[CIFS] Fix locking problem around some cifs uses of i_size write

Could cause hangs on smp systems in i_size_read on a cifs inode
whose size has been previously simultaneously updated from
different processes.

Thanks to Brian Wang for some great testing/debugging on this
hard problem.

Fixes kernel bugzilla #7903

CC: Shirish Pargoankar <shirishp@us.ibm.com>
CC: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 23 insertions, 20 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index a1265c9bfec0..c07ff8317a8b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -879,18 +879,19 @@ ssize_t cifs_user_write(struct file *file, const char __user *write_data,
         cifs_stats_bytes_written(pTcon, total_written);
 
         /* since the write may have blocked check these pointers again */
-        if (file->f_path.dentry) {
-                if (file->f_path.dentry->d_inode) {
-                        struct inode *inode = file->f_path.dentry->d_inode;
-                        inode->i_ctime = inode->i_mtime =
-                                current_fs_time(inode->i_sb);
-                        if (total_written > 0) {
-                                if (*poffset > file->f_path.dentry->d_inode->i_size)
-                                        i_size_write(file->f_path.dentry->d_inode,
+        if ((file->f_path.dentry) && (file->f_path.dentry->d_inode)) {
+                struct inode *inode = file->f_path.dentry->d_inode;
+/* Do not update local mtime - server will set its actual value on write                
+ *              inode->i_ctime = inode->i_mtime = 
+ *                      current_fs_time(inode->i_sb);*/
+                if (total_written > 0) {
+                        spin_lock(&inode->i_lock);
+                        if (*poffset > file->f_path.dentry->d_inode->i_size)
+                                i_size_write(file->f_path.dentry->d_inode,
                                         *poffset);
-                        }
-                        mark_inode_dirty_sync(file->f_path.dentry->d_inode);
+                        spin_unlock(&inode->i_lock);
                 }
+                mark_inode_dirty_sync(file->f_path.dentry->d_inode);    
         }
         FreeXid(xid);
         return total_written;
@@ -1012,18 +1013,18 @@ static ssize_t cifs_write(struct file *file, const char *write_data,
         cifs_stats_bytes_written(pTcon, total_written);
 
         /* since the write may have blocked check these pointers again */
-        if (file->f_path.dentry) {
-                if (file->f_path.dentry->d_inode) {
+        if ((file->f_path.dentry) && (file->f_path.dentry->d_inode)) {
 /*BB We could make this contingent on superblock ATIME flag too */
-/*                      file->f_path.dentry->d_inode->i_ctime =
-                        file->f_path.dentry->d_inode->i_mtime = CURRENT_TIME;*/
-                        if (total_written > 0) {
-                                if (*poffset > file->f_path.dentry->d_inode->i_size)
-                                        i_size_write(file->f_path.dentry->d_inode,
-                                                     *poffset);
-                        }
-                        mark_inode_dirty_sync(file->f_path.dentry->d_inode);
+/*              file->f_path.dentry->d_inode->i_ctime =
+                file->f_path.dentry->d_inode->i_mtime = CURRENT_TIME;*/
+                if (total_written > 0) {
+                        spin_lock(&file->f_path.dentry->d_inode->i_lock);
+                        if (*poffset > file->f_path.dentry->d_inode->i_size)
+                                i_size_write(file->f_path.dentry->d_inode,
+                                             *poffset);
+                        spin_unlock(&file->f_path.dentry->d_inode->i_lock);
                 }
+                mark_inode_dirty_sync(file->f_path.dentry->d_inode);
         }
         FreeXid(xid);
         return total_written;
@@ -1400,6 +1401,7 @@ static int cifs_commit_write(struct file *file, struct page *page,
         xid = GetXid();
         cFYI(1, ("commit write for page %p up to position %lld for %d", 
                  page, position, to));
+        spin_lock(&inode->i_lock);
         if (position > inode->i_size) {
                 i_size_write(inode, position);
                 /* if (file->private_data == NULL) {
@@ -1429,6 +1431,7 @@ static int cifs_commit_write(struct file *file, struct page *page,
                         cFYI(1, (" SetEOF (commit write) rc = %d", rc));
                 } */
         }
+        spin_unlock(&inode->i_lock);
         if (!PageUptodate(page)) {
                 position =  ((loff_t)page->index << PAGE_CACHE_SHIFT) + offset;
                 /* can not rely on (or let) writepage write this data */