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Subject[PATCH 3.0-stable] Revert "sysfs: fix race between readdir and lseek"
This reverts commit 991f76f837bf22c5bb07261cfd86525a0a96650c in Linus' 
tree which is f366c8f271888f48e15cc7c0ab70f184c220c8a4 in
linux-stable.git

It depends on ef3d0fd27e90f ("vfs: do (nearly) lockless generic_file_llseek")
which is available only in 3.2+.

When applied on 3.0 codebase, it causes A-A deadlock, whenever anyone does
seek() on sysfs, as both generic_file_llseek() and sysfs_dir_llseek() obtain
i_mutex.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
fs/sysfs/dir.c | 13 +------------
1 files changed, 1 insertions(+), 12 deletions(-)

Index: linux-3.0-SLE11-SP3-sysfs-hang-debug/fs/sysfs/dir.c
===================================================================
--- linux-3.0-SLE11-SP3-sysfs-hang-debug.orig/fs/sysfs/dir.c
+++ linux-3.0-SLE11-SP3-sysfs-hang-debug/fs/sysfs/dir.c
@@ -961,21 +961,9 @@ static int sysfs_readdir(struct file * f
return 0;
}

-static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence)
-{
- struct inode *inode = file->f_path.dentry->d_inode;
- loff_t ret;
-
- mutex_lock(&inode->i_mutex);
- ret = generic_file_llseek(file, offset, whence);
- mutex_unlock(&inode->i_mutex);
-
- return ret;
-}
-
const struct file_operations sysfs_dir_operations = {
.read = generic_read_dir,
.readdir = sysfs_readdir,
.release = sysfs_dir_release,
- .llseek = sysfs_dir_llseek,
+ .llseek = generic_file_llseek,
};
--
Jiri Kosina
SUSE Labs


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