[PATCH] VFS: pass file pointer to filesystem from ftruncate()

This patch extends the iattr structure with a file pointer memeber, and adds
an ATTR_FILE validity flag for this member.

This is set if do_truncate() is invoked from ftruncate() or from
do_coredump().

The change is source and binary compatible.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 18 insertions, 6 deletions

diff --git a/fs/exec.c b/fs/exec.c
index ce76b33f25ac..cd6c574557dc 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1511,7 +1511,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
                 goto close_fail;
         if (!file->f_op->write)
                 goto close_fail;
-        if (do_truncate(file->f_dentry, 0) != 0)
+        if (do_truncate(file->f_dentry, 0, file) != 0)
                 goto close_fail;
 
         retval = binfmt->core_dump(signr, regs, file);
diff --git a/fs/namei.c b/fs/namei.c
index c5769c4fcab1..b3f8a1966c9c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1459,7 +1459,7 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
                 if (!error) {
                         DQUOT_INIT(inode);
                         
-                        error = do_truncate(dentry, 0);
+                        error = do_truncate(dentry, 0, NULL);
                 }
                 put_write_access(inode);
                 if (error)
diff --git a/fs/open.c b/fs/open.c
index 2835f096c683..6e8136751e9a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -194,7 +194,7 @@ out:
         return error;
 }
 
-int do_truncate(struct dentry *dentry, loff_t length)
+int do_truncate(struct dentry *dentry, loff_t length, struct file *filp)
 {
         int err;
         struct iattr newattrs;
@@ -205,6 +205,10 @@ int do_truncate(struct dentry *dentry, loff_t length)
 
         newattrs.ia_size = length;
         newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
+        if (filp) {
+                newattrs.ia_file = filp;
+                newattrs.ia_valid |= ATTR_FILE;
+        }
 
         down(&dentry->d_inode->i_sem);
         err = notify_change(dentry, &newattrs);
@@ -262,7 +266,7 @@ static inline long do_sys_truncate(const char __user * path, loff_t length)
         error = locks_verify_truncate(inode, NULL, length);
         if (!error) {
                 DQUOT_INIT(inode);
-                error = do_truncate(nd.dentry, length);
+                error = do_truncate(nd.dentry, length, NULL);
         }
         put_write_access(inode);
 
@@ -314,7 +318,7 @@ static inline long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 
         error = locks_verify_truncate(inode, file, length);
         if (!error)
-                error = do_truncate(dentry, length);
+                error = do_truncate(dentry, length, file);
 out_putf:
         fput(file);
 out:
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6d6226732c93..0c89fc9481a8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -264,6 +264,7 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 #define ATTR_ATTR_FLAG  1024
 #define ATTR_KILL_SUID  2048
 #define ATTR_KILL_SGID  4096
+#define ATTR_FILE       8192
 
 /*
  * This is the Inode Attributes structure, used for notify_change().  It
@@ -283,6 +284,13 @@ struct iattr {
         struct timespec ia_atime;
         struct timespec ia_mtime;
         struct timespec ia_ctime;
+
+        /*
+         * Not an attribute, but an auxilary info for filesystems wanting to
+         * implement an ftruncate() like method.  NOTE: filesystem should
+         * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
+         */
+        struct file     *ia_file;
 };
 
 /*
@@ -1288,7 +1296,7 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
 
 /* fs/open.c */
 
-extern int do_truncate(struct dentry *, loff_t start);
+extern int do_truncate(struct dentry *, loff_t start, struct file *filp);
 extern long do_sys_open(const char __user *filename, int flags, int mode);
 extern struct file *filp_open(const char *, int, int);
 extern struct file * dentry_open(struct dentry *, struct vfsmount *, int);