Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull parallel filesystem directory handling update from Al Viro.

This is the main parallel directory work by Al that makes the vfs layer
able to do lookup and readdir in parallel within a single directory.
That's a big change, since this used to be all protected by the
directory inode mutex.

The inode mutex is replaced by an rwsem, and serialization of lookups of
a single name is done by a "in-progress" dentry marker.

The series begins with xattr cleanups, and then ends with switching
filesystems over to actually doing the readdir in parallel (switching to
the "iterate_shared()" that only takes the read lock).

A more detailed explanation of the process from Al Viro:
 "The xattr work starts with some acl fixes, then switches ->getxattr to
  passing inode and dentry separately.  This is the point where the
  things start to get tricky - that got merged into the very beginning
  of the -rc3-based #work.lookups, to allow untangling the
  security_d_instantiate() mess.  The xattr work itself proceeds to
  switch a lot of filesystems to generic_...xattr(); no complications
  there.

  After that initial xattr work, the series then does the following:

   - untangle security_d_instantiate()

   - convert a bunch of open-coded lookup_one_len_unlocked() to calls of
     that thing; one such place (in overlayfs) actually yields a trivial
     conflict with overlayfs fixes later in the cycle - overlayfs ended
     up switching to a variant of lookup_one_len_unlocked() sans the
     permission checks.  I would've dropped that commit (it gets
     overridden on merge from #ovl-fixes in #for-next; proper resolution
     is to use the variant in mainline fs/overlayfs/super.c), but I
     didn't want to rebase the damn thing - it was fairly late in the
     cycle...

   - some filesystems had managed to depend on lookup/lookup exclusion
     for *fs-internal* data structures in a way that would break if we
     relaxed the VFS exclusion.  Fixing hadn't been hard, fortunately.

   - core of that series - parallel lookup machinery, replacing
     ->i_mutex with rwsem, making lookup_slow() take it only shared.  At
     that point lookups happen in parallel; lookups on the same name
     wait for the in-progress one to be done with that dentry.

     Surprisingly little code, at that - almost all of it is in
     fs/dcache.c, with fs/namei.c changes limited to lookup_slow() -
     making it use the new primitive and actually switching to locking
     shared.

   - parallel readdir stuff - first of all, we provide the exclusion on
     per-struct file basis, same as we do for read() vs lseek() for
     regular files.  That takes care of most of the needed exclusion in
     readdir/readdir; however, these guys are trickier than lookups, so
     I went for switching them one-by-one.  To do that, a new method
     '->iterate_shared()' is added and filesystems are switched to it
     as they are either confirmed to be OK with shared lock on directory
     or fixed to be OK with that.  I hope to kill the original method
     come next cycle (almost all in-tree filesystems are switched
     already), but it's still not quite finished.

   - several filesystems get switched to parallel readdir.  The
     interesting part here is dealing with dcache preseeding by readdir;
     that needs minor adjustment to be safe with directory locked only
     shared.

     Most of the filesystems doing that got switched to in those
     commits.  Important exception: NFS.  Turns out that NFS folks, with
     their, er, insistence on VFS getting the fuck out of the way of the
     Smart Filesystem Code That Knows How And What To Lock(tm) have
     grown the locking of their own.  They had their own homegrown
     rwsem, with lookup/readdir/atomic_open being *writers* (sillyunlink
     is the reader there).  Of course, with VFS getting the fuck out of
     the way, as requested, the actual smarts of the smart filesystem
     code etc. had become exposed...

   - do_last/lookup_open/atomic_open cleanups.  As the result, open()
     without O_CREAT locks the directory only shared.  Including the
     ->atomic_open() case.  Backmerge from #for-linus in the middle of
     that - atomic_open() fix got brought in.

   - then comes NFS switch to saner (VFS-based ;-) locking, killing the
     homegrown "lookup and readdir are writers" kinda-sorta rwsem.  All
     exclusion for sillyunlink/lookup is done by the parallel lookups
     mechanism.  Exclusion between sillyunlink and rmdir is a real rwsem
     now - rmdir being the writer.

     Result: NFS lookups/readdirs/O_CREAT-less opens happen in parallel
     now.

   - the rest of the series consists of switching a lot of filesystems
     to parallel readdir; in a lot of cases ->llseek() gets simplified
     as well.  One backmerge in there (again, #for-linus - rockridge
     fix)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (74 commits)
  ext4: switch to ->iterate_shared()
  hfs: switch to ->iterate_shared()
  hfsplus: switch to ->iterate_shared()
  hostfs: switch to ->iterate_shared()
  hpfs: switch to ->iterate_shared()
  hpfs: handle allocation failures in hpfs_add_pos()
  gfs2: switch to ->iterate_shared()
  f2fs: switch to ->iterate_shared()
  afs: switch to ->iterate_shared()
  befs: switch to ->iterate_shared()
  befs: constify stuff a bit
  isofs: switch to ->iterate_shared()
  get_acorn_filename(): deobfuscate a bit
  btrfs: switch to ->iterate_shared()
  logfs: no need to lock directory in lseek
  switch ecryptfs to ->iterate_shared
  9p: switch to ->iterate_shared()
  fat: switch to ->iterate_shared()
  romfs, squashfs: switch to ->iterate_shared()
  more trivial ->iterate_shared conversions
  ...

