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Wed, 25 Nov 2020 15:13:25 -0800 (PST) Date: Wed, 25 Nov 2020 15:13:22 -0800 From: Minchan Kim To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, mhocko@kernel.org, mhocko@suse.com, rientjes@google.com, willy@infradead.org, hannes@cmpxchg.org, guro@fb.com, riel@surriel.com, christian@brauner.io, oleg@redhat.com, timmurray@google.com, linux-api@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/2] mm/madvise: allow process_madvise operations on entire memory range Message-ID: <20201125231322.GF1484898@google.com> References: <20201124053943.1684874-1-surenb@google.com> <20201124053943.1684874-2-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201124053943.1684874-2-surenb@google.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 23, 2020 at 09:39:42PM -0800, Suren Baghdasaryan wrote: > process_madvise requires a vector of address ranges to be provided for > its operations. When an advice should be applied to the entire process, > the caller process has to obtain the list of VMAs of the target process > by reading the /proc/pid/maps or some other way. The cost of this > operation grows linearly with increasing number of VMAs in the target > process. Even constructing the input vector can be non-trivial when > target process has several thousands of VMAs and the syscall is being > issued during high memory pressure period when new allocations for such > a vector would only worsen the situation. > In the case when advice is being applied to the entire memory space of > the target process, this creates an extra overhead. > Add PMADV_FLAG_RANGE flag for process_madvise enabling the caller to > advise a memory range of the target process. For now, to keep it simple, > only the entire process memory range is supported, vec and vlen inputs > in this mode are ignored and can be NULL and 0. > Instead of returning the number of bytes that advice was successfully > applied to, the syscall in this mode returns 0 on success. This is due > to the fact that the number of bytes would not be useful for the caller > that does not know the amount of memory the call is supposed to affect. > Besides, the ssize_t return type can be too small to hold the number of > bytes affected when the operation is applied to a large memory range. Can we just use one element in iovec to indicate entire address rather than using up the reserved flags? struct iovec { .iov_base = NULL, .iov_len = (~(size_t)0), }; Furthermore, it would be applied for other syscalls where have support iovec if we agree on it. > > Signed-off-by: Suren Baghdasaryan > --- > arch/alpha/include/uapi/asm/mman.h | 4 ++ > arch/mips/include/uapi/asm/mman.h | 4 ++ > arch/parisc/include/uapi/asm/mman.h | 4 ++ > arch/xtensa/include/uapi/asm/mman.h | 4 ++ > fs/io_uring.c | 2 +- > include/linux/mm.h | 3 +- > include/uapi/asm-generic/mman-common.h | 4 ++ > mm/madvise.c | 47 +++++++++++++++++--- > tools/include/uapi/asm-generic/mman-common.h | 4 ++ > 9 files changed, 67 insertions(+), 9 deletions(-) > > diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h > index a18ec7f63888..54588d2f5406 100644 > --- a/arch/alpha/include/uapi/asm/mman.h > +++ b/arch/alpha/include/uapi/asm/mman.h > @@ -79,4 +79,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* __ALPHA_MMAN_H__ */ > diff --git a/arch/mips/include/uapi/asm/mman.h b/arch/mips/include/uapi/asm/mman.h > index 57dc2ac4f8bd..af94f38a3a9d 100644 > --- a/arch/mips/include/uapi/asm/mman.h > +++ b/arch/mips/include/uapi/asm/mman.h > @@ -106,4 +106,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* _ASM_MMAN_H */ > diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h > index ab78cba446ed..ae644c493991 100644 > --- a/arch/parisc/include/uapi/asm/mman.h > +++ b/arch/parisc/include/uapi/asm/mman.h > @@ -77,4 +77,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* __PARISC_MMAN_H__ */ > diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h > index e5e643752947..934cdd11abff 100644 > --- a/arch/xtensa/include/uapi/asm/mman.h > +++ b/arch/xtensa/include/uapi/asm/mman.h > @@ -114,4 +114,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* _XTENSA_MMAN_H */ > diff --git a/fs/io_uring.c b/fs/io_uring.c > index a8c136a1cf4e..508c48b998ee 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -4118,7 +4118,7 @@ static int io_madvise(struct io_kiocb *req, bool force_nonblock) > if (force_nonblock) > return -EAGAIN; > > - ret = do_madvise(current->mm, ma->addr, ma->len, ma->advice); > + ret = do_madvise(current->mm, ma->addr, ma->len, ma->advice, 0); > if (ret < 0) > req_set_fail_links(req); > io_req_complete(req, ret); > diff --git a/include/linux/mm.h b/include/linux/mm.h > index db6ae4d3fb4e..414c7639e394 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2579,7 +2579,8 @@ extern int __do_munmap(struct mm_struct *, unsigned