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From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Cc: "Oleg Nesterov" <oleg@redhat.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Michal Hocko" <mhocko@kernel.org>,
	"Cyrill Gorcunov" <gorcunov@gmail.com>,
	"Kirill Tkhai" <ktkhai@virtuozzo.com>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Roman Gushchin" <guro@fb.com>
Subject: [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files
Date: Sun, 09 Jun 2019 13:09:00 +0300
Message-ID: <156007493995.3335.9595044802115356911.stgit@buzz> (raw)
In-Reply-To: <156007465229.3335.10259979070641486905.stgit@buzz>

Do not stuck forever if something wrong.
Killable lock allows to cleanup stuck tasks and simplifies investigation.

It seems ->d_revalidate() could return any error (except ECHILD) to
abort validation and pass error as result of lookup sequence.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 fs/proc/base.c |   27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9c8ca6cd3ce4..515ab29c2adf 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1962,9 +1962,12 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
 		goto out;
 
 	if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
-		down_read(&mm->mmap_sem);
-		exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end);
-		up_read(&mm->mmap_sem);
+		status = down_read_killable(&mm->mmap_sem);
+		if (!status) {
+			exact_vma_exists = !!find_exact_vma(mm, vm_start,
+							    vm_end);
+			up_read(&mm->mmap_sem);
+		}
 	}
 
 	mmput(mm);
@@ -2010,8 +2013,11 @@ static int map_files_get_link(struct dentry *dentry, struct path *path)
 	if (rc)
 		goto out_mmput;
 
+	rc = down_read_killable(&mm->mmap_sem);
+	if (rc)
+		goto out_mmput;
+
 	rc = -ENOENT;
-	down_read(&mm->mmap_sem);
 	vma = find_exact_vma(mm, vm_start, vm_end);
 	if (vma && vma->vm_file) {
 		*path = vma->vm_file->f_path;
@@ -2107,7 +2113,10 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
 	if (!mm)
 		goto out_put_task;
 
-	down_read(&mm->mmap_sem);
+	result = ERR_PTR(-EINTR);
+	if (down_read_killable(&mm->mmap_sem))
+		goto out_put_mm;
+
 	vma = find_exact_vma(mm, vm_start, vm_end);
 	if (!vma)
 		goto out_no_vma;
@@ -2118,6 +2127,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
 
 out_no_vma:
 	up_read(&mm->mmap_sem);
+out_put_mm:
 	mmput(mm);
 out_put_task:
 	put_task_struct(task);
@@ -2160,7 +2170,12 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 	mm = get_task_mm(task);
 	if (!mm)
 		goto out_put_task;
-	down_read(&mm->mmap_sem);
+
+	ret = down_read_killable(&mm->mmap_sem);
+	if (ret) {
+		mmput(mm);
+		goto out_put_task;
+	}
 
 	nr_files = 0;
 


  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-09 10:08 [PATCH v2 0/6] mm: use down_read_killable for locking mmap_sem in proc Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 1/6] proc: use down_read_killable mmap_sem for /proc/pid/maps Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 2/6] proc: use down_read_killable mmap_sem for /proc/pid/smaps_rollup Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 3/6] proc: use down_read_killable mmap_sem for /proc/pid/pagemap Konstantin Khlebnikov
2019-06-09 10:08 ` [PATCH v2 4/6] proc: use down_read_killable mmap_sem for /proc/pid/clear_refs Konstantin Khlebnikov
2019-06-09 10:09 ` Konstantin Khlebnikov [this message]
2019-06-12 23:14   ` [PATCH v2 5/6] proc: use down_read_killable mmap_sem for /proc/pid/map_files Andrei Vagin
2019-06-13  0:04     ` Andrew Morton
2019-06-13  6:48     ` Cyrill Gorcunov
2019-06-13  8:15     ` Konstantin Khlebnikov
2019-06-13 20:32       ` Andrei Vagin
2019-06-09 10:09 ` [PATCH v2 6/6] mm: use down_read_killable for locking mmap_sem in access_remote_vm Konstantin Khlebnikov

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