From: Jan Kara Date: Tue, 12 Jun 2012 14:20:30 +0000 (+0200) Subject: fs: Push mnt_want_write() outside of i_mutex X-Git-Tag: v3.6-rc1~18^2~20 X-Git-Url: http://pileus.org/git/?a=commitdiff_plain;h=c30dabfe5d10c5fd70d882e5afb8f59f2942b194;p=~andy%2Flinux 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 Signed-off-by: Al Viro --- 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);