4 files changed, 254 insertions, 56 deletions

diff --git a/fs/attr.c b/fs/attr.c
index 0815e93bb487..b4fa3b0aa596 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -67,14 +67,14 @@ EXPORT_SYMBOL(inode_change_ok);
  * @offset:     the new size to assign to the inode
  * @Returns:    0 on success, -ve errno on failure
  *
+ * inode_newsize_ok must be called with i_mutex held.
+ *
  * inode_newsize_ok will check filesystem limits and ulimits to check that the
  * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
  * when necessary. Caller must not proceed with inode size change if failure is
  * returned. @inode must be a file (not directory), with appropriate
  * permissions to allow truncate (inode_newsize_ok does NOT check these
  * conditions).
- *
- * inode_newsize_ok must be called with i_mutex held.
  */
 int inode_newsize_ok(const struct inode *inode, loff_t offset)
 {
@@ -104,17 +104,25 @@ out_big:
 }
 EXPORT_SYMBOL(inode_newsize_ok);
 
-int inode_setattr(struct inode * inode, struct iattr * attr)
+/**
+ * generic_setattr - copy simple metadata updates into the generic inode
+ * @inode:      the inode to be updated
+ * @attr:       the new attributes
+ *
+ * generic_setattr must be called with i_mutex held.
+ *
+ * generic_setattr updates the inode's metadata with that specified
+ * in attr. Noticably missing is inode size update, which is more complex
+ * as it requires pagecache updates. See simple_setsize.
+ *
+ * The inode is not marked as dirty after this operation. The rationale is
+ * that for "simple" filesystems, the struct inode is the inode storage.
+ * The caller is free to mark the inode dirty afterwards if needed.
+ */
+void generic_setattr(struct inode *inode, const struct iattr *attr)
 {
         unsigned int ia_valid = attr->ia_valid;
 
-        if (ia_valid & ATTR_SIZE &&
-            attr->ia_size != i_size_read(inode)) {
-                int error = vmtruncate(inode, attr->ia_size);
-                if (error)
-                        return error;
-        }
-
         if (ia_valid & ATTR_UID)
                 inode->i_uid = attr->ia_uid;
         if (ia_valid & ATTR_GID)
@@ -135,6 +143,28 @@ int inode_setattr(struct inode * inode, struct iattr * attr)
                         mode &= ~S_ISGID;
                 inode->i_mode = mode;
         }
+}
+EXPORT_SYMBOL(generic_setattr);
+
+/*
+ * note this function is deprecated, the new truncate sequence should be
+ * used instead -- see eg. simple_setsize, generic_setattr.
+ */
+int inode_setattr(struct inode *inode, const struct iattr *attr)
+{
+        unsigned int ia_valid = attr->ia_valid;
+
+        if (ia_valid & ATTR_SIZE &&
+            attr->ia_size != i_size_read(inode)) {
+                int error;
+
+                error = vmtruncate(inode, attr->ia_size);
+                if (error)
+                        return error;
+        }
+
+        generic_setattr(inode, attr);
+
         mark_inode_dirty(inode);
 
         return 0;
diff --git a/fs/buffer.c b/fs/buffer.c
index e8aa7081d25c..d54812b198e9 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1949,14 +1949,11 @@ static int __block_commit_write(struct inode *inode, struct page *page,
 }
 
 /*
- * block_write_begin takes care of the basic task of block allocation and
- * bringing partial write blocks uptodate first.
- *
- * If *pagep is not NULL, then block_write_begin uses the locked page
- * at *pagep rather than allocating its own. In this case, the page will
- * not be unlocked or deallocated on failure.
+ * Filesystems implementing the new truncate sequence should use the
+ * _newtrunc postfix variant which won't incorrectly call vmtruncate.
+ * The filesystem needs to handle block truncation upon failure.
  */
-int block_write_begin(struct file *file, struct address_space *mapping,
+int block_write_begin_newtrunc(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned flags,
                         struct page **pagep, void **fsdata,
                         get_block_t *get_block)
@@ -1992,20 +1989,50 @@ int block_write_begin(struct file *file, struct address_space *mapping,
                         unlock_page(page);
                         page_cache_release(page);
                         *pagep = NULL;
-
-                        /*
-                         * prepare_write() may have instantiated a few blocks
-                         * outside i_size.  Trim these off again. Don't need
-                         * i_size_read because we hold i_mutex.
-                         */
-                        if (pos + len > inode->i_size)
-                                vmtruncate(inode, inode->i_size);
                 }
         }
 
