Hello, On Sun, Jan 29, 2023 at 09:26:57PM +0000, Matthew Wilcox wrote: > > > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c > > > index e78be66bbf01..a4e76f96f291 100644 > > > --- a/fs/crypto/crypto.c > > > +++ b/fs/crypto/crypto.c > > > @@ -205,6 +205,9 @@ struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, > > > } > > > SetPagePrivate(ciphertext_page); > > > set_page_private(ciphertext_page, (unsigned long)page); > > > +#ifdef CONFIG_MEMCG > > > + ciphertext_page->memcg_data = page->memcg_data; > > > +#endif > > > return ciphertext_page; > > > } > > > > Nothing outside mm/ and include/linux/memcontrol.h does anything with memcg_data > > directly. Are you sure this is the right thing to do here? > > Nope ;-) Happy to hear from people who know more about cgroups than I > do. Adding some more ccs. > > > Also, this patch causes the following: > > Oops. Clearly memcg_data needs to be set to NULL before we free it. These can usually be handled by explicitly associating the bio's to the desired cgroups using one of bio_associate_blkg*() or bio_clone_blkg_association(). It is possible to go through memcg ownership too using set_active_memcg() so that the page is owned by the target cgroup; however, the page ownership doesn't directly map to IO ownership as the relationship depends on the type of the page (e.g. IO ownership for pagecache writeback is determined per-inode, not per-page). If the in-flight pages are limited, it probably is better to set bio association directly. Thanks. -- tejun
