[PATCH 3.15 011/109] fuse: avoid scheduling while atomic

Greg Kroah-Hartman
2014-07-26T19:13:24Z

From: Miklos Szeredi <mszeredi@suse.cz>

commit c55a01d360afafcd52bc405c044a6ebf5de436d5 upstream.

As reported by Richard Sharpe, an attempt to use fuse_notify_inval_entry()
triggers complains about scheduling while atomic:

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().

Introduced by commit 58bda1da4b3c "fuse/dev: use atomic maps"

Fix by moving the map/unmap to just cover the actual memcpy operation.

Original patch from Maxim Patlasov <mpatlasov@parallels.com>

Reported-by: Richard Sharpe <realrichardsharpe@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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)