* [PATCH] fuse: avoid scheduling while atomic
@ 2014-06-25 12:17 Maxim Patlasov
2014-07-04 16:27 ` Miklos Szeredi
0 siblings, 1 reply; 3+ messages in thread
From: Maxim Patlasov @ 2014-06-25 12:17 UTC (permalink / raw)
To: miklos; +Cc: fuse-devel, linux-kernel
As reported by Richard Sharpe, an attempt to use fuse_notify_inval_entry()
triggers complains about scheduling while atomic:
> Jun 23 11:53:24 localhost kernel: BUG: scheduling while atomic:
fuse.hf/13976/0x10000001
This happens because fuse_notify_inval_entry() attempts to allocate memory
with GFP_KERNEL, holding "struct fuse_copy_state" mapped by kmap_atomic().
The patch fixes the problem for fuse_notify_inval_entry() and other notifiers
by unmapping fuse_copy_state before allocations and remapping it again
afterwards.
Reported-by: Richard Sharpe <realrichardsharpe@gmail.com>
Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
---
fs/fuse/dev.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 098f97b..502aa1d 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -755,6 +755,22 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
return lock_request(cs->fc, cs->req);
}
+static void fuse_copy_unmap(struct fuse_copy_state *cs)
+{
+ cs->buf = (void *)(cs->buf - cs->mapaddr);
+ kunmap_atomic(cs->mapaddr);
+}
+
+static void fuse_copy_remap(struct fuse_copy_state *cs)
+{
+ if (cs->currbuf)
+ cs->mapaddr = kmap_atomic(cs->currbuf->page);
+ else
+ cs->mapaddr = kmap_atomic(cs->pg);
+
+ cs->buf = (unsigned long)cs->buf + cs->mapaddr;
+}
+
/* Do as much copy to/from userspace buffer as we can */
static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
{
@@ -1431,7 +1447,9 @@ static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
char *buf;
struct qstr name;
+ fuse_copy_unmap(cs);
buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+ fuse_copy_remap(cs);
if (!buf)
goto err;
@@ -1482,7 +1500,9 @@ static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
char *buf;
struct qstr name;
+ fuse_copy_unmap(cs);
buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+ fuse_copy_remap(cs);
if (!buf)
goto err;
@@ -1554,6 +1574,7 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
nodeid = outarg.nodeid;
+ fuse_copy_unmap(cs);
down_read(&fc->killsb);
err = -ENOENT;
@@ -1586,7 +1607,9 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
goto out_iput;
this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
+ fuse_copy_remap(cs);
err = fuse_copy_page(cs, &page, offset, this_num, 0);
+ fuse_copy_unmap(cs);
if (!err && offset == 0 &&
(this_num == PAGE_CACHE_SIZE || file_size == end))
SetPageUptodate(page);
@@ -1607,6 +1630,7 @@ out_iput:
iput(inode);
out_up_killsb:
up_read(&fc->killsb);
+ fuse_copy_remap(cs);
out_finish:
fuse_copy_finish(cs);
return err;
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] fuse: avoid scheduling while atomic
2014-06-25 12:17 [PATCH] fuse: avoid scheduling while atomic Maxim Patlasov
@ 2014-07-04 16:27 ` Miklos Szeredi
2014-07-14 15:53 ` Maxim Patlasov
0 siblings, 1 reply; 3+ messages in thread
From: Miklos Szeredi @ 2014-07-04 16:27 UTC (permalink / raw)
To: Maxim Patlasov; +Cc: fuse-devel, linux-kernel, Richard Sharpe
Maxim, thanks for the patch.
Here's a reworked one. While it looks a bit more complicated, its chances of
being (and remaining) correct are, I think, better, since the region surrounded
by kmap/kunmap_atomic is trivially non-sleeping. This patch also removes more
lines than it adds, as an added bonus.
Please review and test if possible.
