Sasha, just be aware that this commit was added to help tracking down a particular syzbot report. As such there's no point in carrying it in -stable but there's no big harm either... Just one patch more. Honza On Thu 25-03-21 07:24:18, Sasha Levin wrote: > From: Jan Kara <jack@xxxxxxx> > > [ Upstream commit 163f0ec1df33cf468509ff38cbcbb5eb0d7fac60 ] > > 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@xxxxxxxxxx/ > Signed-off-by: Jan Kara <jack@xxxxxxx> > Link: https://lore.kernel.org/r/20210222171626.21884-1-jack@xxxxxxx > Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > fs/ext4/xattr.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index 372208500f4e..083c95126781 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -1462,6 +1462,9 @@ ext4_xattr_inode_cache_find(struct inode *inode, const void *value, > if (!ce) > return NULL; > > + WARN_ON_ONCE(ext4_handle_valid(journal_current_handle()) && > + !(current->flags & PF_MEMALLOC_NOFS)); > + > ea_data = kvmalloc(value_len, GFP_KERNEL); > if (!ea_data) { > mb_cache_entry_put(ea_inode_cache, ce); > @@ -2327,6 +2330,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index, > error = -ENOSPC; > goto cleanup; > } > + WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS)); > } > > error = ext4_reserve_inode_write(handle, inode, &is.iloc); > -- > 2.30.1 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
