Staging: aten2011: Clean up some tty bits
[safe/jmp/linux-2.6] / fs / cifs / file.c
index 1540ada..81747ac 100644 (file)
@@ -78,8 +78,36 @@ static inline int cifs_convert_flags(unsigned int flags)
        return (READ_CONTROL | FILE_WRITE_ATTRIBUTES | FILE_READ_ATTRIBUTES |
                FILE_WRITE_EA | FILE_APPEND_DATA | FILE_WRITE_DATA |
                FILE_READ_DATA);
+}
 
+static inline fmode_t cifs_posix_convert_flags(unsigned int flags)
+{
+       fmode_t posix_flags = 0;
 
+       if ((flags & O_ACCMODE) == O_RDONLY)
+               posix_flags = FMODE_READ;
+       else if ((flags & O_ACCMODE) == O_WRONLY)
+               posix_flags = FMODE_WRITE;
+       else if ((flags & O_ACCMODE) == O_RDWR) {
+               /* GENERIC_ALL is too much permission to request
+                  can cause unnecessary access denied on create */
+               /* return GENERIC_ALL; */
+               posix_flags = FMODE_READ | FMODE_WRITE;
+       }
+       /* can not map O_CREAT or O_EXCL or O_TRUNC flags when
+          reopening a file.  They had their effect on the original open */
+       if (flags & O_APPEND)
+               posix_flags |= (fmode_t)O_APPEND;
+       if (flags & O_SYNC)
+               posix_flags |= (fmode_t)O_SYNC;
+       if (flags & O_DIRECTORY)
+               posix_flags |= (fmode_t)O_DIRECTORY;
+       if (flags & O_NOFOLLOW)
+               posix_flags |= (fmode_t)O_NOFOLLOW;
+       if (flags & O_DIRECT)
+               posix_flags |= (fmode_t)O_DIRECT;
+
+       return posix_flags;
 }
 
 static inline int cifs_get_disposition(unsigned int flags)
@@ -97,6 +125,80 @@ static inline int cifs_get_disposition(unsigned int flags)
 }
 
 /* all arguments to this function must be checked for validity in caller */
+static inline int cifs_posix_open_inode_helper(struct inode *inode,
+                       struct file *file, struct cifsInodeInfo *pCifsInode,
+                       struct cifsFileInfo *pCifsFile, int oplock, u16 netfid)
+{
+       struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+/*     struct timespec temp; */   /* BB REMOVEME BB */
+
+       file->private_data = kmalloc(sizeof(struct cifsFileInfo), GFP_KERNEL);
+       if (file->private_data == NULL)
+               return -ENOMEM;
+       pCifsFile = cifs_init_private(file->private_data, inode, file, netfid);
+       write_lock(&GlobalSMBSeslock);
+       list_add(&pCifsFile->tlist, &cifs_sb->tcon->openFileList);
+
+       pCifsInode = CIFS_I(file->f_path.dentry->d_inode);
+       if (pCifsInode == NULL) {
+               write_unlock(&GlobalSMBSeslock);
+               return -EINVAL;
+       }
+
+       /* want handles we can use to read with first
+          in the list so we do not have to walk the
+          list to search for one in write_begin */
+       if ((file->f_flags & O_ACCMODE) == O_WRONLY) {
+               list_add_tail(&pCifsFile->flist,
+                             &pCifsInode->openFileList);
+       } else {
+               list_add(&pCifsFile->flist,
+                        &pCifsInode->openFileList);
+       }
+
+       if (pCifsInode->clientCanCacheRead) {
+               /* we have the inode open somewhere else
+                  no need to discard cache data */
+               goto psx_client_can_cache;
+       }
+
+       /* BB FIXME need to fix this check to move it earlier into posix_open
+          BB  fIX following section BB FIXME */
+
+       /* if not oplocked, invalidate inode pages if mtime or file
+          size changed */
+/*     temp = cifs_NTtimeToUnix(le64_to_cpu(buf->LastWriteTime));
+       if (timespec_equal(&file->f_path.dentry->d_inode->i_mtime, &temp) &&
+                          (file->f_path.dentry->d_inode->i_size ==
+                           (loff_t)le64_to_cpu(buf->EndOfFile))) {
+               cFYI(1, ("inode unchanged on server"));
+       } else {
+               if (file->f_path.dentry->d_inode->i_mapping) {
+                       rc = filemap_write_and_wait(file->f_path.dentry->d_inode->i_mapping);
+                       if (rc != 0)
+                               CIFS_I(file->f_path.dentry->d_inode)->write_behind_rc = rc;
+               }
+               cFYI(1, ("invalidating remote inode since open detected it "
+                        "changed"));
+               invalidate_remote_inode(file->f_path.dentry->d_inode);
+       } */
+
+psx_client_can_cache:
+       if ((oplock & 0xF) == OPLOCK_EXCLUSIVE) {
+               pCifsInode->clientCanCacheAll = true;
+               pCifsInode->clientCanCacheRead = true;
+               cFYI(1, ("Exclusive Oplock granted on inode %p",
+                        file->f_path.dentry->d_inode));
+       } else if ((oplock & 0xF) == OPLOCK_READ)
+               pCifsInode->clientCanCacheRead = true;
+
+       /* will have to change the unlock if we reenable the
+          filemap_fdatawrite (which does not seem necessary */
+       write_unlock(&GlobalSMBSeslock);
+       return 0;
+}
+
+/* all arguments to this function must be checked for validity in caller */
 static inline int cifs_open_inode_helper(struct inode *inode, struct file *file,
        struct cifsInodeInfo *pCifsInode, struct cifsFileInfo *pCifsFile,
        struct cifsTconInfo *pTcon, int *oplock, FILE_ALL_INFO *buf,
@@ -167,7 +269,7 @@ int cifs_open(struct inode *inode, struct file *file)
        int rc = -EACCES;
        int xid, oplock;
        struct cifs_sb_info *cifs_sb;
-       struct cifsTconInfo *pTcon;
+       struct cifsTconInfo *tcon;
        struct cifsFileInfo *pCifsFile;
        struct cifsInodeInfo *pCifsInode;
        struct list_head *tmp;
@@ -180,7 +282,7 @@ int cifs_open(struct inode *inode, struct file *file)
        xid = GetXid();
 
