From: Johannes Weiner <hannes@cmpxchg.org>
To: Song Liu <songliubraving@fb.com>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, matthew.wilcox@oracle.com,
kirill.shutemov@linux.intel.com, kernel-team@fb.com,
william.kucharski@oracle.com, akpm@linux-foundation.org,
hdanton@sina.com
Subject: Re: [PATCH v9 6/6] mm,thp: avoid writes to file with THP in pagecache
Date: Wed, 10 Jul 2019 15:11:16 -0400 [thread overview]
Message-ID: <20190710191116.GG11197@cmpxchg.org> (raw)
In-Reply-To: <20190625001246.685563-7-songliubraving@fb.com>
On Mon, Jun 24, 2019 at 05:12:46PM -0700, Song Liu wrote:
> In previous patch, an application could put part of its text section in
> THP via madvise(). These THPs will be protected from writes when the
> application is still running (TXTBSY). However, after the application
> exits, the file is available for writes.
>
> This patch avoids writes to file THP by dropping page cache for the file
> when the file is open for write. A new counter nr_thps is added to struct
> address_space. In do_last(), if the file is open for write and nr_thps
> is non-zero, we drop page cache for the whole file.
>
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Song Liu <songliubraving@fb.com>
> ---
> fs/inode.c | 3 +++
> fs/namei.c | 23 ++++++++++++++++++++++-
> include/linux/fs.h | 32 ++++++++++++++++++++++++++++++++
> mm/filemap.c | 1 +
> mm/khugepaged.c | 4 +++-
> 5 files changed, 61 insertions(+), 2 deletions(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index df6542ec3b88..518113a4e219 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -181,6 +181,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
> mapping->flags = 0;
> mapping->wb_err = 0;
> atomic_set(&mapping->i_mmap_writable, 0);
> +#ifdef CONFIG_READ_ONLY_THP_FOR_FS
> + atomic_set(&mapping->nr_thps, 0);
> +#endif
> mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
> mapping->private_data = NULL;
> mapping->writeback_index = 0;
> diff --git a/fs/namei.c b/fs/namei.c
> index 20831c2fbb34..3d95e94029cc 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3249,6 +3249,23 @@ static int lookup_open(struct nameidata *nd, struct path *path,
> return error;
> }
>
> +/*
> + * The file is open for write, so it is not mmapped with VM_DENYWRITE. If
> + * it still has THP in page cache, drop the whole file from pagecache
> + * before processing writes. This helps us avoid handling write back of
> + * THP for now.
> + */
> +static inline void release_file_thp(struct file *file)
> +{
> + if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) {
> + struct inode *inode = file_inode(file);
> +
> + if (inode_is_open_for_write(inode) &&
> + filemap_nr_thps(inode->i_mapping))
> + truncate_pagecache(inode, 0);
> + }
> +}
> +
> /*
> * Handle the last step of open()
> */
> @@ -3418,7 +3435,11 @@ static int do_last(struct nameidata *nd,
> goto out;
> opened:
> error = ima_file_check(file, op->acc_mode);
> - if (!error && will_truncate)
> + if (error)
> + goto out;
> +
> + release_file_thp(file);
> + if (will_truncate)
> error = handle_truncate(file);
This would seem better placed in do_dentry_open(), where we're done
with the namespace operation and actually work against the inode.
Something roughly like this?
diff --git a/fs/open.c b/fs/open.c
index b5b80469b93d..cae893edbab6 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -799,6 +799,11 @@ static int do_dentry_open(struct file *f,
if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
return -EINVAL;
}
+
+ /* XXX: Huge page cache doesn't support writing yet */
+ if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))
+ truncate_pagecache(inode, 0);
+
return 0;
cleanup_all:
next prev parent reply other threads:[~2019-07-10 19:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 0:12 [PATCH v9 0/6] Enable THP for text section of non-shmem files Song Liu
2019-06-25 0:12 ` [PATCH v9 1/6] filemap: check compound_head(page)->mapping in filemap_fault() Song Liu
2019-07-10 17:44 ` Johannes Weiner
2019-07-10 17:51 ` Johannes Weiner
2019-06-25 0:12 ` [PATCH v9 2/6] filemap: update offset check " Song Liu
2019-07-10 17:52 ` Johannes Weiner
2019-06-25 0:12 ` [PATCH v9 3/6] mm,thp: stats for file backed THP Song Liu
2019-07-10 17:59 ` Johannes Weiner
2019-06-25 0:12 ` [PATCH v9 4/6] khugepaged: rename collapse_shmem() and khugepaged_scan_shmem() Song Liu
2019-06-27 13:19 ` Rik van Riel
2019-07-10 18:21 ` Johannes Weiner
2019-06-25 0:12 ` [PATCH v9 5/6] mm,thp: add read-only THP support for (non-shmem) FS Song Liu
2019-07-10 18:48 ` Johannes Weiner
2019-07-22 23:41 ` Song Liu
2019-07-23 23:59 ` Huang, Kai
2019-07-28 6:41 ` Song Liu
2019-06-25 0:12 ` [PATCH v9 6/6] mm,thp: avoid writes to file with THP in pagecache Song Liu
2019-06-27 13:18 ` Rik van Riel
2019-07-10 19:11 ` Johannes Weiner [this message]
2019-06-27 12:46 ` [PATCH v9 0/6] Enable THP for text section of non-shmem files Kirill A. Shutemov
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