CIFS: Fix write after setting a read lock for read oplock files

If we have a read oplock and set a read lock in it, we can't write to the
locked area - so, filemap_fdatawrite may fail with a no information for a
userspace application even if we request a write to non-locked area. Fix
this by populating the page cache without marking affected pages dirty
after a successful write directly to the server.

Also remove CONFIG_CIFS_SMB2 ifdefs because it's suitable for both CIFS
and SMB2 protocols.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

3 files changed, 65 insertions, 31 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index c6e32f22fbd3..210f0af83fc4 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -229,6 +229,7 @@ cifs_alloc_inode(struct super_block *sb)
         cifs_set_oplock_level(cifs_inode, 0);
         cifs_inode->delete_pending = false;
         cifs_inode->invalid_mapping = false;
+        cifs_inode->leave_pages_clean = false;
         cifs_inode->vfs_inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
         cifs_inode->server_eof = 0;
         cifs_inode->uniqueid = 0;
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index dfab450a191e..aea1eec64911 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1030,6 +1030,7 @@ struct cifsInodeInfo {
         bool clientCanCacheAll;         /* read and writebehind oplock */
         bool delete_pending;            /* DELETE_ON_CLOSE is set */
         bool invalid_mapping;           /* pagecache is invalid */
+        bool leave_pages_clean; /* protected by i_mutex, not set pages dirty */
         unsigned long time;             /* jiffies of last update of inode */
         u64  server_eof;                /* current file size on server -- protected by i_lock */
         u64  uniqueid;                  /* server inode number */
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 1b322d041f1e..0a6677ba212b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2103,7 +2103,15 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
         } else {
                 rc = copied;
                 pos += copied;
-                set_page_dirty(page);
+                /*
+                 * When we use strict cache mode and cifs_strict_writev was run
+                 * with level II oplock (indicated by leave_pages_clean field of
+                 * CIFS_I(inode)), we can leave pages clean - cifs_strict_writev
+                 * sent the data to the server itself.
+                 */
+                if (!CIFS_I(inode)->leave_pages_clean ||
+                    !(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO))
+                        set_page_dirty(page);
         }
 
         if (rc > 0) {
@@ -2454,8 +2462,8 @@ ssize_t cifs_user_writev(struct kiocb *iocb, const struct iovec *iov,
 }
 
 static ssize_t
-cifs_writev(struct kiocb *iocb, const struct iovec *iov,
-            unsigned long nr_segs, loff_t pos)
+cifs_pagecache_writev(struct kiocb *iocb, const struct iovec *iov,
+                      unsigned long nr_segs, loff_t pos, bool cache_ex)
 {
         struct file *file = iocb->ki_filp;
         struct cifsFileInfo *cfile = (struct cifsFileInfo *)file->private_data;
@@ -2477,8 +2485,12 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
                                      server->vals->exclusive_lock_type, NULL,
                                      CIFS_WRITE_OP)) {
                 mutex_lock(&inode->i_mutex);
+                if (!cache_ex)
+                        cinode->leave_pages_clean = true;
                 rc = __generic_file_aio_write(iocb, iov, nr_segs,
-                                               &iocb->ki_pos);
+                                              &iocb->ki_pos);
+                if (!cache_ex)
+                        cinode->leave_pages_clean = false;
                 mutex_unlock(&inode->i_mutex);
         }
 
@@ -2505,42 +2517,62 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
         struct cifsFileInfo *cfile = (struct cifsFileInfo *)
                                                 iocb->ki_filp->private_data;
         struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
-
-#ifdef CONFIG_CIFS_SMB2
+        ssize_t written, written2;
         /*
-         * If we have an oplock for read and want to write a data to the file
-         * we need to store it in the page cache and then push it to the server
-         * to be sure the next read will get a valid data.
+         * We need to store clientCanCacheAll here to prevent race
+         * conditions - this value can be changed during an execution
+         * of generic_file_aio_write. For CIFS it can be changed from
+         * true to false only, but for SMB2 it can be changed both from
+         * true to false and vice versa. So, we can end up with a data
+         * stored in the cache, not marked dirty and not sent to the
+         * server if this value changes its state from false to true
+         * after cifs_write_end.
          */
-        if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
-                ssize_t written;
-                int rc;
-
-                written = generic_file_aio_write(iocb, iov, nr_segs, pos);
-                rc = filemap_fdatawrite(inode->i_mapping);
-                if (rc)
-                        return (ssize_t)rc;
+        bool cache_ex = cinode->clientCanCacheAll;
+        bool cache_read = cinode->clientCanCacheRead;
+        int rc;
+        loff_t saved_pos;
 
-                return written;
+        if (cache_ex) {
+                if (cap_unix(tcon->ses) &&
+                    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
+                    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
+                                                tcon->fsUnixInfo.Capability)))
+                        return generic_file_aio_write(iocb, iov, nr_segs, pos);
+                return cifs_pagecache_writev(iocb, iov, nr_segs, pos, cache_ex);
         }
-#endif
 
         /*
-         * For non-oplocked files in strict cache mode we need to write the data
-         * to the server exactly from the pos to pos+len-1 rather than flush all
-         * affected pages because it may cause a error with mandatory locks on
-         * these pages but not on the region from pos to ppos+len-1.
+         * For files without exclusive oplock in strict cache mode we need to
+         * write the data to the server exactly from the pos to pos+len-1 rather
+         * than flush all affected pages because it may cause a error with
+         * mandatory locks on these pages but not on the region from pos to
+         * ppos+len-1.
          */
+        written = cifs_user_writev(iocb, iov, nr_segs, pos);
+        if (!cache_read || written <= 0)
+                return written;
 
-        if (!cinode->clientCanCacheAll)
-                return cifs_user_writev(iocb, iov, nr_segs, pos);
-
+        saved_pos = iocb->ki_pos;
+        iocb->ki_pos = pos;
+        /* we have a read oplock - need to store a data in the page cache */
         if (cap_unix(tcon->ses) &&
-            (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
-            ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
-                return generic_file_aio_write(iocb, iov, nr_segs, pos);
-
-        return cifs_writev(iocb, iov, nr_segs, pos);
+            ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
+            (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
+                                        tcon->fsUnixInfo.Capability)))
+                written2 = generic_file_aio_write(iocb, iov, nr_segs, pos);
+        else
+                written2 = cifs_pagecache_writev(iocb, iov, nr_segs, pos,
+                                                 cache_ex);
+        /* errors occured during writing - invalidate the page cache */
+        if (written2 < 0) {
+                rc = cifs_invalidate_mapping(inode);
+                if (rc)
+                        written = (ssize_t)rc;
+                else
+                        iocb->ki_pos = saved_pos;
+        }
+        return written;
 }
 
 static struct cifs_readdata *