        cifs_sb = CIFS_SB(inode->i_sb);
-       pTcon = cifs_sb->tcon;
+       tcon = cifs_sb->tcon;
 
        if (file->f_flags & O_CREAT) {
                /* search inode for this file and fill in file->private_data */
@@ -220,6 +322,45 @@ int cifs_open(struct inode *inode, struct file *file)
 
        cFYI(1, ("inode = 0x%p file flags are 0x%x for %s",
                 inode, file->f_flags, full_path));
+
+       if (oplockEnabled)
+               oplock = REQ_OPLOCK;
+       else
+               oplock = 0;
+
+       if (!tcon->broken_posix_open && tcon->unix_ext &&
+           (tcon->ses->capabilities & CAP_UNIX) &&
+           (CIFS_UNIX_POSIX_PATH_OPS_CAP &
+                       le64_to_cpu(tcon->fsUnixInfo.Capability))) {
+               int oflags = (int) cifs_posix_convert_flags(file->f_flags);
+               /* can not refresh inode info since size could be stale */
+               rc = cifs_posix_open(full_path, &inode, inode->i_sb,
+                                    cifs_sb->mnt_file_mode /* ignored */,
+                                    oflags, &oplock, &netfid, xid);
+               if (rc == 0) {
+                       cFYI(1, ("posix open succeeded"));
+                       /* no need for special case handling of setting mode
+                          on read only files needed here */
+
+                       cifs_posix_open_inode_helper(inode, file, pCifsInode,
+                                                    pCifsFile, oplock, netfid);
+                       goto out;
+               } else if ((rc == -EINVAL) || (rc == -EOPNOTSUPP)) {
+                       if (tcon->ses->serverNOS)
+                               cERROR(1, ("server %s of type %s returned"
+                                          " unexpected error on SMB posix open"
+                                          ", disabling posix open support."
+                                          " Check if server update available.",
+                                          tcon->ses->serverName,
+                                          tcon->ses->serverNOS));
+                       tcon->broken_posix_open = true;
+               } else if ((rc != -EIO) && (rc != -EREMOTE) &&
+                        (rc != -EOPNOTSUPP)) /* path not found or net err */
+                       goto out;
+               /* else fallthrough to retry open the old way on network i/o
+                  or DFS errors */
+       }
+
        desiredAccess = cifs_convert_flags(file->f_flags);
 
 /*********************************************************************
@@ -248,11 +389,6 @@ int cifs_open(struct inode *inode, struct file *file)
 
        disposition = cifs_get_disposition(file->f_flags);
 
