mode != WB_SYNC_NONE)
+                                wait_on_page_writeback(page);
+
+                        if (PageWriteback(page) ||
+                                        !test_clear_page_dirty(page)) {
+                                unlock_page(page);
+                                break;
+                        }
+                        /*
+                         * BB can we get rid of this?  pages are held by pvec
+                         */
+                        page_cache_get(page);
+
+                        /* reserve iov[0] for the smb header */
+                        n_iov++;
+                        iov[n_iov].iov_base = kmap(page);
+                        iov[n_iov].iov_len = PAGE_CACHE_SIZE;
+                        bytes_to_write += PAGE_CACHE_SIZE;
+
+                        if (first < 0) {
+                                first = i;
+                                offset = page_offset(page);
+                        }
+                        next = page->index + 1;
+                        if (bytes_to_write + PAGE_CACHE_SIZE > cifs_sb->wsize)
+                                break;
+                }
+                if (n_iov) {
+                        rc = CIFSSMBWrite2(xid, cifs_sb->tcon,
+                                           open_file->netfid, bytes_to_write,
+                                           offset, &bytes_written, iov, n_iov,
+                                           1);
+                        if (rc || bytes_written < bytes_to_write) {
+                                cERROR(1,("CIFSSMBWrite2 returned %d, written = %x",
+                                          rc, bytes_written));
+                                set_bit(AS_EIO, &mapping->flags);
+                                SetPageError(page);
+                        }
+                        for (i = 0; i < n_iov; i++) {
+                                page = pvec.pages[first + i];
+                                kunmap(page);
+                                unlock_page(page);
+                                page_cache_release(page);
+                        }
+                        if ((wbc->nr_to_write -= n_iov) <= 0)
+                                done = 1;
+                        index = next;
+                }
+                pagevec_release(&pvec);
+        }
+        if (!scanned && !done) {
+                /*
+                 * We hit the last page and there is more work to be done: wrap
+                 * back to the start of the file
+                 */
+                scanned = 1;
+                index = 0;
+                goto retry;
+        }
+        if (!is_range)
+                mapping->writeback_index = index;
+
         FreeXid(xid);
+
         return rc;
 }
 #endif
@@ -1635,6 +1809,9 @@ struct address_space_operations cifs_addr_ops = {
         .readpage = cifs_readpage,
         .readpages = cifs_readpages,
         .writepage = cifs_writepage,
+#ifdef CONFIG_CIFS_EXPERIMENTAL
+        .writepages = cifs_writepages,
+#endif
         .prepare_write = cifs_prepare_write,
         .commit_write = cifs_commit_write,
         .set_page_dirty = __set_page_dirty_nobuffers,