This is a note to let you know that I've just added the patch titled
fuse: fix deadlock between atomic O_TRUNC and page invalidation
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fuse-fix-deadlock-between-atomic-o_trunc-and-page-in.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6a8e4273ffe4f780a39f1c0677b80a21e832dc9d
Author: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Date: Fri Apr 22 15:48:53 2022 +0200
fuse: fix deadlock between atomic O_TRUNC and page invalidation
[ Upstream commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b ]
fuse_finish_open() will be called with FUSE_NOWRITE set in case of atomic
O_TRUNC open(), so commit 76224355db75 ("fuse: truncate pagecache on
atomic_o_trunc") replaced invalidate_inode_pages2() by truncate_pagecache()
in such a case to avoid the A-A deadlock. However, we found another A-B-B-A
deadlock related to the case above, which will cause the xfstests
generic/464 testcase hung in our virtio-fs test environment.
For example, consider two processes concurrently open one same file, one
with O_TRUNC and another without O_TRUNC. The deadlock case is described
below, if open(O_TRUNC) is already set_nowrite(acquired A), and is trying
to lock a page (acquiring B), open() could have held the page lock
(acquired B), and waiting on the page writeback (acquiring A). This would
lead to deadlocks.
open(O_TRUNC)
----------------------------------------------------------------
fuse_open_common
inode_lock [C acquire]
fuse_set_nowrite [A acquire]
fuse_finish_open
truncate_pagecache
lock_page [B acquire]
truncate_inode_page
unlock_page [B release]
fuse_release_nowrite [A release]
inode_unlock [C release]
----------------------------------------------------------------
open()
----------------------------------------------------------------
fuse_open_common
fuse_finish_open
invalidate_inode_pages2
lock_page [B acquire]
fuse_launder_page
fuse_wait_on_page_writeback [A acquire & release]
unlock_page [B release]
----------------------------------------------------------------
Besides this case, all calls of invalidate_inode_pages2() and
invalidate_inode_pages2_range() in fuse code also can deadlock with
open(O_TRUNC).
Fix by moving the truncate_pagecache() call outside the nowrite protected
region. The nowrite protection is only for delayed writeback
(writeback_cache) case, where inode lock does not protect against
truncation racing with writes on the server. Write syscalls racing with
page cache truncation still get the inode lock protection.
This patch also changes the order of filemap_invalidate_lock()
vs. fuse_set_nowrite() in fuse_open_common(). This new order matches the
order found in fuse_file_fallocate() and fuse_do_setattr().
Reported-by: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx>
Tested-by: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx>
Fixes: e4648309b85a ("fuse: truncate pending writes on O_TRUNC")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 74303d6e987b..a93d675a726a 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -537,6 +537,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
struct fuse_file *ff;
void *security_ctx = NULL;
u32 security_ctxlen;
+ bool trunc = flags & O_TRUNC;
/* Userspace expects S_IFREG in create mode */
BUG_ON((mode & S_IFMT) != S_IFREG);
@@ -561,7 +562,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
inarg.mode = mode;
inarg.umask = current_umask();
- if (fm->fc->handle_killpriv_v2 && (flags & O_TRUNC) &&
+ if (fm->fc->handle_killpriv_v2 && trunc &&
!(flags & O_EXCL) && !capable(CAP_FSETID)) {
inarg.open_flags |= FUSE_OPEN_KILL_SUIDGID;
}
@@ -623,6 +624,10 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
} else {
file->private_data = ff;
fuse_finish_open(inode, file);
+ if (fm->fc->atomic_o_trunc && trunc)
+ truncate_pagecache(inode, 0);
+ else if (!(ff->open_flags & FOPEN_KEEP_CACHE))
+ invalidate_inode_pages2(inode->i_mapping);
}
return err;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 60885ff9157c..dfee142bca5c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -210,13 +210,9 @@ void fuse_finish_open(struct inode *inode, struct file *file)
fi->attr_version = atomic64_inc_return(&fc->attr_version);
i_size_write(inode, 0);
spin_unlock(&fi->lock);
- truncate_pagecache(inode, 0);
file_update_time(file);
fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
- } else if (!(ff->open_flags & FOPEN_KEEP_CACHE)) {
- invalidate_inode_pages2(inode->i_mapping);
}
-
if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
fuse_link_write_file(file);
}
@@ -239,30 +235,38 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
if (err)
return err;
- if (is_wb_truncate || dax_truncate) {
+ if (is_wb_truncate || dax_truncate)
inode_lock(inode);
- fuse_set_nowrite(inode);
- }
if (dax_truncate) {
filemap_invalidate_lock(inode->i_mapping);
err = fuse_dax_break_layouts(inode, 0, 0);
if (err)
- goto out;
+ goto out_inode_unlock;
}
+ if (is_wb_truncate || dax_truncate)
+ fuse_set_nowrite(inode);
+
err = fuse_do_open(fm, get_node_id(inode), file, isdir);
if (!err)
fuse_finish_open(inode, file);
-out:
+ if (is_wb_truncate || dax_truncate)
+ fuse_release_nowrite(inode);
+ if (!err) {
+ struct fuse_file *ff = file->private_data;
+
+ if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC))
+ truncate_pagecache(inode, 0);
+ else if (!(ff->open_flags & FOPEN_KEEP_CACHE))
+ invalidate_inode_pages2(inode->i_mapping);
+ }
if (dax_truncate)
filemap_invalidate_unlock(inode->i_mapping);
-
- if (is_wb_truncate | dax_truncate) {
- fuse_release_nowrite(inode);
+out_inode_unlock:
+ if (is_wb_truncate || dax_truncate)
inode_unlock(inode);
- }
return err;
}