Thanks,
Miklos
---
fs/fuse/dev.c | 51 +++++++++++++++++++++++----------------------------
1 file changed, 23 insertions(+), 28 deletions(-)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -643,9 +643,8 @@ struct fuse_copy_state {
unsigned long seglen;
unsigned long addr;
struct page *pg;
- void *mapaddr;
- void *buf;
unsigned len;
+ unsigned offset;
unsigned move_pages:1;
};
@@ -666,23 +665,17 @@ static void fuse_copy_finish(struct fuse
if (cs->currbuf) {
struct pipe_buffer *buf = cs->currbuf;
- if (!cs->write) {
- kunmap_atomic(cs->mapaddr);
- } else {
- kunmap_atomic(cs->mapaddr);
+ if (cs->write)
buf->len = PAGE_SIZE - cs->len;
- }
cs->currbuf = NULL;
- cs->mapaddr = NULL;
- } else if (cs->mapaddr) {
- kunmap_atomic(cs->mapaddr);
+ } else if (cs->pg) {
if (cs->write) {
flush_dcache_page(cs->pg);
set_page_dirty_lock(cs->pg);
}
put_page(cs->pg);
- cs->mapaddr = NULL;
}
+ cs->pg = NULL;
}
/*
@@ -691,7 +684,7 @@ static void fuse_copy_finish(struct fuse
*/
static int fuse_copy_fill(struct fuse_copy_state *cs)
{
- unsigned long offset;
+ struct page *page;
int err;
unlock_request(cs->fc, cs->req);
@@ -706,14 +699,12 @@ static int fuse_copy_fill(struct fuse_co
BUG_ON(!cs->nr_segs);
cs->currbuf = buf;
- cs->mapaddr = kmap_atomic(buf->page);
+ cs->pg = buf->page;
+ cs->offset = buf->offset;
cs->len = buf->len;
- cs->buf = cs->mapaddr + buf->offset;
cs->pipebufs++;
cs->nr_segs--;
} else {
- struct page *page;
-
if (cs->nr_segs == cs->pipe->buffers)
return -EIO;
@@ -726,8 +717,8 @@ static int fuse_copy_fill(struct fuse_co
buf->len = 0;
cs->currbuf = buf;
- cs->mapaddr = kmap_atomic(page);
- cs->buf = cs->mapaddr;
+ cs->pg = page;
+ cs->offset = 0;
cs->len = PAGE_SIZE;
cs->pipebufs++;
cs->nr_segs++;
@@ -740,14 +731,13 @@ static int fuse_copy_fill(struct fuse_co
cs->iov++;
cs->nr_segs--;
}
- err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
+ err = get_user_pages_fast(cs->addr, 1, cs->write, &page);
if (err < 0)
return err;
BUG_ON(err != 1);
- offset = cs->addr % PAGE_SIZE;
- cs->mapaddr = kmap_atomic(cs->pg);
- cs->buf = cs->mapaddr + offset;
- cs->len = min(PAGE_SIZE - offset, cs->seglen);
+ cs->pg = page;
+ cs->offset = cs->addr % PAGE_SIZE;
+ cs->len = min(PAGE_SIZE - cs->offset, cs->seglen);
cs->seglen -= cs->len;
cs->addr += cs->len;
}
@@ -760,15 +750,20 @@ static int fuse_copy_do(struct fuse_copy
{
unsigned ncpy = min(*size, cs->len);
if (val) {
+ void *pgaddr = kmap_atomic(cs->pg);
+ void *buf = pgaddr + cs->offset;
+
if (cs->write)
- memcpy(cs->buf, *val, ncpy);
+ memcpy(buf, *val, ncpy);
else
- memcpy(*val, cs->buf, ncpy);
+ memcpy(*val, buf, ncpy);
+
+ kunmap_atomic(pgaddr);
*val += ncpy;
}
*size -= ncpy;
cs->len -= ncpy;
- cs->buf += ncpy;
+ cs->offset += ncpy;
return ncpy;
}
@@ -874,8 +869,8 @@ static int fuse_try_move_page(struct fus
out_fallback_unlock:
unlock_page(newpage);
out_fallback:
- cs->mapaddr = kmap_atomic(buf->page);
- cs->buf = cs->mapaddr + buf->offset;
+ cs->pg = buf->page;
+ cs->offset = buf->offset;
err = lock_request(cs->fc, cs->req);
if (err)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] fuse: avoid scheduling while atomic
2014-07-04 16:27 ` Miklos Szeredi
@ 2014-07-14 15:53 ` Maxim Patlasov
0 siblings, 0 replies; 3+ messages in thread
From: Maxim Patlasov @ 2014-07-14 15:53 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: fuse-devel, linux-kernel, Richard Sharpe
On 07/04/2014 08:27 PM, Miklos Szeredi wrote:
> Maxim, thanks for the patch.
>
> Here's a reworked one. While it looks a bit more complicated, its chances of
> being (and remaining) correct are, I think, better, since the region surrounded
> by kmap/kunmap_atomic is trivially non-sleeping. This patch also removes more
> lines than it adds, as an added bonus.
>
> Please review and test if possible.
The patch looks fine and works well in my tests.