 out:
         return status;
 }
+EXPORT_SYMBOL(block_write_begin_newtrunc);
+
+/*
+ * block_write_begin takes care of the basic task of block allocation and
+ * bringing partial write blocks uptodate first.
+ *
+ * If *pagep is not NULL, then block_write_begin uses the locked page
+ * at *pagep rather than allocating its own. In this case, the page will
+ * not be unlocked or deallocated on failure.
+ */
+int block_write_begin(struct file *file, struct address_space *mapping,
+                        loff_t pos, unsigned len, unsigned flags,
+                        struct page **pagep, void **fsdata,
+                        get_block_t *get_block)
+{
+        int ret;
+
+        ret = block_write_begin_newtrunc(file, mapping, pos, len, flags,
+                                        pagep, fsdata, get_block);
+
+        /*
+         * prepare_write() may have instantiated a few blocks
+         * outside i_size.  Trim these off again. Don't need
+         * i_size_read because we hold i_mutex.
+         *
+         * Filesystems which pass down their own page also cannot
+         * call into vmtruncate here because it would lead to lock
+         * inversion problems (*pagep is locked). This is a further
+         * example of where the old truncate sequence is inadequate.
+         */
+        if (unlikely(ret) && *pagep == NULL) {
+                loff_t isize = mapping->host->i_size;
+                if (pos + len > isize)
+                        vmtruncate(mapping->host, isize);
+        }
+
+        return ret;
+}
 EXPORT_SYMBOL(block_write_begin);
 
 int block_write_end(struct file *file, struct address_space *mapping,
@@ -2324,7 +2351,7 @@ out:
  * For moronic filesystems that do not allow holes in file.
  * We may have to extend the file.
  */
-int cont_write_begin(struct file *file, struct address_space *mapping,
+int cont_write_begin_newtrunc(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned flags,
                         struct page **pagep, void **fsdata,
                         get_block_t *get_block, loff_t *bytes)
@@ -2345,11 +2372,30 @@ int cont_write_begin(struct file *file, struct address_space *mapping,
         }
 
         *pagep = NULL;
-        err = block_write_begin(file, mapping, pos, len,
+        err = block_write_begin_newtrunc(file, mapping, pos, len,
                                 flags, pagep, fsdata, get_block);
 out:
         return err;
 }
+EXPORT_SYMBOL(cont_write_begin_newtrunc);
+
+int cont_write_begin(struct file *file, struct address_space *mapping,
+                        loff_t pos, unsigned len, unsigned flags,
+                        struct page **pagep, void **fsdata,
+                        get_block_t *get_block, loff_t *bytes)
+{
+        int ret;
+
+        ret = cont_write_begin_newtrunc(file, mapping, pos, len, flags,
+                                        pagep, fsdata, get_block, bytes);
+        if (unlikely(ret)) {
+                loff_t isize = mapping->host->i_size;
+                if (pos + len > isize)
+                        vmtruncate(mapping->host, isize);
+        }
+
+        return ret;
+}
 EXPORT_SYMBOL(cont_write_begin);
 
 int block_prepare_write(struct page *page, unsigned from, unsigned to,
@@ -2381,7 +2427,7 @@ EXPORT_SYMBOL(block_commit_write);
  *
  * We are not allowed to take the i_mutex here so we have to play games to
  * protect against truncate races as the page could now be beyond EOF.  Because
- * vmtruncate() writes the inode size before removing pages, once we have the
+ * truncate writes the inode size before removing pages, once we have the
  * page lock we can determine safely if the page is beyond EOF. If it is not
  * beyond EOF, then the page is guaranteed safe against truncation until we
  * unlock the page.
@@ -2464,10 +2510,11 @@ static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
 }
 