long, size_t, > struct list_head *uf, bool downgrade); > extern int do_munmap(struct mm_struct *, unsigned long, size_t, > struct list_head *uf); > -extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior); > +extern int do_madvise(struct mm_struct *mm, unsigned long start, unsigned long len_in, > + int behavior, unsigned int flags); > > #ifdef CONFIG_MMU > extern int __mm_populate(unsigned long addr, unsigned long len, > diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h > index f94f65d429be..4898034593ec 100644 > --- a/include/uapi/asm-generic/mman-common.h > +++ b/include/uapi/asm-generic/mman-common.h > @@ -80,4 +80,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* __ASM_GENERIC_MMAN_COMMON_H */ > diff --git a/mm/madvise.c b/mm/madvise.c > index a8d8d48a57fe..1aa074a46524 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1001,6 +1001,14 @@ process_madvise_behavior_valid(int behavior) > } > } > > +static bool can_range_madv_lru_vma(struct vm_area_struct *vma, int behavior) > +{ > + if (!can_madv_lru_vma(vma)) > + return false; > + > + return true; > +} > + > /* > * The madvise(2) system call. > * > @@ -1067,15 +1075,21 @@ process_madvise_behavior_valid(int behavior) > * -EBADF - map exists, but area maps something that isn't a file. > * -EAGAIN - a kernel resource was temporarily unavailable. > */ > -int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior) > +int do_madvise(struct mm_struct *mm, unsigned long start, unsigned long len_in, > + int behavior, unsigned int flags) > { > unsigned long end, tmp; > struct vm_area_struct *vma, *prev; > int unmapped_error = 0; > int error = -EINVAL; > + int error_on_gap; > int write; > - size_t len; > + unsigned long len; > struct blk_plug plug; > + bool range_madvise = !!(flags & PMADV_FLAG_RANGE); > + > + /* For range operations gap between VMAs is normal */ > + error_on_gap = range_madvise ? 0 : -ENOMEM; > > start = untagged_addr(start); > > @@ -1123,13 +1137,14 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh > blk_start_plug(&plug); > for (;;) { > /* Still start < end. */ > - error = -ENOMEM; > + error = error_on_gap; > + > if (!vma) > goto out; > > /* Here start < (end|vma->vm_end). */ > if (start < vma->vm_start) { > - unmapped_error = -ENOMEM; > + unmapped_error = error_on_gap; > start = vma->vm_start; > if (start >= end) > goto out; > @@ -1140,10 +1155,18 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh > if (end < tmp) > tmp = end; > > + /* For range operations skip VMAs ineligible for the behavior */ > + if (range_madvise && !can_range_madv_lru_vma(vma, behavior)) { > + prev = vma; > + goto skip_vma; > + } > + > /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ > error = madvise_vma(vma, &prev, start, tmp, behavior); > if (error) > goto out; > + > +skip_vma: > start = tmp; > if (prev && start < prev->vm_end) > start = prev->vm_end; > @@ -1167,7 +1190,7 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh > > SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) > { > - return do_madvise(current->mm, start, len_in, behavior); > + return do_madvise(current->mm, start, len_in, behavior, 0); > } > > SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, > @@ -1183,7 +1206,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, > size_t total_len; > unsigned int f_flags; > > - if (flags != 0) { > + if (flags & ~PMADV_FLAG_MASK) { > ret = -EINVAL; > goto out; > } > @@ -1216,12 +1239,21 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, > goto release_task; > } > > + /* > + * For range madvise only the entire address space is supported for now > + * and input iovec is ignored. > + */ > + if (flags & PMADV_FLAG_RANGE) { > + ret = do_madvise(mm, 0, ULONG_MAX & PAGE_MASK, behavior, flags); > + goto release_mm; > + } > + > total_len = iov_iter_count(&iter); > > while (iov_iter_count(&iter)) { > iovec = iov_iter_iovec(&iter); > ret = do_madvise(mm, (unsigned long)iovec.iov_base, > - iovec.iov_len, behavior); > + iovec.iov_len, behavior, flags); > if (ret < 0) > break; > iov_iter_advance(&iter, iovec.iov_len); > @@ -1230,6 +1262,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, > if (ret == 0) > ret = total_len - iov_iter_count(&iter); > > +release_mm: > mmput(mm); > release_task: > put_task_struct(task); > diff --git a/tools/include/uapi/asm-generic/mman-common.h b/tools/include/uapi/asm-generic/mman-common.h > index f94f65d429be..4898034593ec 100644 > --- a/tools/include/uapi/asm-generic/mman-common.h > +++ b/tools/include/uapi/asm-generic/mman-common.h > @@ -80,4 +80,8 @@ > #define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\ > PKEY_DISABLE_WRITE) > > +/* process_madvise flags */ > +#define PMADV_FLAG_RANGE 0x1 /* advice for all VMAs in the range */ > +#define PMADV_FLAG_MASK (PMADV_FLAG_RANGE) > + > #endif /* __ASM_GENERIC_MMAN_COMMON_H */ > -- > 2.29.2.454.gaff20da3a2-goog >