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From: ebiederm@xmission.com (Eric W. Biederman)
To: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>,
	<linux-mm@kvack.org>, <linux-fsdevel@vger.kernel.org>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Hugh Dickins <hugh@veritas.com>, Tejun Heo <tj@kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@suse.de>
Subject: [RFC][PATCH 4/9] vfs: Generalize the file_list
Date: Sat, 11 Apr 2009 05:07:39 -0700
Message-ID: <m1ab6n75ro.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <m1skkf761y.fsf@fess.ebiederm.org> (Eric W. Biederman's message of "Sat\, 11 Apr 2009 05\:01\:29 -0700")


file_list_lock is held when files are being revoked
aka hung up on in tty_io, and also needs to be done
in a more general revoke case.  The more general revoke
case also needs to sleep so I have converted file_list_lock
into a mutex.

To make it clear what is on the file list and when I have changed
file_move to file_add.  The callers have been modified to to ensure
file_add is called exactly once on a file.  In __dentry_open
file_add is called on everything except device files.  In __ptmx_open
and __tty_open file_add is called to place the ttys on the tty_files
list.

To make using the file_list for efficient for handling revokes
I have moved the list head from the superblock to the inode.
This means only relevant files need to be looked at.

fs_may_remount_ro and mark_files_ro have been modified to
walk the inode list to find all of the inodes and then to
walk the file list on those inodes.  It is a slightly slower
process but just as efficient and potentially more correct
as inodes may have some influence on the the rw state of the
filesystem that files do not.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 drivers/char/pty.c    |    2 +-
 drivers/char/tty_io.c |    2 +-
 fs/file_table.c       |   27 ++++++++++++++++++---------
 fs/inode.c            |    1 +
 fs/open.c             |    3 ++-
 fs/super.c            |   49 +++++++++++++++++++++++++++----------------------
 include/linux/fs.h    |   10 +++++-----
 7 files changed, 55 insertions(+), 39 deletions(-)

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 31038a0..3ed304c 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -662,7 +662,7 @@ static int __ptmx_open(struct inode *inode, struct file *filp)
 
 	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 	filp->private_data = tty;
-	file_move(filp, &tty->tty_files);
+	file_add(filp, &tty->tty_files);
 
 	retval = devpts_pty_new(inode, tty->link);
 	if (retval)
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 66b99a2..22b978e 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1836,7 +1836,7 @@ got_driver:
 		return PTR_ERR(tty);
 
 	filp->private_data = tty;
-	file_move(filp, &tty->tty_files);
+	file_add(filp, &tty->tty_files);
 	check_tty_count(tty, "tty_open");
 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
 	    tty->driver->subtype == PTY_TYPE_MASTER)
diff --git a/fs/file_table.c b/fs/file_table.c
index 54018fe..03d74b6 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -22,6 +22,7 @@
 #include <linux/fsnotify.h>
 #include <linux/sysctl.h>
 #include <linux/percpu_counter.h>
+#include <linux/writeback.h>
 
 #include <asm/atomic.h>
 
@@ -31,7 +32,7 @@ struct files_stat_struct files_stat = {
 };
 
 /* public. Not pretty! */
-__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
+__cacheline_aligned_in_smp DEFINE_MUTEX(files_lock);
 
 /* SLAB cache for file structures */
 static struct kmem_cache *filp_cachep __read_mostly;
@@ -357,12 +358,12 @@ void put_filp(struct file *file)
 	}
 }
 
-void file_move(struct file *file, struct list_head *list)
+void file_add(struct file *file, struct list_head *list)
 {
 	if (!list)
 		return;
 	file_list_lock();
-	list_move(&file->f_u.fu_list, list);
+	list_add(&file->f_u.fu_list, list);
 	file_list_unlock();
 }
 
@@ -377,24 +378,32 @@ void file_kill(struct file *file)
 
 int fs_may_remount_ro(struct super_block *sb)
 {
+	struct inode *inode;
 	struct file *file;
 
 	/* Check that no files are currently opened for writing. */
 	file_list_lock();
-	list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
-		struct inode *inode = file->f_path.dentry->d_inode;
-
+	spin_lock(&inode_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
 		/* File with pending delete? */
 		if (inode->i_nlink == 0)
 			goto too_bad;
 