Maxim
>
> Thanks,
> Miklos
>
> ---
> fs/fuse/dev.c | 51 +++++++++++++++++++++++----------------------------
> 1 file changed, 23 insertions(+), 28 deletions(-)
>
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -643,9 +643,8 @@ struct fuse_copy_state {
> unsigned long seglen;
> unsigned long addr;
> struct page *pg;
> - void *mapaddr;
> - void *buf;
> unsigned len;
> + unsigned offset;
> unsigned move_pages:1;
> };
>
> @@ -666,23 +665,17 @@ static void fuse_copy_finish(struct fuse
> if (cs->currbuf) {
> struct pipe_buffer *buf = cs->currbuf;
>
> - if (!cs->write) {
> - kunmap_atomic(cs->mapaddr);
> - } else {
> - kunmap_atomic(cs->mapaddr);
> + if (cs->write)
> buf->len = PAGE_SIZE - cs->len;
> - }
> cs->currbuf = NULL;
> - cs->mapaddr = NULL;
> - } else if (cs->mapaddr) {
> - kunmap_atomic(cs->mapaddr);
> + } else if (cs->pg) {
> if (cs->write) {
> flush_dcache_page(cs->pg);
> set_page_dirty_lock(cs->pg);
> }
> put_page(cs->pg);
> - cs->mapaddr = NULL;
> }
> + cs->pg = NULL;
> }
>
> /*
> @@ -691,7 +684,7 @@ static void fuse_copy_finish(struct fuse
> */
> static int fuse_copy_fill(struct fuse_copy_state *cs)
> {
> - unsigned long offset;
> + struct page *page;
> int err;
>
> unlock_request(cs->fc, cs->req);
> @@ -706,14 +699,12 @@ static int fuse_copy_fill(struct fuse_co
>
> BUG_ON(!cs->nr_segs);
> cs->currbuf = buf;
> - cs->mapaddr = kmap_atomic(buf->page);
> + cs->pg = buf->page;
> + cs->offset = buf->offset;
> cs->len = buf->len;
> - cs->buf = cs->mapaddr + buf->offset;
> cs->pipebufs++;
> cs->nr_segs--;
> } else {
> - struct page *page;
> -
> if (cs->nr_segs == cs->pipe->buffers)
> return -EIO;
>
> @@ -726,8 +717,8 @@ static int fuse_copy_fill(struct fuse_co
> buf->len = 0;
>
> cs->currbuf = buf;
> - cs->mapaddr = kmap_atomic(page);
> - cs->buf = cs->mapaddr;
> + cs->pg = page;
> + cs->offset = 0;
> cs->len = PAGE_SIZE;
> cs->pipebufs++;
> cs->nr_segs++;
> @@ -740,14 +731,13 @@ static int fuse_copy_fill(struct fuse_co
> cs->iov++;
> cs->nr_segs--;
> }
> - err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
> + err = get_user_pages_fast(cs->addr, 1, cs->write, &page);
> if (err < 0)
> return err;
> BUG_ON(err != 1);
> - offset = cs->addr % PAGE_SIZE;
> - cs->mapaddr = kmap_atomic(cs->pg);
> - cs->buf = cs->mapaddr + offset;
> - cs->len = min(PAGE_SIZE - offset, cs->seglen);
> + cs->pg = page;
> + cs->offset = cs->addr % PAGE_SIZE;
> + cs->len = min(PAGE_SIZE - cs->offset, cs->seglen);
> cs->seglen -= cs->len;
> cs->addr += cs->len;
> }
> @@ -760,15 +750,20 @@ static int fuse_copy_do(struct fuse_copy
> {
> unsigned ncpy = min(*size, cs->len);
> if (val) {
> + void *pgaddr = kmap_atomic(cs->pg);
> + void *buf = pgaddr + cs->offset;
> +
> if (cs->write)
> - memcpy(cs->buf, *val, ncpy);
> + memcpy(buf, *val, ncpy);
> else
> - memcpy(*val, cs->buf, ncpy);
> + memcpy(*val, buf, ncpy);
> +
> + kunmap_atomic(pgaddr);
> *val += ncpy;
> }
> *size -= ncpy;
> cs->len -= ncpy;
> - cs->buf += ncpy;
> + cs->offset += ncpy;
> return ncpy;
> }
>
> @@ -874,8 +869,8 @@ static int fuse_try_move_page(struct fus
> out_fallback_unlock:
> unlock_page(newpage);
> out_fallback:
> - cs->mapaddr = kmap_atomic(buf->page);
> - cs->buf = cs->mapaddr + buf->offset;
> + cs->pg = buf->page;
> + cs->offset = buf->offset;
>
> err = lock_request(cs->fc, cs->req);
> if (err)
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-07-14 15:53 UTC | newest]
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2014-06-25 12:17 [PATCH] fuse: avoid scheduling while atomic Maxim Patlasov
2014-07-04 16:27 ` Miklos Szeredi
2014-07-14 15:53 ` Maxim Patlasov
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