From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
cluster-devel@redhat.com, linux-kernel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
Matthew Wilcox <willy@infradead.org>
Subject: [RFC 4/9] gfs2: Fix mmap + page fault deadlocks (part 1)
Date: Mon, 31 May 2021 19:01:18 +0200 [thread overview]
Message-ID: <20210531170123.243771-5-agruenba@redhat.com> (raw)
In-Reply-To: <20210531170123.243771-1-agruenba@redhat.com>
When the buffer passed to a read or write system call is memory mapped
to the same file, a page fault can occur in filemap_fault. In that
case, the task will already be holding the inode glock, and trying to
take the same lock again will result in a BUG in add_to_queue().
Fix that by recognizing the self-recursion case. Either skip the lock
taking (when the glock is held in a compatible way), or fail the
operation.
Likewise, a request to un-share a copy-on-write page can *probably*
happen in similar situations, so treat the locking in gfs2_page_mkwrite
in the same way.
A future patch will handle these case more gracefully by retrying
operations instead of failing them, along with addressing more complex
deadlock scenarios.
Reported-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/gfs2/file.c | 40 ++++++++++++++++++++++++++++++----------
1 file changed, 30 insertions(+), 10 deletions(-)
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 6d77743f11a4..7d88abb4629b 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -423,6 +423,7 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
struct page *page = vmf->page;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_holder *outer_gh = gfs2_glock_is_locked_by_me(ip->i_gl);
struct gfs2_sbd *sdp = GFS2_SB(inode);
struct gfs2_alloc_parms ap = { .aflags = 0, };
u64 offset = page_offset(page);
@@ -436,10 +437,18 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
sb_start_pagefault(inode->i_sb);
gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
- err = gfs2_glock_nq(&gh);
- if (err) {
- ret = block_page_mkwrite_return(err);
- goto out_uninit;
+ if (likely(!outer_gh)) {
+ err = gfs2_glock_nq(&gh);
+ if (err) {
+ ret = block_page_mkwrite_return(err);
+ goto out_uninit;
+ }
+ } else {
+ if (!gfs2_holder_is_compatible(outer_gh, LM_ST_EXCLUSIVE)) {
+ /* We could try to upgrade outer_gh here. */
+ ret = VM_FAULT_SIGBUS;
+ goto out_uninit;
+ }
}
/* Check page index against inode size */
@@ -540,7 +549,8 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
out_quota_unlock:
gfs2_quota_unlock(ip);
out_unlock:
- gfs2_glock_dq(&gh);
+ if (likely(!outer_gh))
+ gfs2_glock_dq(&gh);
out_uninit:
gfs2_holder_uninit(&gh);
if (ret == VM_FAULT_LOCKED) {
@@ -555,6 +565,7 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_holder *outer_gh = gfs2_glock_is_locked_by_me(ip->i_gl);
struct gfs2_holder gh;
vm_fault_t ret;
u16 state;
@@ -562,13 +573,22 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
state = (vmf->flags & FAULT_FLAG_WRITE) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
gfs2_holder_init(ip->i_gl, state, 0, &gh);
- err = gfs2_glock_nq(&gh);
- if (err) {
- ret = block_page_mkwrite_return(err);
- goto out_uninit;
+ if (likely(!outer_gh)) {
+ err = gfs2_glock_nq(&gh);
+ if (err) {
+ ret = block_page_mkwrite_return(err);
+ goto out_uninit;
+ }
+ } else {
+ if (!gfs2_holder_is_compatible(outer_gh, state)) {
+ /* We could try to upgrade outer_gh here. */
+ ret = VM_FAULT_SIGBUS;
+ goto out_uninit;
+ }
}
ret = filemap_fault(vmf);
- gfs2_glock_dq(&gh);
+ if (likely(!outer_gh))
+ gfs2_glock_dq(&gh);
out_uninit:
gfs2_holder_uninit(&gh);
return ret;
--
2.26.3
WARNING: multiple messages have this Message-ID (diff)
From: Andreas Gruenbacher <agruenba@redhat.com>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [RFC 4/9] gfs2: Fix mmap + page fault deadlocks (part 1)
Date: Mon, 31 May 2021 19:01:18 +0200 [thread overview]
Message-ID: <20210531170123.243771-5-agruenba@redhat.com> (raw)
In-Reply-To: <20210531170123.243771-1-agruenba@redhat.com>
When the buffer passed to a read or write system call is memory mapped
to the same file, a page fault can occur in filemap_fault. In that
case, the task will already be holding the inode glock, and trying to
take the same lock again will result in a BUG in add_to_queue().
Fix that by recognizing the self-recursion case. Either skip the lock
taking (when the glock is held in a compatible way), or fail the
operation.
Likewise, a request to un-share a copy-on-write page can *probably*
happen in similar situations, so treat the locking in gfs2_page_mkwrite
in the same way.
A future patch will handle these case more gracefully by retrying
operations instead of failing them, along with addressing more complex
deadlock scenarios.
