Merge branch 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block

* 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block:
  [PATCH] Remove SUID when splicing into an inode
  [PATCH] Add lockless helpers for remove_suid()
  [PATCH] Introduce generic_file_splice_write_nolock()
  [PATCH] Take i_mutex in splice_from_pipe()

4 files changed, 148 insertions, 30 deletions

diff --git a/fs/inode.c b/fs/inode.c
index d9a21d122926..26cdb115ce67 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1306,6 +1306,42 @@ void wake_up_inode(struct inode *inode)
         wake_up_bit(&inode->i_state, __I_LOCK);
 }
 
+/*
+ * We rarely want to lock two inodes that do not have a parent/child
+ * relationship (such as directory, child inode) simultaneously. The
+ * vast majority of file systems should be able to get along fine
+ * without this. Do not use these functions except as a last resort.
+ */
+void inode_double_lock(struct inode *inode1, struct inode *inode2)
+{
+        if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
+                if (inode1)
+                        mutex_lock(&inode1->i_mutex);
+                else if (inode2)
+                        mutex_lock(&inode2->i_mutex);
+                return;
+        }
+
+        if (inode1 < inode2) {
+                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
+        } else {
+                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
+        }
+}
+EXPORT_SYMBOL(inode_double_lock);
+
+void inode_double_unlock(struct inode *inode1, struct inode *inode2)
+{
+        if (inode1)
+                mutex_unlock(&inode1->i_mutex);
+
+        if (inode2 && inode2 != inode1)
+                mutex_unlock(&inode2->i_mutex);
+}
+EXPORT_SYMBOL(inode_double_unlock);
+
 static __initdata unsigned long ihash_entries;
 static int __init set_ihash_entries(char *str)
 {
diff --git a/fs/splice.c b/fs/splice.c
index a567010b62ac..49fb9f129938 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -707,9 +707,9 @@ out_ret:
  * key here is the 'actor' worker passed in that actually moves the data
  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
  */
-ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
-                         loff_t *ppos, size_t len, unsigned int flags,
-                         splice_actor *actor)
+static ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
+                                  struct file *out, loff_t *ppos, size_t len,
+                                  unsigned int flags, splice_actor *actor)
 {
         int ret, do_wakeup, err;
         struct splice_desc sd;
@@ -722,9 +722,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
         sd.file = out;
         sd.pos = *ppos;
 
-        if (pipe->inode)
-                mutex_lock(&pipe->inode->i_mutex);
-
         for (;;) {
                 if (pipe->nrbufs) {
                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
@@ -797,9 +794,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                 pipe_wait(pipe);
         }
 
-        if (pipe->inode)
-                mutex_unlock(&pipe->inode->i_mutex);
-
         if (do_wakeup) {
                 smp_mb();
                 if (waitqueue_active(&pipe->wait))
@@ -810,6 +804,73 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
         return ret;
 }
 
+ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
+                         loff_t *ppos, size_t len, unsigned int flags,
+                         splice_actor *actor)
+{
+        ssize_t ret;
+        struct inode *inode = out->f_mapping->host;
+
+        /*
+         * The actor worker might be calling ->prepare_write and
+         * ->commit_write. Most of the time, these expect i_mutex to
+         * be held. Since this may result in an ABBA deadlock with
+         * pipe->inode, we have to order lock acquiry here.
+         */
+        inode_double_lock(inode, pipe->inode);
+        ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
+        inode_double_unlock(inode, pipe->inode);
+
+        return ret;
+}
+
+/**
+ * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
+ * @pipe:       pipe info
+ * @out:        file to write to
+ * @len:        number of bytes to splice
+ * @flags:      splice modifier flags
+ *
+ * Will either move or copy pages (determined by @flags options) from
+ * the given pipe inode to the given file. The caller is responsible
+ * for acquiring i_mutex on both inodes.
+ *
+ */
+ssize_t
+generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
+                                 loff_t *ppos, size_t len, unsigned int flags)
+{
+        struct address_space *mapping = out->f_mapping;
+        struct inode *inode = mapping->host;
+        ssize_t ret;
+        int err;
+
+        err = remove_suid(out->f_dentry);
+        if (unlikely(err))
+                return err;
+
+        ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
+        if (ret > 0) {
+                *ppos += ret;
+
+                /*
+                 * If file or inode is SYNC and we actually wrote some data,
+                 * sync it.
+                 */
+                if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
+                        err = generic_osync_inode(inode, mapping,
+                                                  OSYNC_METADATA|OSYNC_DATA);
+
+                        if (err)
+                                ret = err;
+                }
+        }
+
+        return ret;
+}
+
+EXPORT_SYMBOL(generic_file_splice_write_nolock);
+
 /**
  * generic_file_splice_write - splice data from a pipe to a file
  * @pipe:       pipe info
@@ -826,12 +887,21 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
                           loff_t *ppos, size_t len, unsigned int flags)
 {
         struct address_space *mapping = out->f_mapping;
+        struct inode *inode = mapping->host;
         ssize_t ret;
+        int err;
+
+        err = should_remove_suid(out->f_dentry);
+        if (unlikely(err)) {
+                mutex_lock(&inode->i_mutex);
+                err = __remove_suid(out->f_dentry, err);
+                mutex_unlock(&inode->i_mutex);
+                if (err)
+                        return err;
+        }
 