-		/* Writeable file? */
-		if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
-			goto too_bad;
+		/* Regular file */
+		if (!S_ISREG(inode->i_mode))
+			continue;
+
+		list_for_each_entry(file, &inode->i_files, f_u.fu_list) {
+			/* Writeable file? */
+			if (file->f_mode & FMODE_WRITE)
+				goto too_bad;
+		}
 	}
+	spin_unlock(&inode_lock);
 	file_list_unlock();
 	return 1; /* Tis' cool bro. */
 too_bad:
+	spin_unlock(&inode_lock);
 	file_list_unlock();
 	return 0;
 }
diff --git a/fs/inode.c b/fs/inode.c
index d06d6d2..9682caf 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -238,6 +238,7 @@ void inode_init_once(struct inode *inode)
 	memset(inode, 0, sizeof(*inode));
 	INIT_HLIST_NODE(&inode->i_hash);
 	INIT_LIST_HEAD(&inode->i_dentry);
+	INIT_LIST_HEAD(&inode->i_files);
 	INIT_LIST_HEAD(&inode->i_devices);
 	INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
 	spin_lock_init(&inode->i_data.tree_lock);
diff --git a/fs/open.c b/fs/open.c
index 377eb25..5e201cb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -828,7 +828,8 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 	f->f_path.mnt = mnt;
 	f->f_pos = 0;
 	f->f_op = fops_get(inode->i_fop);
-	file_move(f, &inode->i_sb->s_files);
+	if (!special_file(inode->i_mode))
+		file_add(f, &inode->i_files);
 
 	error = security_dentry_open(f, cred);
 	if (error)
diff --git a/fs/super.c b/fs/super.c
index 786fe7d..e55299c 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -67,7 +67,6 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		INIT_LIST_HEAD(&s->s_dirty);
 		INIT_LIST_HEAD(&s->s_io);
 		INIT_LIST_HEAD(&s->s_more_io);
-		INIT_LIST_HEAD(&s->s_files);
 		INIT_LIST_HEAD(&s->s_instances);
 		INIT_HLIST_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
@@ -597,32 +596,38 @@ out:
 
 static void mark_files_ro(struct super_block *sb)
 {
+	struct inode *inode;
 	struct file *f;
 
 retry:
 	file_list_lock();
-	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
-		struct vfsmount *mnt;
-		if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
-		       continue;
-		if (!file_count(f))
-			continue;
-		if (!(f->f_mode & FMODE_WRITE))
-			continue;
-		f->f_mode &= ~FMODE_WRITE;
-		if (file_check_writeable(f) != 0)
-			continue;
-		file_release_write(f);
-		mnt = mntget(f->f_path.mnt);
-		file_list_unlock();
-		/*
-		 * This can sleep, so we can't hold
-		 * the file_list_lock() spinlock.
-		 */
-		mnt_drop_write(mnt);
-		mntput(mnt);
-		goto retry;
+	spin_lock(&inode_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		list_for_each_entry(f, &inode->i_files, f_u.fu_list) {
+			struct vfsmount *mnt;
+			if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
+				continue;
+			if (!file_count(f))
+				continue;
+			if (!(f->f_mode & FMODE_WRITE))
+				continue;
+			f->f_mode &= ~FMODE_WRITE;
+			if (file_check_writeable(f) != 0)
+				continue;
+			file_release_write(f);
+			mnt = mntget(f->f_path.mnt);
+			spin_unlock(&inode_lock);
+			file_list_unlock();
+			/*
+			 * This can sleep, so we can't hold
+			 * the inode_lock spinlock.
+			 */
+			mnt_drop_write(mnt);
+			mntput(mnt);
+			goto retry;
+		}
 	}
+	spin_unlock(&inode_lock);
 	file_list_unlock();
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 562d285..7805d20 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -656,6 +656,7 @@ struct inode {
 	struct list_head	i_list;
 	struct list_head	i_sb_list;
 	struct list_head	i_dentry;
+	struct list_head	i_files;
 	unsigned long		i_ino;
 	atomic_t		i_count;
 	unsigned int		i_nlink;
@@ -878,9 +879,9 @@ struct file {
 	unsigned long f_mnt_write_state;
 #endif
 };
-extern spinlock_t files_lock;
-#define file_list_lock() spin_lock(&files_lock);
-#define file_list_unlock() spin_unlock(&files_lock);
+extern struct mutex files_lock;
+#define file_list_lock() mutex_lock(&files_lock);
+#define file_list_unlock() mutex_unlock(&files_lock);
 
