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mark struct file that had write access grabbed by open()

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new flag in ->f_mode - FMODE_WRITER.  Set by do_dentry_open() in case
when it has grabbed write access, checked by __fput() to decide whether
it wants to drop the sucker.  Allows to stop bothering with mnt_clone_write()
in alloc_file(), along with fewer special_file() checks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2014-03-14 12:02:47 -04:00
parent 0ccb286346
commit 83f936c75e
4 changed files with 11 additions and 41 deletions
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37
fs/file_table.c
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@@ -177,43 +177,12 @@ struct file *alloc_file(struct path *path, fmode_t mode,
file->f_mapping = path->dentry->d_inode->i_mapping;
file->f_mode = mode;
file->f_op = fop;
/*
* These mounts don't really matter in practice
* for r/o bind mounts. They aren't userspace-
* visible. We do this for consistency, and so
* that we can do debugging checks at __fput()
*/
if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
WARN_ON(mnt_clone_write(path->mnt));
}
if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
i_readcount_inc(path->dentry->d_inode);
return file;
}
EXPORT_SYMBOL(alloc_file);
/**
* drop_file_write_access - give up ability to write to a file
* @file: the file to which we will stop writing
*
* This is a central place which will give up the ability
* to write to @file, along with access to write through
* its vfsmount.
*/
static void drop_file_write_access(struct file *file)
{
struct vfsmount *mnt = file->f_path.mnt;
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
if (special_file(inode->i_mode))
return;
put_write_access(inode);
__mnt_drop_write(mnt);
}
/* the real guts of fput() - releasing the last reference to file
*/
static void __fput(struct file *file)
@@ -248,8 +217,10 @@ static void __fput(struct file *file)
put_pid(file->f_owner.pid);
if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
i_readcount_dec(inode);
if (file->f_mode & FMODE_WRITE)
drop_file_write_access(file);
if (file->f_mode & FMODE_WRITER) {
put_write_access(inode);
__mnt_drop_write(mnt);
}
file->f_path.dentry = NULL;
file->f_path.mnt = NULL;
file->f_inode = NULL;