 /*
- * On entry, the page is fully not uptodate.
- * On exit the page is fully uptodate in the areas outside (from,to)
+ * Filesystems implementing the new truncate sequence should use the
+ * _newtrunc postfix variant which won't incorrectly call vmtruncate.
+ * The filesystem needs to handle block truncation upon failure.
  */
-int nobh_write_begin(struct file *file, struct address_space *mapping,
+int nobh_write_begin_newtrunc(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned flags,
                         struct page **pagep, void **fsdata,
                         get_block_t *get_block)
@@ -2500,8 +2547,8 @@ int nobh_write_begin(struct file *file, struct address_space *mapping,
                 unlock_page(page);
                 page_cache_release(page);
                 *pagep = NULL;
-                return block_write_begin(file, mapping, pos, len, flags, pagep,
-                                        fsdata, get_block);
+                return block_write_begin_newtrunc(file, mapping, pos, len,
+                                        flags, pagep, fsdata, get_block);
         }
 
         if (PageMappedToDisk(page))
@@ -2605,8 +2652,34 @@ out_release:
         page_cache_release(page);
         *pagep = NULL;
 
-        if (pos + len > inode->i_size)
-                vmtruncate(inode, inode->i_size);
+        return ret;
+}
+EXPORT_SYMBOL(nobh_write_begin_newtrunc);
+
+/*
+ * On entry, the page is fully not uptodate.
+ * On exit the page is fully uptodate in the areas outside (from,to)
+ */
+int nobh_write_begin(struct file *file, struct address_space *mapping,
+                        loff_t pos, unsigned len, unsigned flags,
+                        struct page **pagep, void **fsdata,
+                        get_block_t *get_block)
+{
+        int ret;
+
+        ret = nobh_write_begin_newtrunc(file, mapping, pos, len, flags,
+                                        pagep, fsdata, get_block);
+
+        /*
+         * prepare_write() may have instantiated a few blocks
+         * outside i_size.  Trim these off again. Don't need
+         * i_size_read because we hold i_mutex.
+         */
+        if (unlikely(ret)) {
+                loff_t isize = mapping->host->i_size;
+                if (pos + len > isize)
+                        vmtruncate(mapping->host, isize);
+        }
 
         return ret;
 }
diff --git a/fs/direct-io.c b/fs/direct-io.c
index da111aacb46e..7600aacf531d 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1134,27 +1134,8 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
         return ret;
 }
 
-/*
- * This is a library function for use by filesystem drivers.
- *
- * The locking rules are governed by the flags parameter:
- *  - if the flags value contains DIO_LOCKING we use a fancy locking
- *    scheme for dumb filesystems.
- *    For writes this function is called under i_mutex and returns with
- *    i_mutex held, for reads, i_mutex is not held on entry, but it is
- *    taken and dropped again before returning.
- *    For reads and writes i_alloc_sem is taken in shared mode and released
- *    on I/O completion (which may happen asynchronously after returning to
- *    the caller).
- *
- *  - if the flags value does NOT contain DIO_LOCKING we don't use any
- *    internal locking but rather rely on the filesystem to synchronize
- *    direct I/O reads/writes versus each other and truncate.
- *    For reads and writes both i_mutex and i_alloc_sem are not held on
- *    entry and are never taken.
- */
 ssize_t
-__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+__blockdev_direct_IO_newtrunc(int rw, struct kiocb *iocb, struct inode *inode,
         struct block_device *bdev, const struct iovec *iov, loff_t offset, 
         unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
         dio_submit_t submit_io, int flags)
@@ -1247,9 +1228,46 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
                                 nr_segs, blkbits, get_block, end_io,
                                 submit_io, dio);
 