 #define get_file(x)	atomic_long_inc(&(x)->f_count)
 #define file_count(x)	atomic_long_read(&(x)->f_count)
@@ -1277,7 +1278,6 @@ struct super_block {
 	struct list_head	s_io;		/* parked for writeback */
 	struct list_head	s_more_io;	/* parked for more writeback */
 	struct hlist_head	s_anon;		/* anonymous dentries for (nfs) exporting */
-	struct list_head	s_files;
 	/* s_dentry_lru and s_nr_dentry_unused are protected by dcache_lock */
 	struct list_head	s_dentry_lru;	/* unused dentry lru */
 	int			s_nr_dentry_unused;	/* # of dentry on lru */
@@ -2116,7 +2116,7 @@ static inline void insert_inode_hash(struct inode *inode) {
 }
 
 extern struct file * get_empty_filp(void);
-extern void file_move(struct file *f, struct list_head *list);
+extern void file_add(struct file *f, struct list_head *list);
 extern void file_kill(struct file *f);
 #ifdef CONFIG_BLOCK
 struct bio;
-- 
1.6.1.2.350.g88cc

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  parent reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-11 12:01 [RFC][PATCH 0/9] File descriptor hot-unplug support Eric W. Biederman
2009-04-11 12:03 ` [RFC][PATCH 1/9] mm: Introduce remap_file_mappings Eric W. Biederman
2009-04-11 12:05 ` [RFC][PATCH 2/9] mm: Implement generic support for revoking a mapping Eric W. Biederman
2009-04-11 12:06 ` [RFC][PATCH 3/9] sysfs: Use remap_file_mappings Eric W. Biederman
2009-04-11 12:07 ` Eric W. Biederman [this message]
2009-04-11 12:08 ` [RFC][PATCH 5/9] vfs: Introduce basic infrastructure for revoking a file Eric W. Biederman
2009-04-14 22:12   ` Jonathan Corbet
2009-04-15  2:55     ` Eric W. Biederman
2009-04-11 12:10 ` [RFC][PATCH 6/9] vfs: Utilize fops_read_lock where appropriate Eric W. Biederman
2009-04-11 12:11 ` [RFC][PATCH 7/9] vfs: Optimize fops_read_lock Eric W. Biederman
2009-04-11 12:13 ` [RFC][PATCH 8/9] vfs: Implement generic revoked file operations Eric W. Biederman
2009-04-12 18:56   ` Jamie Lokier
2009-04-12 20:04     ` Eric W. Biederman
2009-04-12 20:31       ` Jamie Lokier
2009-04-12 21:53         ` Eric W. Biederman
2009-04-12 20:54       ` Eric W. Biederman
2009-04-12 21:02         ` Jamie Lokier
2009-04-12 23:06           ` Eric W. Biederman
2009-04-11 12:14 ` [RFC][PATCH 9/9] proc: Use the generic vfs revoke facility that now exists Eric W. Biederman
2009-04-11 15:58 ` [RFC][PATCH 0/9] File descriptor hot-unplug support Al Viro
2009-04-11 16:49   ` Eric W. Biederman
2009-04-11 16:56     ` Al Viro
2009-04-11 23:57       ` Eric W. Biederman
2009-04-12 20:21       ` Eric W. Biederman
2009-04-14  3:16 ` Tejun Heo
2009-04-14  7:39   ` Eric W. Biederman
2009-04-14  7:45     ` Tejun Heo
2009-04-14  8:27       ` Eric W. Biederman
2009-04-14  8:49         ` Tejun Heo
2009-04-14 15:07         ` Jamie Lokier
2009-04-14 19:09           ` Eric W. Biederman
2009-06-01 21:45 ` [PATCH 0/23] File descriptor hot-unplug support v2 Eric W. Biederman
2009-06-01 21:50   ` [PATCH 01/23] mm: Introduce revoke_file_mappings Eric W. Biederman
2009-06-01 22:25     ` Andrew Morton
2009-06-02  0:12       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 02/23] vfs: Implement unpoll_file Eric W. Biederman
2009-06-06  8:08     ` Al Viro
2009-06-01 21:50   ` [PATCH 03/23] vfs: Generalize the file_list Eric W. Biederman
2009-06-02  7:06     ` Nick Piggin
2009-06-05 19:33       ` Eric W. Biederman
2009-06-09 10:38         ` Nick Piggin
2009-06-09 18:38           ` Eric W. Biederman
2009-06-10  6:05             ` Nick Piggin
