Remove BKL from remote_llseek v2

PATCH In review Andi Kleen 2 participants 2 messages Jun 27, 2008

Subsystems (3)

VFS NFS client GFS2 file system

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Andi Kleen

author

2008-06-27 09:06 UTC #0 lore raw

PATCH 1/1 Remove BKL from remote_llseek v2

Remove BKL from remote_llseek v2

Andrew, can you please consider this patch for -mm? I sent it to Jonathan earlier, but he ignored it.

It passed review by a few folks in the v1 form.

Thanks,

-Andi

---

- 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 [email protected]

Signed-off-by Andi Kleen <[email protected]>

---
 fs/cifs/cifsfs.c   |    2 +-
 fs/gfs2/ops_file.c |    4 ++--
 fs/ncpfs/file.c    |   12 +++++++++++-
 fs/nfs/file.c      |    6 +++++-
 fs/read_write.c    |   38 +++++++++++---------------------------
 fs/smbfs/file.c    |   11 ++++++++++-
 include/linux/fs.h |    3 ++-
 7 files changed, 42 insertions(+), 34 deletions(-)

fs/cifs/cifsfs.c +1 -1

Index: linux/fs/cifs/cifsfs.c
===================================================================
@@ -613,7 +613,7 @@ static loff_t cifs_llseek(struct file *f
 		if (retval < 0)
 			return (loff_t)retval;
 	}
-	return remote_llseek(file, offset, origin);
+	return generic_file_llseek_unlocked(file, offset, origin);
 }
 
 struct file_system_type cifs_fs_type = {

fs/gfs2/ops_file.c +2 -2

Index: linux/fs/gfs2/ops_file.c
===================================================================
@@ -62,11 +62,11 @@ static loff_t gfs2_llseek(struct file *f
 		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
 					   &i_gh);
 		if (!error) {
-			error = remote_llseek(file, offset, origin);
+			error = generic_file_llseek_unlocked(file, offset, origin);
 			gfs2_glock_dq_uninit(&i_gh);
 		}
 	} else
-		error = remote_llseek(file, offset, origin);
+		error = generic_file_llseek_unlocked(file, offset, origin);
 
 	return error;
 }

fs/ncpfs/file.c +11 -1

Index: linux/fs/ncpfs/file.c
===================================================================
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/sched.h>
+#include <linux/smp_lock.h>
 
 #include <linux/ncp_fs.h>
 #include "ncplib_kernel.h"

@@ -281,9 +282,18 @@ static int ncp_release(struct inode *ino
 	return 0;
 }
 
+static loff_t ncp_remote_llseek(struct file *file, loff_t offset, int origin)
+{
+	loff_t ret;
+	lock_kernel();
+	ret = generic_file_llseek_unlocked(file, offset, origin);
+	unlock_kernel();
+	return ret;
+}
+
 const struct file_operations ncp_file_operations =
 {
-	.llseek		= remote_llseek,
+	.llseek 	= ncp_remote_llseek,
 	.read		= ncp_file_read,
 	.write		= ncp_file_write,
 	.ioctl		= ncp_ioctl,

fs/read_write.c +11 ~~-27~~

Index: linux/fs/read_write.c
===================================================================
@@ -31,12 +31,12 @@ const struct file_operations generic_ro_
 
 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 *
 	}
 	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)
 {

fs/smbfs/file.c +10 -1

Index: linux/fs/smbfs/file.c
===================================================================
@@ -422,9 +422,18 @@ smb_file_permission(struct inode *inode,
 	return error;
 }
 
+static loff_t smb_remote_llseek(struct file *file, loff_t offset, int origin)
+{
+	loff_t ret;
+	lock_kernel();
+	ret = generic_file_llseek_unlocked(file, offset, origin);
+	unlock_kernel();
+	return ret;
+}
+
 const struct file_operations smb_file_operations =
 {
-	.llseek		= remote_llseek,
+	.llseek 	= smb_remote_llseek,
 	.read		= do_sync_read,
 	.aio_read	= smb_file_aio_read,
 	.write		= do_sync_write,

include/linux/fs.h +2 -1

Index: linux/include/linux/fs.h
===================================================================
@@ -1871,7 +1871,8 @@ extern void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
 extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
-extern loff_t remote_llseek(struct file *file, loff_t offset, int origin);
+extern loff_t generic_file_llseek_unlocked(struct file *file, loff_t offset,
+			int origin);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);

fs/nfs/file.c +5 -1

Index: linux/fs/nfs/file.c
===================================================================
@@ -170,6 +170,7 @@ force_reval:
 
 static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
 {
+	loff_t loff;
 	/* origin == SEEK_END => we must revalidate the cached file length */
 	if (origin == SEEK_END) {
 		struct inode *inode = filp->f_mapping->host;

@@ -177,7 +178,10 @@ static loff_t nfs_file_llseek(struct fil
 		if (retval < 0)
 			return (loff_t)retval;
 	}
-	return remote_llseek(filp, offset, origin);
+	lock_kernel();	/* BKL needed? */
+	loff = generic_file_llseek_unlocked(filp, offset, origin);
+	unlock_kernel();
+	return loff;
 }
 
 /*

Jonathan Corbet

2008-06-27 13:18 UTC #1 lore raw

Quoted 2 lines · On Fri, 27 Jun 2008 11:05:24 +0200 Andi Kleen <[email protected]> wrote:

Andrew, can you please consider this patch for -mm? I sent it to Jonathan earlier, but he ignored it.

Hmm, I sure didn't do that deliberately. My apologies if it fell through the cracks. Ah, I see, I had set it aside with the fasync stuff, sorry.

I can pull it into the BKL-removal tree, certainly. Better late than never?

jon