-       if (oplockEnabled)
-               oplock = REQ_OPLOCK;
-       else
-               oplock = 0;
-
        /* BB pass O_SYNC flag through on file attributes .. BB */
 
        /* Also refresh inode by passing in file_info buf returned by SMBOpen
@@ -269,7 +405,7 @@ int cifs_open(struct inode *inode, struct file *file)
        }
 
        if (cifs_sb->tcon->ses->capabilities & CAP_NT_SMBS)
-               rc = CIFSSMBOpen(xid, pTcon, full_path, disposition,
+               rc = CIFSSMBOpen(xid, tcon, full_path, disposition,
                         desiredAccess, CREATE_NOT_DIR, &netfid, &oplock, buf,
                         cifs_sb->local_nls, cifs_sb->mnt_cifs_flags
                                 & CIFS_MOUNT_MAP_SPECIAL_CHR);
@@ -278,7 +414,7 @@ int cifs_open(struct inode *inode, struct file *file)
 
        if (rc == -EIO) {
                /* Old server, try legacy style OpenX */
-               rc = SMBLegacyOpen(xid, pTcon, full_path, disposition,
+               rc = SMBLegacyOpen(xid, tcon, full_path, disposition,
                        desiredAccess, CREATE_NOT_DIR, &netfid, &oplock, buf,
                        cifs_sb->local_nls, cifs_sb->mnt_cifs_flags
                                & CIFS_MOUNT_MAP_SPECIAL_CHR);
@@ -295,12 +431,12 @@ int cifs_open(struct inode *inode, struct file *file)
        }
        pCifsFile = cifs_init_private(file->private_data, inode, file, netfid);
        write_lock(&GlobalSMBSeslock);
-       list_add(&pCifsFile->tlist, &pTcon->openFileList);
+       list_add(&pCifsFile->tlist, &tcon->openFileList);
 
        pCifsInode = CIFS_I(file->f_path.dentry->d_inode);
        if (pCifsInode) {
                rc = cifs_open_inode_helper(inode, file, pCifsInode,
-                                           pCifsFile, pTcon,
+                                           pCifsFile, tcon,
                                            &oplock, buf, full_path, xid);
        } else {
                write_unlock(&GlobalSMBSeslock);
@@ -309,7 +445,7 @@ int cifs_open(struct inode *inode, struct file *file)
        if (oplock & CIFS_CREATE_ACTION) {
                /* time to set mode which we can not set earlier due to
                   problems creating new read-only files */
-               if (pTcon->unix_ext) {
+               if (tcon->unix_ext) {
                        struct cifs_unix_set_info_args args = {
                                .mode   = inode->i_mode,
                                .uid    = NO_CHANGE_64,
@@ -319,7 +455,7 @@ int cifs_open(struct inode *inode, struct file *file)
                                .mtime  = NO_CHANGE_64,
                                .device = 0,
                        };
-                       CIFSSMBUnixSetInfo(xid, pTcon, full_path, &args,
+                       CIFSSMBUnixSetInfo(xid, tcon, full_path, &args,
                                            cifs_sb->local_nls,
                                            cifs_sb->mnt_cifs_flags &
                                                CIFS_MOUNT_MAP_SPECIAL_CHR);
@@ -349,7 +485,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
        int rc = -EACCES;
        int xid, oplock;
        struct cifs_sb_info *cifs_sb;
-       struct cifsTconInfo *pTcon;
+       struct cifsTconInfo *tcon;
        struct cifsFileInfo *pCifsFile;
        struct cifsInodeInfo *pCifsInode;
        struct inode *inode;
@@ -387,7 +523,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
        }
 
        cifs_sb = CIFS_SB(inode->i_sb);
-       pTcon = cifs_sb->tcon;
+       tcon = cifs_sb->tcon;
 
 /* can not grab rename sem here because various ops, including
    those that already have the rename sem can end up causing writepage
@@ -404,20 +540,37 @@ reopen_error_exit:
 
        cFYI(1, ("inode = 0x%p file flags 0x%x for %s",
                 inode, file->f_flags, full_path));
-       desiredAccess = cifs_convert_flags(file->f_flags);
 
        if (oplockEnabled)
                oplock = REQ_OPLOCK;
        else
                oplock = 0;
 