Reported-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/gfs2/file.c | 40 ++++++++++++++++++++++++++++++----------
1 file changed, 30 insertions(+), 10 deletions(-)
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 6d77743f11a4..7d88abb4629b 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -423,6 +423,7 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
struct page *page = vmf->page;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_holder *outer_gh = gfs2_glock_is_locked_by_me(ip->i_gl);
struct gfs2_sbd *sdp = GFS2_SB(inode);
struct gfs2_alloc_parms ap = { .aflags = 0, };
u64 offset = page_offset(page);
@@ -436,10 +437,18 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
sb_start_pagefault(inode->i_sb);
gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
- err = gfs2_glock_nq(&gh);
- if (err) {
- ret = block_page_mkwrite_return(err);
- goto out_uninit;
+ if (likely(!outer_gh)) {
+ err = gfs2_glock_nq(&gh);
+ if (err) {
+ ret = block_page_mkwrite_return(err);
+ goto out_uninit;
+ }
+ } else {
+ if (!gfs2_holder_is_compatible(outer_gh, LM_ST_EXCLUSIVE)) {
+ /* We could try to upgrade outer_gh here. */
+ ret = VM_FAULT_SIGBUS;
+ goto out_uninit;
+ }
}
/* Check page index against inode size */
@@ -540,7 +549,8 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
out_quota_unlock:
gfs2_quota_unlock(ip);
out_unlock:
- gfs2_glock_dq(&gh);
+ if (likely(!outer_gh))
+ gfs2_glock_dq(&gh);
out_uninit:
gfs2_holder_uninit(&gh);
if (ret == VM_FAULT_LOCKED) {
@@ -555,6 +565,7 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_holder *outer_gh = gfs2_glock_is_locked_by_me(ip->i_gl);
struct gfs2_holder gh;
vm_fault_t ret;
u16 state;
@@ -562,13 +573,22 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
state = (vmf->flags & FAULT_FLAG_WRITE) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
gfs2_holder_init(ip->i_gl, state, 0, &gh);
- err = gfs2_glock_nq(&gh);
- if (err) {
- ret = block_page_mkwrite_return(err);
- goto out_uninit;
+ if (likely(!outer_gh)) {
+ err = gfs2_glock_nq(&gh);
+ if (err) {
+ ret = block_page_mkwrite_return(err);
+ goto out_uninit;
+ }
+ } else {
+ if (!gfs2_holder_is_compatible(outer_gh, state)) {
+ /* We could try to upgrade outer_gh here. */
+ ret = VM_FAULT_SIGBUS;
+ goto out_uninit;
+ }
}
ret = filemap_fault(vmf);
- gfs2_glock_dq(&gh);
+ if (likely(!outer_gh))
+ gfs2_glock_dq(&gh);
out_uninit:
gfs2_holder_uninit(&gh);
return ret;
--
2.26.3
next prev parent reply other threads:[~2021-05-31 17:09 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-31 17:01 [RFC 0/9] gfs2: handle page faults during read and write Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 1/9] gfs2: Clean up the error handling in gfs2_page_mkwrite Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 2/9] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 3/9] gfs2: Add gfs2_holder_is_compatible helper Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` Andreas Gruenbacher [this message]
2021-05-31 17:01 ` [Cluster-devel] [RFC 4/9] gfs2: Fix mmap + page fault deadlocks (part 1) Andreas Gruenbacher
2021-06-01 6:00 ` Linus Torvalds
2021-06-01 6:00 ` [Cluster-devel] " Linus Torvalds
2021-06-02 11:16 ` Andreas Gruenbacher
2021-06-02 11:16 ` [Cluster-devel] " Andreas Gruenbacher
2021-06-11 16:25 ` Al Viro
2021-06-11 16:25 ` [Cluster-devel] " Al Viro
2021-06-12 21:05 ` Al Viro
2021-06-12 21:05 ` [Cluster-devel] " Al Viro
2021-06-12 21:35 ` Al Viro
2021-06-12 21:35 ` [Cluster-devel] " Al Viro
2021-06-13 8:44 ` Steven Whitehouse
2021-06-13 8:44 ` Steven Whitehouse
2021-05-31 17:01 ` [RFC 5/9] iov_iter: Add iov_iter_fault_in_writeable() Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:12 ` Al Viro
2021-05-31 17:12 ` [Cluster-devel] " Al Viro
2021-06-12 21:12 ` Al Viro
2021-06-12 21:12 ` [Cluster-devel] " Al Viro
2021-06-12 21:33 ` Linus Torvalds
2021-06-12 21:33 ` [Cluster-devel] " Linus Torvalds
2021-06-12 21:47 ` Al Viro
2021-06-12 21:47 ` [Cluster-devel] " Al Viro
2021-06-12 23:17 ` Linus Torvalds
2021-06-12 23:17 ` [Cluster-devel] " Linus Torvalds
2021-06-12 23:38 ` Al Viro
2021-06-12 23:38 ` [Cluster-devel] " Al Viro
2021-05-31 17:01 ` [RFC 6/9] gfs2: Add wrappers for accessing journal_info Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 7/9] gfs2: Encode glock holding and retry flags in journal_info Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 8/9] gfs2: Add LM_FLAG_OUTER glock holder flag Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-05-31 17:01 ` [RFC 9/9] gfs2: Fix mmap + page fault deadlocks (part 2) Andreas Gruenbacher
2021-05-31 17:01 ` [Cluster-devel] " Andreas Gruenbacher
2021-06-01 5:47 ` Linus Torvalds
2021-06-01 5:47 ` [Cluster-devel] " Linus Torvalds
2021-05-31 17:57 ` [Cluster-devel] [RFC 0/9] gfs2: handle page faults during read and write Linus Torvalds
2021-05-31 20:35 ` Andreas Gruenbacher
2021-05-31 20:35 ` [Cluster-devel] " Andreas Gruenbacher
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