On 09/14/2010 04:02 PM, Nathan Lynch wrote: > Large page-backed shm regions require special handling, especially > during restart. The association of a large page with a shm region's > inode can occur only in the context of a process causing a fault with > the region mapped into its mm. In order to restore that association, > temporarily shmat-attach the restored SHM_HUGETLB region to the > restarting process's mm, using the just-restored ipc namespace > instead of the current one (the nsproxy switch hasn't occured yet). > > Since the temporary shmat of the region during restart causes some of > the shm attributes to be updated, re-restore them from the ipc_shm > checkpoint header after unmapping.
Would it work to just move the original call to load_ipc_shm_hdr() further down in restore_ipc_shm(), especially since the mutex is not needed anymore - that way you don't need to re-restore them ? I'm not too familiar with HUGETLB code otherwise, so hoping that others review those parts while I find time to study it ... Thanks, Oren. > > Signed-off-by: Nathan Lynch <[email protected]> > --- > ipc/checkpoint_shm.c | 154 > ++++++++++++++++++++++++++++++++++++++++++++++---- > 1 files changed, 142 insertions(+), 12 deletions(-) > > diff --git a/ipc/checkpoint_shm.c b/ipc/checkpoint_shm.c > index 69ba35a..7f9d701 100644 > --- a/ipc/checkpoint_shm.c > +++ b/ipc/checkpoint_shm.c > @@ -32,6 +32,69 @@ > * ipc checkpoint > */ > > +#define CKPT_HDR_HPAGE_LAST ~(0UL) > +static bool ckpt_hdr_hpage_last(const struct ckpt_hdr_hpage *hdr) > +{ > + return hdr->index == CKPT_HDR_HPAGE_LAST; > +} > + > +static void ckpt_hdr_hpage_init(struct ckpt_hdr_hpage *hdr, unsigned long > shift) > +{ > + hdr->h.type = CKPT_HDR_HPAGE; > + hdr->h.len = sizeof(struct ckpt_hdr_hpage); > + hdr->shift = shift; > + hdr->index = 0; /* to be filled in by user */ > +} > + > +static int shm_hugetlb_checkpoint_contents(struct ckpt_ctx *ctx, struct file > *filp) > +{ > + struct hstate *h = hstate_file(filp); > + struct address_space *mapping = filp->f_mapping; > + struct inode *inode = mapping->host; > + struct ckpt_hdr_hpage hdr; > + unsigned long end_index; > + unsigned long index; > + ssize_t retval = 0; > + loff_t isize; > + > + isize = i_size_read(inode); > + if (isize == 0) > + goto out; > + > + end_index = (isize - 1) >> huge_page_shift(h); > + > + ckpt_hdr_hpage_init(&hdr, huge_page_shift(h)); > + > + for (index = 0; index < end_index + 1; index++) { > + struct page *page; > + > + page = find_get_page(mapping, index); > + > + /* skip holes */ > + if (!page) > + continue; > + > + hdr.index = index; > + > + retval = ckpt_write_obj(ctx, &hdr.h); > + if (retval < 0) > + goto release; > + > + retval = hugetlb_checkpoint_page(ctx, page); > +release: > + page_cache_release(page); > + if (retval < 0) > + break; > + } > + > + if (retval < 0) > + goto out; > + hdr.index = CKPT_HDR_HPAGE_LAST; > + retval = ckpt_write_obj(ctx, &hdr.h); > +out: > + return retval; > +} > + > /* called with the msgids->rw_mutex is read-held */ > static int fill_ipc_shm_hdr(struct ckpt_ctx *ctx, > struct ckpt_hdr_ipc_shm *h, > @@ -59,10 +122,8 @@ static int fill_ipc_shm_hdr(struct ckpt_ctx *ctx, > > h->flags = 0; > > - /* check if shm was setup with SHM_HUGETLB (unsupported yet) */ > if (is_file_hugepages(shp->shm_file)) { > - pr_warning("c/r: unsupported SHM_HUGETLB\n"); > - ret = -ENOSYS; > + h->flags |= SHM_HUGETLB; > } else { > struct shmem_inode_info *info; > > @@ -117,7 +178,10 @@ int checkpoint_ipc_shm(int id, void *p, void *data) > if (ret < 0) > goto out; > > - ret = checkpoint_memory_contents(ctx, NULL, inode); > + if (is_file_hugepages(shp->shm_file)) > + ret = shm_hugetlb_checkpoint_contents(ctx, shp->shm_file); > + else > + ret = checkpoint_memory_contents(ctx, NULL, inode); > out: > ckpt_hdr_put(ctx, h); > return ret; > @@ -149,6 +213,75 @@ struct dq_ipcshm_del { > int id; > }; > > +static void __load_ipc_shm_hdr(const struct ckpt_hdr_ipc_shm *h, struct > shmid_kernel *shp) > +{ > + shp->shm_atim = h->shm_atim; > + shp->shm_dtim = h->shm_dtim; > + shp->shm_ctim = h->shm_ctim; > + shp->shm_cprid = h->shm_cprid; > + shp->shm_lprid = h->shm_lprid; > +} > + > +static int shm_hugetlb_restore_contents(struct ckpt_ctx *ctx, struct > ipc_namespace *ipcns, struct shmid_kernel *shp, const struct ckpt_hdr_ipc_shm > *hdr) > +{ > + unsigned long start; > + int ret; > + > + ret = do_shmat_ns_pgoff(ipcns, shp->shm_perm.id, (char __user *)0, > + 0, &start, 0, 0); > + if (ret != 0) > + return ret; > + > + ckpt_debug("temporarily using %#lx for huge shm restore\n", start); > + > + while (1) { > + struct ckpt_hdr_hpage *hdr; > + unsigned long hpagesize; > + unsigned long index; > + unsigned long addr; > + struct page *page; > + bool last; > + > + hdr = ckpt_read_obj_type(ctx, sizeof(*hdr), CKPT_HDR_HPAGE); > + if (IS_ERR(hdr)) { > + ret = PTR_ERR(hdr); > + break; > + } > + > + last = ckpt_hdr_hpage_last(hdr); > + index = (unsigned long)hdr->index; > + hpagesize = 1UL << hdr->shift; > + > + ckpt_hdr_put(ctx, hdr); > + > + if (last) > + break; > + > + addr = start + (hpagesize * index); > + > + down_read(¤t->mm->mmap_sem); > + ret = get_user_pages(current, current->mm, addr, 1, 1, 1, > + &page, NULL); > + up_read(¤t->mm->mmap_sem); > + > + if (ret < 0) > + break; > + > + ret = hugetlb_restore_page(ctx, page); > + > + page_cache_release(page); > + > + if (ret < 0) > + break; > + } > + > + sys_shmdt((void __user *)start); > + > + __load_ipc_shm_hdr(hdr, shp); > + > + return ret; > +} > + > static int _ipc_shm_delete(struct ipc_namespace *ns, int id) > { > mm_segment_t old_fs; > @@ -190,11 +323,7 @@ static int load_ipc_shm_hdr(struct ckpt_ctx *ctx, > if (h->shm_cprid < 0 || h->shm_lprid < 0) > return -EINVAL; > > - shp->shm_atim = h->shm_atim; > - shp->shm_dtim = h->shm_dtim; > - shp->shm_ctim = h->shm_ctim; > - shp->shm_cprid = h->shm_cprid; > - shp->shm_lprid = h->shm_lprid; > + __load_ipc_shm_hdr(h, shp); > > return 0; > } > @@ -224,8 +353,6 @@ int restore_ipc_shm(struct ckpt_ctx *ctx, struct > ipc_namespace *ns) > ret = -ENOSYS; > if (h->mlock_uid != (unsigned int) -1) /* FIXME: support SHM_LOCK */ > goto out; > - if (h->flags & SHM_HUGETLB) /* FIXME: support SHM_HUGETLB */ > - goto out; > > shmflag = h->flags | h->perms.mode | IPC_CREAT | IPC_EXCL; > ckpt_debug("shm: do_shmget size %lld flag %#x id %d\n", > @@ -294,7 +421,10 @@ int restore_ipc_shm(struct ckpt_ctx *ctx, struct > ipc_namespace *ns) > ret = ckpt_obj_insert(ctx, file, h->objref, CKPT_OBJ_FILE); > if (ret < 0) > goto fput; > - ret = restore_memory_contents(ctx, file->f_dentry->d_inode); > + if (is_file_hugepages(file)) > + ret = shm_hugetlb_restore_contents(ctx, ns, shp, h); > + else > + ret = restore_memory_contents(ctx, file->f_dentry->d_inode); > fput: > fput(file); > _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
