* [PATCH] afs: Re-enable freezing once a page fault is interrupted
@ 2021-06-16 21:22 David Howells
2021-06-18 20:52 ` Linus Torvalds
0 siblings, 1 reply; 3+ messages in thread
From: David Howells @ 2021-06-16 21:22 UTC (permalink / raw)
To: torvalds
Cc: Matthew Wilcox (Oracle),
linux-afs, dhowells, marc.dionne, linux-afs, linux-fsdevel,
linux-kernel
From: Matthew Wilcox (Oracle) <willy@infradead.org>
If a task is killed during a page fault, it does not currently call
sb_end_pagefault(), which means that the filesystem cannot be frozen
at any time thereafter. This may be reported by lockdep like this:
====================================
WARNING: fsstress/10757 still has locks held!
5.13.0-rc4-build4+ #91 Not tainted
------------------------------------
1 lock held by fsstress/10757:
#0: ffff888104eac530
(
sb_pagefaults
as filesystem freezing is modelled as a lock.
Fix this by removing all the direct returns from within the function,
and using 'ret' to indicate whether we were interrupted or successful.
Fixes: 1cf7a1518aef ("afs: Implement shared-writeable mmap")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20210616154900.1958373-1-willy@infradead.org/
---
fs/afs/write.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index f722cb80a594..ff36800a7389 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -848,6 +848,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
struct inode *inode = file_inode(file);
struct afs_vnode *vnode = AFS_FS_I(inode);
unsigned long priv;
+ vm_fault_t ret = VM_FAULT_RETRY;
_enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, page->index);
@@ -859,14 +860,14 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page) &&
wait_on_page_fscache_killable(page) < 0)
- return VM_FAULT_RETRY;
+ goto out;
#endif
if (wait_on_page_writeback_killable(page))
- return VM_FAULT_RETRY;
+ goto out;
if (lock_page_killable(page) < 0)
- return VM_FAULT_RETRY;
+ goto out;
/* We mustn't change page->private until writeback is complete as that
* details the portion of the page we need to write back and we might
@@ -874,7 +875,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
*/
if (wait_on_page_writeback_killable(page) < 0) {
unlock_page(page);
- return VM_FAULT_RETRY;
+ goto out;
}
priv = afs_page_dirty(page, 0, thp_size(page));
@@ -888,8 +889,10 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
}
file_update_time(file);
+ ret = VM_FAULT_LOCKED;
+out:
sb_end_pagefault(inode->i_sb);
- return VM_FAULT_LOCKED;
+ return ret;
}
/*
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] afs: Re-enable freezing once a page fault is interrupted
2021-06-16 21:22 [PATCH] afs: Re-enable freezing once a page fault is interrupted David Howells
@ 2021-06-18 20:52 ` Linus Torvalds
0 siblings, 0 replies; 3+ messages in thread
From: Linus Torvalds @ 2021-06-18 20:52 UTC (permalink / raw)
To: David Howells
Cc: Matthew Wilcox (Oracle),
linux-afs, Marc Dionne, linux-fsdevel, Linux Kernel Mailing List
On Wed, Jun 16, 2021 at 2:22 PM David Howells <dhowells@redhat.com> wrote:
>
> If a task is killed during a page fault, it does not currently call
> sb_end_pagefault(), which means that the filesystem cannot be frozen
> at any time thereafter. This may be reported by lockdep like this:
I've applied this patch.
Everything in my screams "the sb_start/end_pagefault() code is
completely broken", but in the meantime this patch fixes the immediate
bug.
I suspect that the whole sb_start/end_pagefault thing should just go
away entirely, and the freezer should be re-examined. Alternatively,
it should just be done by generic code, not by the filesystem.
But it is what it is.
Linus
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] afs: Re-enable freezing once a page fault is interrupted
@ 2021-06-16 15:49 Matthew Wilcox (Oracle)
0 siblings, 0 replies; 3+ messages in thread
From: Matthew Wilcox (Oracle) @ 2021-06-16 15:49 UTC (permalink / raw)
To: David Howells, Marc Dionne, linux-afs, linux-kernel, linux-fsdevel
Cc: Matthew Wilcox (Oracle)
If a task is killed during a page fault, it does not currently call
sb_end_pagefault(), which means that the filesystem cannot be frozen
at any time thereafter. This may be reported by lockdep like this:
====================================
WARNING: fsstress/10757 still has locks held!
5.13.0-rc4-build4+ #91 Not tainted
------------------------------------
1 lock held by fsstress/10757:
#0: ffff888104eac530
(
sb_pagefaults
as filesystem freezing is modelled as a lock.
Fix this by removing all the direct returns from within the function,
and using 'ret' to indicate whether we were interrupted or successful.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/afs/write.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index a523bb86915d..62dd906f9b72 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -832,6 +832,7 @@ int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
*/
vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
{
+ vm_fault_t ret = VM_FAULT_RETRY;
struct page *page = thp_head(vmf->page);
struct file *file = vmf->vma->vm_file;
struct inode *inode = file_inode(file);
@@ -848,14 +849,14 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page) &&
wait_on_page_fscache_killable(page) < 0)
- return VM_FAULT_RETRY;
+ goto out;
#endif
if (wait_on_page_writeback_killable(page))
- return VM_FAULT_RETRY;
+ goto out;
if (lock_page_killable(page) < 0)
- return VM_FAULT_RETRY;
+ goto out;
/* We mustn't change page->private until writeback is complete as that
* details the portion of the page we need to write back and we might
@@ -863,7 +864,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
*/
if (wait_on_page_writeback_killable(page) < 0) {
unlock_page(page);
- return VM_FAULT_RETRY;
+ goto out;
}
priv = afs_page_dirty(page, 0, thp_size(page));
@@ -877,8 +878,10 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
}
file_update_time(file);
+ ret = VM_FAULT_LOCKED;
+out:
sb_end_pagefault(inode->i_sb);
- return VM_FAULT_LOCKED;
+ return ret;
}
/*
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
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