2009-06-01 21:50   ` [PATCH 04/23] vfs: Introduce infrastructure for revoking a file Eric W. Biederman
2009-06-02  5:16     ` Pekka Enberg
2009-06-02  6:51       ` Eric W. Biederman
2009-06-02  7:08         ` Pekka Enberg
2009-06-02  7:14     ` Nick Piggin
2009-06-02 17:06       ` Linus Torvalds
2009-06-02 20:52         ` Eric W. Biederman
2009-06-03  6:37           ` Nick Piggin
2009-06-02 22:56       ` Eric W. Biederman
2009-06-03  6:38         ` Nick Piggin
2009-06-05  9:03     ` Miklos Szeredi
2009-06-05 19:06       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 05/23] vfs: Teach lseek to use file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 06/23] vfs: Teach read/write to use file_hotplug_read_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 07/23] vfs: Teach sendfile,splice,tee,and vmsplice to use file_hotplug_lock Eric W. Biederman
2009-06-03 23:39     ` Badari Pulavarty
2009-06-05 19:37       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 08/23] vfs: Teach readdir " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 09/23] vfs: Teach poll and select " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 10/23] vfs: Teach do_path_lookup " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 11/23] mm: Teach mmap " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 12/23] vfs: Teach fcntl " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 13/23] vfs: Teach ioctl " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 14/23] vfs: Teach flock " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 15/23] vfs: Teach fallocate, and filp_close " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 16/23] vfs: Teach fstatfs, fstatfs64, ftruncate, fchdir, fchmod, fchown " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 17/23] proc: Teach /proc/<pid>/fd " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 18/23] vfs: Teach epoll " Eric W. Biederman
2009-06-02 16:51     ` Davide Libenzi
2009-06-02 21:23       ` Eric W. Biederman
2009-06-02 21:52         ` Davide Libenzi
2009-06-02 22:51           ` Eric W. Biederman
2009-06-03 14:57             ` Davide Libenzi
2009-06-03 20:53               ` Eric W. Biederman
2009-06-04  0:50                 ` Davide Libenzi
2009-06-04  1:42                   ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 19/23] eventpoll: Fix comment Eric W. Biederman
2009-06-01 21:50   ` [PATCH 20/23] vfs: Teach aio to use file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 21/23] vfs: Teach fsync " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 22/23] vfs: Teach fadvice to file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 23/23] vfs: Teach readahead to use the file_hotplug_lock Eric W. Biederman
2009-06-03 23:25     ` Badari Pulavarty
2009-06-06  8:03   ` [PATCH 0/23] File descriptor hot-unplug support v2 Al Viro
2009-06-08  9:41     ` Miklos Szeredi
2009-06-08 10:24       ` Jamie Lokier
2009-06-08 16:29       ` Al Viro
2009-06-08 16:44         ` Miklos Szeredi
2009-06-08 17:50           ` Al Viro
2009-06-08 18:01             ` Linus Torvalds
2009-06-08 18:50               ` Al Viro
2009-06-08 19:18                 ` Linus Torvalds
2009-06-09  6:42                   ` Eric W. Biederman
2009-06-09 10:52                     ` Nick Piggin
2009-06-09  5:50             ` Miklos Szeredi
2009-06-09  6:31               ` Eric W. Biederman
2009-06-09  6:22     ` Eric W. Biederman

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