+out:
+        return retval;
+}
+EXPORT_SYMBOL(__blockdev_direct_IO_newtrunc);
+
+/*
+ * This is a library function for use by filesystem drivers.
+ *
+ * The locking rules are governed by the flags parameter:
+ *  - if the flags value contains DIO_LOCKING we use a fancy locking
+ *    scheme for dumb filesystems.
+ *    For writes this function is called under i_mutex and returns with
+ *    i_mutex held, for reads, i_mutex is not held on entry, but it is
+ *    taken and dropped again before returning.
+ *    For reads and writes i_alloc_sem is taken in shared mode and released
+ *    on I/O completion (which may happen asynchronously after returning to
+ *    the caller).
+ *
+ *  - if the flags value does NOT contain DIO_LOCKING we don't use any
+ *    internal locking but rather rely on the filesystem to synchronize
+ *    direct I/O reads/writes versus each other and truncate.
+ *    For reads and writes both i_mutex and i_alloc_sem are not held on
+ *    entry and are never taken.
+ */
+ssize_t
+__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+        struct block_device *bdev, const struct iovec *iov, loff_t offset,
+        unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
+        dio_submit_t submit_io, int flags)
+{
+        ssize_t retval;
+
+        retval = __blockdev_direct_IO_newtrunc(rw, iocb, inode, bdev, iov,
+                        offset, nr_segs, get_block, end_io, submit_io, flags);
         /*
          * In case of error extending write may have instantiated a few
          * blocks outside i_size. Trim these off again for DIO_LOCKING.
+         * NOTE: DIO_NO_LOCK/DIO_OWN_LOCK callers have to handle this in
+         * their own manner. This is a further example of where the old
+         * truncate sequence is inadequate.
          *
          * NOTE: filesystems with their own locking have to handle this
          * on their own.
@@ -1257,12 +1275,13 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
         if (flags & DIO_LOCKING) {
                 if (unlikely((rw & WRITE) && retval < 0)) {
                         loff_t isize = i_size_read(inode);
+                        loff_t end = offset + iov_length(iov, nr_segs);
+
                         if (end > isize)
                                 vmtruncate(inode, isize);
                 }
         }
 
-out:
         return retval;
 }
 EXPORT_SYMBOL(__blockdev_direct_IO);
diff --git a/fs/libfs.c b/fs/libfs.c
index b84d0a7a2204..09e1016eb774 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -8,6 +8,7 @@
 #include <linux/slab.h>
 #include <linux/mount.h>
 #include <linux/vfs.h>
+#include <linux/quotaops.h>
 #include <linux/mutex.h>
 #include <linux/exportfs.h>
 #include <linux/writeback.h>
@@ -325,6 +326,81 @@ int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
         return 0;
 }
 
+/**
+ * simple_setsize - handle core mm and vfs requirements for file size change
+ * @inode: inode
+ * @newsize: new file size
+ *
+ * Returns 0 on success, -error on failure.
+ *
+ * simple_setsize must be called with inode_mutex held.
+ *
+ * simple_setsize will check that the requested new size is OK (see
+ * inode_newsize_ok), and then will perform the necessary i_size update
+ * and pagecache truncation (if necessary). It will be typically be called
+ * from the filesystem's setattr function when ATTR_SIZE is passed in.
+ *
+ * The inode itself must have correct permissions and attributes to allow
+ * i_size to be changed, this function then just checks that the new size
+ * requested is valid.
+ *
+ * In the case of simple in-memory filesystems with inodes stored solely
+ * in the inode cache, and file data in the pagecache, nothing more needs
+ * to be done to satisfy a truncate request. Filesystems with on-disk
+ * blocks for example will need to free them in the case of truncate, in
+ * that case it may be easier not to use simple_setsize (but each of its
+ * components will likely be required at some point to update pagecache
+ * and inode etc).
+ */
+int simple_setsize(struct inode *inode, loff_t newsize)
+{
+        loff_t oldsize;
+        int error;
+
+        error = inode_newsize_ok(inode, newsize);
+        if (error)
+                return error;
+
+        oldsize = inode->i_size;
+        i_size_write(inode, newsize);
+        truncate_pagecache(inode, oldsize, newsize);
+
+        return error;
+}
+EXPORT_SYMBOL(simple_setsize);
+
+/**
+ * simple_setattr - setattr for simple in-memory filesystem
+ * @dentry: dentry
+ * @iattr: iattr structure
+ *
+ * Returns 0 on success, -error on failure.
+ *
+ * simple_setattr implements setattr for an in-memory filesystem which
+ * does not store its own file data or metadata (eg. uses the page cache
+ * and inode cache as its data store).
+ */
+int simple_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        error = inode_change_ok(inode, iattr);
+        if (error)
+                return error;
+
+        if (iattr->ia_valid & ATTR_SIZE) {
+                error = simple_setsize(inode, iattr->ia_size);
+                if (error)
+                        return error;
+        }
+
+        generic_setattr(inode, iattr);
+
+        return error;
+}
+EXPORT_SYMBOL(simple_setattr);
+
 int simple_readpage(struct file *file, struct page *page)
 {
         clear_highpage(page);