+       if (tcon->unix_ext && (tcon->ses->capabilities & CAP_UNIX) &&
+           (CIFS_UNIX_POSIX_PATH_OPS_CAP &
+                       le64_to_cpu(tcon->fsUnixInfo.Capability))) {
+               int oflags = (int) cifs_posix_convert_flags(file->f_flags);
+               /* can not refresh inode info since size could be stale */
+               rc = cifs_posix_open(full_path, NULL, inode->i_sb,
+                                    cifs_sb->mnt_file_mode /* ignored */,
+                                    oflags, &oplock, &netfid, xid);
+               if (rc == 0) {
+                       cFYI(1, ("posix reopen succeeded"));
+                       goto reopen_success;
+               }
+               /* fallthrough to retry open the old way on errors, especially
+                  in the reconnect path it is important to retry hard */
+       }
+
+       desiredAccess = cifs_convert_flags(file->f_flags);
+
        /* Can not refresh inode by passing in file_info buf to be returned
           by SMBOpen and then calling get_inode_info with returned buf
           since file might have write behind data that needs to be flushed
           and server version of file size can be stale. If we knew for sure
           that inode was not dirty locally we could do this */
 
-       rc = CIFSSMBOpen(xid, pTcon, full_path, disposition, desiredAccess,
+       rc = CIFSSMBOpen(xid, tcon, full_path, disposition, desiredAccess,
                         CREATE_NOT_DIR, &netfid, &oplock, NULL,
                         cifs_sb->local_nls, cifs_sb->mnt_cifs_flags &
                                CIFS_MOUNT_MAP_SPECIAL_CHR);
@@ -426,6 +579,7 @@ reopen_error_exit:
                cFYI(1, ("cifs_open returned 0x%x", rc));
                cFYI(1, ("oplock: %d", oplock));
        } else {
+reopen_success:
                pCifsFile->netfid = netfid;
                pCifsFile->invalidHandle = false;
                up(&pCifsFile->fh_sem);
@@ -439,7 +593,7 @@ reopen_error_exit:
                           go to server to get inode info */
                                pCifsInode->clientCanCacheAll = false;
                                pCifsInode->clientCanCacheRead = false;
-                               if (pTcon->unix_ext)
+                               if (tcon->unix_ext)
                                        rc = cifs_get_inode_info_unix(&inode,
                                                full_path, inode->i_sb, xid);
                                else
@@ -467,7 +621,6 @@ reopen_error_exit:
                        cifs_relock_file(pCifsFile);
                }
        }
-
        kfree(full_path);
        FreeXid(xid);
        return rc;
@@ -488,12 +641,13 @@ int cifs_close(struct inode *inode, struct file *file)
        pTcon = cifs_sb->tcon;
        if (pSMBFile) {
                struct cifsLockInfo *li, *tmp;
-
+               write_lock(&GlobalSMBSeslock);
                pSMBFile->closePend = true;
                if (pTcon) {
                        /* no sense reconnecting to close a file that is
                           already closed */
                        if (!pTcon->need_reconnect) {
+                               write_unlock(&GlobalSMBSeslock);
                                timeout = 2;
                                while ((atomic_read(&pSMBFile->wrtPending) != 0)
                                        && (timeout <= 2048)) {
@@ -510,12 +664,15 @@ int cifs_close(struct inode *inode, struct file *file)
                                        timeout *= 4;
                                }
                                if (atomic_read(&pSMBFile->wrtPending))
-                                       cERROR(1,
-                                               ("close with pending writes"));
-                               rc = CIFSSMBClose(xid, pTcon,
+                                       cERROR(1, ("close with pending write"));
+                               if (!pTcon->need_reconnect &&
+                                   !pSMBFile->invalidHandle)
+                                       rc = CIFSSMBClose(xid, pTcon,
                                                  pSMBFile->netfid);
-                       }
-               }
+                       } else
+                               write_unlock(&GlobalSMBSeslock);
+               } else
+                       write_unlock(&GlobalSMBSeslock);
 
                /* Delete any outstanding lock records.
                   We'll lose them when the file is closed anyway. */
@@ -587,15 +744,18 @@ int cifs_closedir(struct inode *inode, struct file *file)
                pTcon = cifs_sb->tcon;
 
