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authorJan Kara <jack@suse.cz>2012-06-12 16:20:30 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-31 01:02:49 +0400
commitc30dabfe5d10c5fd70d882e5afb8f59f2942b194 (patch)
tree2a643a825fb91a1ae48c5673a9f5fcba891b6122 /fs
parent4fcf1c6205fcfc7a226a144ae4d83b7f5415cab8 (diff)
fs: Push mnt_want_write() outside of i_mutex
Currently, mnt_want_write() is sometimes called with i_mutex held and sometimes without it. This isn't really a problem because mnt_want_write() is a non-blocking operation (essentially has a trylock semantics) but when the function starts to handle also frozen filesystems, it will get a full lock semantics and thus proper lock ordering has to be established. So move all mnt_want_write() calls outside of i_mutex. One non-trivial case needing conversion is kern_path_create() / user_path_create() which didn't include mnt_want_write() but now needs to because it acquires i_mutex. Because there are virtual file systems which don't bother with freeze / remount-ro protection we actually provide both versions of the function - one which calls mnt_want_write() and one which does not. [AV: scratch the previous, mnt_want_write() has been moved to kern_path_create() by now] Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/namei.c46
1 files changed, 25 insertions, 21 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 35291ac6f42..1b464390dde 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2975,6 +2975,7 @@ struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path
{
struct dentry *dentry = ERR_PTR(-EEXIST);
struct nameidata nd;
+ int err2;
int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
if (error)
return ERR_PTR(error);
@@ -2988,6 +2989,8 @@ struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path
nd.flags &= ~LOOKUP_PARENT;
nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
+ /* don't fail immediately if it's r/o, at least try to report other errors */
+ err2 = mnt_want_write(nd.path.mnt);
/*
* Do the final lookup.
*/
@@ -3009,9 +3012,10 @@ struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path
error = -ENOENT;
goto fail;
}
- error = mnt_want_write(nd.path.mnt);
- if (error)
+ if (unlikely(err2)) {
+ error = err2;
goto fail;
+ }
*path = nd.path;
return dentry;
fail:
@@ -3019,6 +3023,8 @@ fail:
dentry = ERR_PTR(error);
unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ if (!err2)
+ mnt_drop_write(nd.path.mnt);
out:
path_put(&nd.path);
return dentry;
@@ -3266,6 +3272,9 @@ static long do_rmdir(int dfd, const char __user *pathname)
}
nd.flags &= ~LOOKUP_PARENT;
+ error = mnt_want_write(nd.path.mnt);
+ if (error)
+ goto exit1;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
@@ -3276,19 +3285,15 @@ static long do_rmdir(int dfd, const char __user *pathname)
error = -ENOENT;
goto exit3;
}
- error = mnt_want_write(nd.path.mnt);
- if (error)
- goto exit3;
error = security_path_rmdir(&nd.path, dentry);
if (error)
- goto exit4;
+ goto exit3;
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
-exit4:
- mnt_drop_write(nd.path.mnt);
exit3:
dput(dentry);
exit2:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
@@ -3355,6 +3360,9 @@ static long do_unlinkat(int dfd, const char __user *pathname)
goto exit1;
nd.flags &= ~LOOKUP_PARENT;
+ error = mnt_want_write(nd.path.mnt);
+ if (error)
+ goto exit1;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
@@ -3367,21 +3375,17 @@ static long do_unlinkat(int dfd, const char __user *pathname)
if (!inode)
goto slashes;
ihold(inode);
- error = mnt_want_write(nd.path.mnt);
- if (error)
- goto exit2;
error = security_path_unlink(&nd.path, dentry);
if (error)
- goto exit3;
+ goto exit2;
error = vfs_unlink(nd.path.dentry->d_inode, dentry);
-exit3:
- mnt_drop_write(nd.path.mnt);
- exit2:
+exit2:
dput(dentry);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (inode)
iput(inode); /* truncate the inode here */
+ mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
@@ -3753,6 +3757,10 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
if (newnd.last_type != LAST_NORM)
goto exit2;
+ error = mnt_want_write(oldnd.path.mnt);
+ if (error)
+ goto exit2;
+
oldnd.flags &= ~LOOKUP_PARENT;
newnd.flags &= ~LOOKUP_PARENT;
newnd.flags |= LOOKUP_RENAME_TARGET;
@@ -3788,23 +3796,19 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
if (new_dentry == trap)
goto exit5;
- error = mnt_want_write(oldnd.path.mnt);
- if (error)
- goto exit5;
error = security_path_rename(&oldnd.path, old_dentry,
&newnd.path, new_dentry);
if (error)
- goto exit6;
+ goto exit5;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
-exit6:
- mnt_drop_write(oldnd.path.mnt);
exit5:
dput(new_dentry);
exit4:
dput(old_dentry);
exit3:
unlock_rename(new_dir, old_dir);
+ mnt_drop_write(oldnd.path.mnt);
exit2:
path_put(&newnd.path);
putname(to);