         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
         if (ret > 0) {
-                struct inode *inode = mapping->host;
-
                 *ppos += ret;
 
                 /*
@@ -839,8 +909,6 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
                  * sync it.
                  */
                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
-                        int err;
-
                         mutex_lock(&inode->i_mutex);
                         err = generic_osync_inode(inode, mapping,
                                                   OSYNC_METADATA|OSYNC_DATA);
@@ -1400,13 +1468,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
          * grabbing by inode address. Otherwise two different processes
          * could deadlock (one doing tee from A -> B, the other from B -> A).
          */
-        if (ipipe->inode < opipe->inode) {
-                mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_PARENT);
-                mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_CHILD);
-        } else {
-                mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_PARENT);
-                mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_CHILD);
-        }
+        inode_double_lock(ipipe->inode, opipe->inode);
 
         do {
                 if (!opipe->readers) {
@@ -1450,8 +1512,7 @@ static int link_pipe(struct pipe_inode_info *ipipe,
                 i++;
         } while (len);
 
-        mutex_unlock(&ipipe->inode->i_mutex);
-        mutex_unlock(&opipe->inode->i_mutex);
+        inode_double_unlock(ipipe->inode, opipe->inode);
 
         /*
          * If we put data in the output pipe, wakeup any potential readers.
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 661c7c572149..2fe6e3f900ba 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -623,6 +623,9 @@ enum inode_i_mutex_lock_class
         I_MUTEX_QUOTA
 };
 
+extern void inode_double_lock(struct inode *inode1, struct inode *inode2);
+extern void inode_double_unlock(struct inode *inode1, struct inode *inode2);
+
 /*
  * NOTE: in a 32bit arch with a preemptable kernel and
  * an UP compile the i_size_read/write must be atomic
@@ -1709,6 +1712,8 @@ extern void __iget(struct inode * inode);
 extern void clear_inode(struct inode *);
 extern void destroy_inode(struct inode *);
 extern struct inode *new_inode(struct super_block *);
+extern int __remove_suid(struct dentry *, int);
+extern int should_remove_suid(struct dentry *);
 extern int remove_suid(struct dentry *);
 extern void remove_dquot_ref(struct super_block *, int, struct list_head *);
 
@@ -1755,6 +1760,8 @@ extern ssize_t generic_file_splice_read(struct file *, loff_t *,
                 struct pipe_inode_info *, size_t, unsigned int);
 extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
                 struct file *, loff_t *, size_t, unsigned int);
+extern ssize_t generic_file_splice_write_nolock(struct pipe_inode_info *,
+                struct file *, loff_t *, size_t, unsigned int);
 extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
                 struct file *out, loff_t *, size_t len, unsigned int flags);
 extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
diff --git a/mm/filemap.c b/mm/filemap.c
index 8558732e85c1..cb26e33fd0ff 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1884,11 +1884,10 @@ repeat:
  *      if suid or (sgid and xgrp)
  *              remove privs
  */
-int remove_suid(struct dentry *dentry)
+int should_remove_suid(struct dentry *dentry)
 {
         mode_t mode = dentry->d_inode->i_mode;
         int kill = 0;
-        int result = 0;
 
         /* suid always must be killed */
         if (unlikely(mode & S_ISUID))
@@ -1901,13 +1900,28 @@ int remove_suid(struct dentry *dentry)
         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
                 kill |= ATTR_KILL_SGID;
 
-        if (unlikely(kill && !capable(CAP_FSETID))) {
-                struct iattr newattrs;
+        if (unlikely(kill && !capable(CAP_FSETID)))
+                return kill;
 
-                newattrs.ia_valid = ATTR_FORCE | kill;
-                result = notify_change(dentry, &newattrs);
-        }
-        return result;
+        return 0;
+}
+
+int __remove_suid(struct dentry *dentry, int kill)
+{
+        struct iattr newattrs;
+
+        newattrs.ia_valid = ATTR_FORCE | kill;
+        return notify_change(dentry, &newattrs);
+}
+
+int remove_suid(struct dentry *dentry)
+{
+        int kill = should_remove_suid(dentry);
+
+        if (unlikely(kill))
+                return __remove_suid(dentry, kill);
+
+        return 0;
 }
 EXPORT_SYMBOL(remove_suid);