7 files changed, 39 insertions, 32 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 0d163a8..ff4527d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1820,12 +1820,17 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx,
 
 	child = d_hash_and_lookup(dir, &qname);
 	if (!child) {
-		child = d_alloc(dir, &qname);
-		if (!child)
-			goto end_instantiate;
-		if (instantiate(d_inode(dir), child, task, ptr) < 0) {
-			dput(child);
+		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		child = d_alloc_parallel(dir, &qname, &wq);
+		if (IS_ERR(child))
 			goto end_instantiate;
+		if (d_in_lookup(child)) {
+			int err = instantiate(d_inode(dir), child, task, ptr);
+			d_lookup_done(child);
+			if (err < 0) {
+				dput(child);
+				goto end_instantiate;
+			}
 		}
 	}
 	inode = d_inode(child);
@@ -2155,8 +2160,8 @@ out:
 
 static const struct file_operations proc_map_files_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_map_files_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_map_files_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
@@ -2503,8 +2508,8 @@ static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
 
 static const struct file_operations proc_attr_dir_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_attr_dir_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_attr_dir_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 static struct dentry *proc_attr_dir_lookup(struct inode *dir,
@@ -2911,8 +2916,8 @@ static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
 
 static const struct file_operations proc_tgid_base_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_tgid_base_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_tgid_base_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
@@ -3259,8 +3264,8 @@ static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *den
 
 static const struct file_operations proc_tid_base_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_tid_base_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_tid_base_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 static const struct inode_operations proc_tid_base_inode_operations = {
@@ -3470,6 +3475,6 @@ static const struct inode_operations proc_task_inode_operations = {
 
 static const struct file_operations proc_task_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_task_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_task_readdir,
+	.llseek		= generic_file_llseek,
 };
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 56afa5e..01df23c 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -276,8 +276,8 @@ static int proc_readfd(struct file *file, struct dir_context *ctx)
 
 const struct file_operations proc_fd_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_readfd,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_readfd,
+	.llseek		= generic_file_llseek,
 };
 
 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
@@ -361,6 +361,6 @@ const struct inode_operations proc_fdinfo_inode_operations = {
 
 const struct file_operations proc_fdinfo_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_readfdinfo,
-	.llseek		= default_llseek,
+	.iterate_shared	= proc_readfdinfo,
+	.llseek		= generic_file_llseek,
 };
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index ff3ffc7..c633476 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -318,7 +318,7 @@ int proc_readdir(struct file *file, struct dir_context *ctx)
 static const struct file_operations proc_dir_operations = {
 	.llseek			= generic_file_llseek,
 	.read			= generic_read_dir,
-	.iterate		= proc_readdir,
+	.iterate_shared		= proc_readdir,
 };
 
 /*
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 72cb26f..51b8b0a 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -139,7 +139,8 @@ out:
 
 const struct file_operations proc_ns_dir_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_ns_dir_readdir,
+	.iterate_shared	= proc_ns_dir_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 static struct dentry *proc_ns_dir_lookup(struct inode *dir,
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 350984a..c8bbc68 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -179,7 +179,7 @@ static int proc_tgid_net_readdir(struct file *file, struct dir_context *ctx)
 const struct file_operations proc_net_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
-	.iterate	= proc_tgid_net_readdir,
+	.iterate_shared	= proc_tgid_net_readdir,
 };
 
 static __net_init int proc_net_ns_init(struct net *net)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index fe5b6e6..5e57c3e 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -627,18 +627,19 @@ static bool proc_sys_fill_cache(struct file *file,
 
 	child = d_lookup(dir, &qname);
 	if (!child) {
-		child = d_alloc(dir, &qname);
-		if (child) {
+		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		child = d_alloc_parallel(dir, &qname, &wq);
+		if (IS_ERR(child))
+			return false;
+		if (d_in_lookup(child)) {
 			inode = proc_sys_make_inode(dir->d_sb, head, table);
 			if (!inode) {
+				d_lookup_done(child);
 				dput(child);
 				return false;
-			} else {
-				d_set_d_op(child, &proc_sys_dentry_operations);
-				d_add(child, inode);
 			}
-		} else {
-			return false;
+			d_set_d_op(child, &proc_sys_dentry_operations);
+			d_add(child, inode);
 		}
 	}
 	inode = d_inode(child);
@@ -789,7 +790,7 @@ static const struct file_operations proc_sys_file_operations = {
 
 static const struct file_operations proc_sys_dir_file_operations = {
 	.read		= generic_read_dir,
-	.iterate	= proc_sys_readdir,
+	.iterate_shared	= proc_sys_readdir,
 	.llseek		= generic_file_llseek,
 };
 
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 361ab4e..55bc7d6 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -226,8 +226,8 @@ static int proc_root_readdir(struct file *file, struct dir_context *ctx)
  */
 static const struct file_operations proc_root_operations = {
 	.read		 = generic_read_dir,
-	.iterate	 = proc_root_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	 = proc_root_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 /*