0229b5926d
commit 163f0ec1df33cf468509ff38cbcbb5eb0d7fac60 upstream. Syzbot is reporting that ext4 can enter fs reclaim from kvmalloc() while the transaction is started like: fs_reclaim_acquire+0x117/0x150 mm/page_alloc.c:4340 might_alloc include/linux/sched/mm.h:193 [inline] slab_pre_alloc_hook mm/slab.h:493 [inline] slab_alloc_node mm/slub.c:2817 [inline] __kmalloc_node+0x5f/0x430 mm/slub.c:4015 kmalloc_node include/linux/slab.h:575 [inline] kvmalloc_node+0x61/0xf0 mm/util.c:587 kvmalloc include/linux/mm.h:781 [inline] ext4_xattr_inode_cache_find fs/ext4/xattr.c:1465 [inline] ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1508 [inline] ext4_xattr_set_entry+0x1ce6/0x3780 fs/ext4/xattr.c:1649 ext4_xattr_ibody_set+0x78/0x2b0 fs/ext4/xattr.c:2224 ext4_xattr_set_handle+0x8f4/0x13e0 fs/ext4/xattr.c:2380 ext4_xattr_set+0x13a/0x340 fs/ext4/xattr.c:2493 This should be impossible since transaction start sets PF_MEMALLOC_NOFS. Add some assertions to the code to catch if something isn't working as expected early. Link: https://lore.kernel.org/linux-ext4/000000000000563a0205bafb7970@google.com/ Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20210222171626.21884-1-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.