Remove BKL from remote_llseek v2

- Replace remote_llseek with generic_file_llseek_unlocked (to force compilation
failures in all users)
- Change all users to either use generic_file_llseek_unlocked directly or
take the BKL around. I changed the file systems who don't use the BKL
for anything (CIFS, GFS) to call it directly. NCPFS and SMBFS and NFS
take the BKL, but explicitely in their own source now.

I moved them all over in a single patch to avoid unbisectable sections.

Open problem: 32bit kernels can corrupt fpos because its modification
is not atomic, but they can do that anyways because there's other paths who
modify it without BKL.

Do we need a special lock for the pos/f_version = 0 checks?

Trond says the NFS BKL is likely not needed, but keep it for now
until his full audit.

v2: Use generic_file_llseek_unlocked instead of remote_llseek_unlocked
    and factor duplicated code (suggested by hch)

Cc: Trond.Myklebust@netapp.com
Cc: swhiteho@redhat.com
Cc: sfrench@samba.org
Cc: vandrove@vc.cvut.cz

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

1 files changed, 11 insertions, 27 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index f0d1240a5c69..9ba495d5a29b 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -31,12 +31,12 @@ const struct file_operations generic_ro_fops = {
 
 EXPORT_SYMBOL(generic_ro_fops);
 
-loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
+loff_t
+generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
 {
         loff_t retval;
         struct inode *inode = file->f_mapping->host;
 
-        mutex_lock(&inode->i_mutex);
         switch (origin) {
                 case SEEK_END:
                         offset += inode->i_size;
@@ -46,42 +46,26 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
         }
         retval = -EINVAL;
         if (offset>=0 && offset<=inode->i_sb->s_maxbytes) {
+                /* Special lock needed here? */
                 if (offset != file->f_pos) {
                         file->f_pos = offset;
                         file->f_version = 0;
                 }
                 retval = offset;
         }
-        mutex_unlock(&inode->i_mutex);
         return retval;
 }
+EXPORT_SYMBOL(generic_file_llseek_unlocked);
 
-EXPORT_SYMBOL(generic_file_llseek);
-
-loff_t remote_llseek(struct file *file, loff_t offset, int origin)
+loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
 {
-        loff_t retval;
-
-        lock_kernel();
-        switch (origin) {
-                case SEEK_END:
-                        offset += i_size_read(file->f_path.dentry->d_inode);
-                        break;
-                case SEEK_CUR:
-                        offset += file->f_pos;
-        }
-        retval = -EINVAL;
-        if (offset>=0 && offset<=file->f_path.dentry->d_inode->i_sb->s_maxbytes) {
-                if (offset != file->f_pos) {
-                        file->f_pos = offset;
-                        file->f_version = 0;
-                }
-                retval = offset;
-        }
-        unlock_kernel();
-        return retval;
+        loff_t n;
+        mutex_lock(&file->f_dentry->d_inode->i_mutex);
+        n = generic_file_llseek_unlocked(file, offset, origin);
+        mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+        return n;
 }
-EXPORT_SYMBOL(remote_llseek);
+EXPORT_SYMBOL(generic_file_llseek);
 
 loff_t no_llseek(struct file *file, loff_t offset, int origin)
 {