This is just an example of using the kmem_cache_charge() API. I think it's placed in a place that's applicable for Linus's example [1] although he mentions do_dentry_open() - I have followed from strace() showing openat(2) to path_openat() doing the alloc_empty_file(). The idea is that filp_cachep stops being SLAB_ACCOUNT. Allocations that want to be accounted immediately can use GFP_KERNEL_ACCOUNT. I did that in alloc_empty_file_noaccount() (despite the contradictory name but the noaccount refers to something else, right?) as IIUC it's about kernel-internal opens. alloc_empty_file() is now not doing the accounting, so I added kmem_account_file() that calls the new kmem_cache_charge() API. Why is this unfinished: - there are other callers of alloc_empty_file() which I didn't adjust so they simply became memcg-unaccounted. I haven't investigated for which ones it would make also sense to separate the allocation and accounting. Maybe alloc_empty_file() would need to get a parameter to control this. - I don't know how to properly unwind the accounting failure case. It seems like a new case because when we succeed the open, there's no further error path at least in path_openat(). Basically it boils down I'm unfamiliar with VFS so this depends if this approach is deemed useful enough to finish it. [1] https://lore.kernel.org/all/CAHk-=whYOOdM7jWy5jdrAm8LxcgCMFyk2bt8fYYvZzM4U-zAQA@xxxxxxxxxxxxxx/ Not-signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> --- fs/file_table.c | 9 +++++++-- fs/internal.h | 1 + fs/namei.c | 4 +++- 3 files changed, 11 insertions(+), 3 deletions(-) diff --git a/fs/file_table.c b/fs/file_table.c index b991f90571b4..6401b6f175ae 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -223,6 +223,11 @@ struct file *alloc_empty_file(int flags, const struct cred *cred) return ERR_PTR(-ENFILE); } +int kmem_account_file(struct file *f) +{ + return kmem_cache_charge(filp_cachep, GFP_KERNEL_ACCOUNT, f); +} + /* * Variant of alloc_empty_file() that doesn't check and modify nr_files. * @@ -234,7 +239,7 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred) struct file *f; int error; - f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL); + f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL_ACCOUNT); if (unlikely(!f)) return ERR_PTR(-ENOMEM); @@ -468,7 +473,7 @@ void __init files_init(void) { filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, SLAB_TYPESAFE_BY_RCU | SLAB_HWCACHE_ALIGN | - SLAB_PANIC | SLAB_ACCOUNT, NULL); + SLAB_PANIC, NULL); percpu_counter_init(&nr_files, 0, GFP_KERNEL); } diff --git a/fs/internal.h b/fs/internal.h index b67406435fc0..06ada11b71d0 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -96,6 +96,7 @@ extern void chroot_fs_refs(const struct path *, const struct path *); struct file *alloc_empty_file(int flags, const struct cred *cred); struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred); struct file *alloc_empty_backing_file(int flags, const struct cred *cred); +int kmem_account_file(struct file *file); static inline void file_put_write_access(struct file *file) { diff --git a/fs/namei.c b/fs/namei.c index 4e0de939fea1..fcf3f3fcd059 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3799,8 +3799,10 @@ static struct file *path_openat(struct nameidata *nd, terminate_walk(nd); } if (likely(!error)) { - if (likely(file->f_mode & FMODE_OPENED)) + if (likely(file->f_mode & FMODE_OPENED)) { + kmem_account_file(file); return file; + } WARN_ON(1); error = -EINVAL; } -- 2.44.0