                cFYI(1, ("Freeing private data in close dir"));
+               write_lock(&GlobalSMBSeslock);
                if (!pCFileStruct->srch_inf.endOfSearch &&
                    !pCFileStruct->invalidHandle) {
                        pCFileStruct->invalidHandle = true;
+                       write_unlock(&GlobalSMBSeslock);
                        rc = CIFSFindClose(xid, pTcon, pCFileStruct->netfid);
                        cFYI(1, ("Closing uncompleted readdir with rc %d",
                                 rc));
                        /* not much we can do if it fails anyway, ignore rc */
                        rc = 0;
-               }
+               } else
+                       write_unlock(&GlobalSMBSeslock);
                ptmp = pCFileStruct->srch_inf.ntwrk_buf_start;
                if (ptmp) {
                        cFYI(1, ("closedir free smb buf in srch struct"));
@@ -637,10 +797,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
        __u64 length;
        bool wait_flag = false;
        struct cifs_sb_info *cifs_sb;
-       struct cifsTconInfo *pTcon;
+       struct cifsTconInfo *tcon;
        __u16 netfid;
        __u8 lockType = LOCKING_ANDX_LARGE_FILES;
-       bool posix_locking;
+       bool posix_locking = 0;
 
        length = 1 + pfLock->fl_end - pfLock->fl_start;
        rc = -EACCES;
@@ -691,7 +851,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                cFYI(1, ("Unknown type of lock"));
 
        cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
-       pTcon = cifs_sb->tcon;
+       tcon = cifs_sb->tcon;
 
        if (file->private_data == NULL) {
                FreeXid(xid);
@@ -699,9 +859,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
        }
        netfid = ((struct cifsFileInfo *)file->private_data)->netfid;
 
-       posix_locking = (cifs_sb->tcon->ses->capabilities & CAP_UNIX) &&
-                       (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(cifs_sb->tcon->fsUnixInfo.Capability));
-
+       if ((tcon->ses->capabilities & CAP_UNIX) &&
+           (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
+           ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
+               posix_locking = 1;
        /* BB add code here to normalize offset and length to
        account for negative length which we can not accept over the
        wire */
@@ -712,7 +873,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                                posix_lock_type = CIFS_RDLCK;
                        else
                                posix_lock_type = CIFS_WRLCK;
-                       rc = CIFSSMBPosixLock(xid, pTcon, netfid, 1 /* get */,
+                       rc = CIFSSMBPosixLock(xid, tcon, netfid, 1 /* get */,
                                        length, pfLock,
                                        posix_lock_type, wait_flag);
                        FreeXid(xid);
@@ -720,10 +881,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                }
 
                /* BB we could chain these into one lock request BB */
-               rc = CIFSSMBLock(xid, pTcon, netfid, length, pfLock->fl_start,
+               rc = CIFSSMBLock(xid, tcon, netfid, length, pfLock->fl_start,
                                 0, 1, lockType, 0 /* wait flag */ );
                if (rc == 0) {
-                       rc = CIFSSMBLock(xid, pTcon, netfid, length,
+                       rc = CIFSSMBLock(xid, tcon, netfid, length,
                                         pfLock->fl_start, 1 /* numUnlock */ ,
                                         0 /* numLock */ , lockType,
                                         0 /* wait flag */ );
@@ -760,7 +921,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                if (numUnlock == 1)
                        posix_lock_type = CIFS_UNLCK;
 
-               rc = CIFSSMBPosixLock(xid, pTcon, netfid, 0 /* set */,
+               rc = CIFSSMBPosixLock(xid, tcon, netfid, 0 /* set */,
                                      length, pfLock,
                                      posix_lock_type, wait_flag);
        } else {
@@ -768,7 +929,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                        (struct cifsFileInfo *)file->private_data;
 
                if (numLock) {
-                       rc = CIFSSMBLock(xid, pTcon, netfid, length,
+                       rc = CIFSSMBLock(xid, tcon, netfid, length,
                                        pfLock->fl_start,
                                        0, numLock, lockType, wait_flag);
 
@@ -789,7 +950,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                                if (pfLock->fl_start <= li->offset &&
                                                (pfLock->fl_start + length) >=
                                                (li->offset + li->length)) {
-                                       stored_rc = CIFSSMBLock(xid, pTcon,
+                                       stored_rc = CIFSSMBLock(xid, tcon,
                                                        netfid,
                                                        li->length, li->offset,
                                                        1, 0, li->type, false);
@@ -1404,7 +1565,10 @@ retry:
                        if ((wbc->nr_to_write -= n_iov) <= 0)
                                done = 1;
                        index = next;
-               }
+               } else
+                       /* Need to re-find the pages we skipped */
+                       index = pvec.pages[0]->index + 1;
+
                pagevec_release(&pvec);
        }
        if (!scanned && !done) {
@@ -1465,7 +1629,11 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
        cFYI(1, ("write_end for page %p from pos %lld with %d bytes",
                 page, pos, copied));
 
-       if (!PageUptodate(page) && copied == PAGE_CACHE_SIZE)
+       if (PageChecked(page)) {
+               if (copied == len)
+                       SetPageUptodate(page);
+               ClearPageChecked(page);
+       } else if (!PageUptodate(page) && copied == PAGE_CACHE_SIZE)
                SetPageUptodate(page);
 
        if (!PageUptodate(page)) {
@@ -1508,6 +1676,9 @@ int cifs_fsync(struct file *file, struct dentry *dentry, int datasync)
 {
        int xid;
        int rc = 0;
+       struct cifsTconInfo *tcon;
+       struct cifsFileInfo *smbfile =
+               (struct cifsFileInfo *)file->private_data;
        struct inode *inode = file->f_path.dentry->d_inode;
 
        xid = GetXid();
@@ -1519,7 +1690,12 @@ int cifs_fsync(struct file *file, struct dentry *dentry, int datasync)
        if (rc == 0) {
                rc = CIFS_I(inode)->write_behind_rc;
                CIFS_I(inode)->write_behind_rc = 0;
+               tcon = CIFS_SB(inode->i_sb)->tcon;
+               if (!rc && tcon && smbfile &&
+                  !(CIFS_SB(inode->i_sb)->mnt_cifs_flags & CIFS_MOUNT_NOSSYNC))
+                       rc = CIFSSMBFlush(xid, tcon, smbfile->netfid);
        }
+
        FreeXid(xid);
        return rc;
 }
@@ -2052,39 +2228,70 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 {
        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
        loff_t offset = pos & (PAGE_CACHE_SIZE - 1);
+       loff_t page_start = pos & PAGE_MASK;
+       loff_t i_size;
+       struct page *page;
+       int rc = 0;
 
        cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));
 
-       *pagep = __grab_cache_page(mapping, index);
-       if (!*pagep)
-               return -ENOMEM;
-
-       if (PageUptodate(*pagep))
-               return 0;
+       page = grab_cache_page_write_begin(mapping, index, flags);
+       if (!page) {
+               rc = -ENOMEM;
+               goto out;
+       }
 
-       /* If we are writing a full page it will be up to date,
-          no need to read from the server */
-       if (len == PAGE_CACHE_SIZE && flags & AOP_FLAG_UNINTERRUPTIBLE)
-               return 0;
+       if (PageUptodate(page))
+               goto out;
 
-       if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
-               int rc;
+       /*
+        * If we write a full page it will be up to date, no need to read from
+        * the server. If the write is short, we'll end up doing a sync write
+        * instead.
+        */
+       if (len == PAGE_CACHE_SIZE)
+               goto out;
 
-               /* might as well read a page, it is fast enough */
-               rc = cifs_readpage_worker(file, *pagep, &offset);
+       /*
+        * optimize away the read when we have an oplock, and we're not
+        * expecting to use any of the data we'd be reading in. That
+        * is, when the page lies beyond the EOF, or straddles the EOF
+        * and the write will cover all of the existing data.
+        */
+       if (CIFS_I(mapping->host)->clientCanCacheRead) {
+               i_size = i_size_read(mapping->host);
+               if (page_start >= i_size ||
+                   (offset == 0 && (pos + len) >= i_size)) {
+                       zero_user_segments(page, 0, offset,
+                                          offset + len,
+                                          PAGE_CACHE_SIZE);
+                       /*
+                        * PageChecked means that the parts of the page
+                        * to which we're not writing are considered up
+                        * to date. Once the data is copied to the
+                        * page, it can be set uptodate.
+                        */
+                       SetPageChecked(page);
+                       goto out;
+               }
+       }
 
-               /* we do not need to pass errors back
-                  e.g. if we do not have read access to the file
-                  because cifs_write_end will attempt synchronous writes
-                  -- shaggy */
+       if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
+               /*
+                * might as well read a page, it is fast enough. If we get
+                * an error, we don't need to return it. cifs_write_end will
+                * do a sync write instead since PG_uptodate isn't set.
+                */
+               cifs_readpage_worker(file, page, &page_start);
        } else {
                /* we could try using another file handle if there is one -
                   but how would we lock it to prevent close of that handle
                   racing with this read? In any case
                   this will be written out by write_end so is fine */
        }
-
-       return 0;
+out:
+       *pagep = page;
+       return rc;
 }
 
 const struct address_space_operations cifs_addr_ops = {