From 4be55565fe550febc92af2e26db7d5125f58d3b5 Mon Sep 17 00:00:00 2001 From: Li Wei Date: Thu, 12 Aug 2010 09:24:31 -0700 Subject: [PATCH] Fix stack overflow in vn_rdwr() due to memory reclaim Unless __GFP_IO and __GFP_FS are removed from the file mapping gfp mask we may enter memory reclaim during IO. In this case shrink_slab() entered another file system which is notoriously hungry for stack. This additional stack usage may cause a stack overflow. This patch removes __GFP_IO and __GFP_FS from the mapping gfp mask of each file during vn_open() to avoid any reclaim in the vn_rdwr() IO path. The original mask is then restored at vn_close() time. Hats off to the loop driver which does something similiar for the same reason. [...] shrink_slab+0xdc/0x153 try_to_free_pages+0x1da/0x2d7 __alloc_pages+0x1d7/0x2da do_generic_mapping_read+0x2c9/0x36f file_read_actor+0x0/0x145 __generic_file_aio_read+0x14f/0x19b generic_file_aio_read+0x34/0x39 do_sync_read+0xc7/0x104 vfs_read+0xcb/0x171 :spl:vn_rdwr+0x2b8/0x402 :zfs:vdev_file_io_start+0xad/0xe1 [...] Signed-off-by: Brian Behlendorf --- include/sys/vnode.h | 1 + module/spl/spl-vnode.c | 6 ++++++ 2 files changed, 7 insertions(+) diff --git a/include/sys/vnode.h b/include/sys/vnode.h index 09d843366..104e65d15 100644 --- a/include/sys/vnode.h +++ b/include/sys/vnode.h @@ -180,6 +180,7 @@ typedef struct vnode { struct stdata *v_stream; /* associated stream */ enum vtype v_type; /* vnode type */ dev_t v_rdev; /* device (VCHR, VBLK) */ + gfp_t v_gfp_mask; /* original mapping gfp mask */ } vnode_t; typedef struct vn_file { diff --git a/module/spl/spl-vnode.c b/module/spl/spl-vnode.c index dd759bf7f..29028c3c0 100644 --- a/module/spl/spl-vnode.c +++ b/module/spl/spl-vnode.c @@ -104,6 +104,7 @@ vn_open(const char *path, uio_seg_t seg, int flags, int mode, struct file *fp; struct kstat stat; int rc, saved_umask = 0; + gfp_t saved_gfp; vnode_t *vp; SENTRY; @@ -145,9 +146,13 @@ vn_open(const char *path, uio_seg_t seg, int flags, int mode, SRETURN(ENOMEM); } + saved_gfp = mapping_gfp_mask(fp->f_mapping); + mapping_set_gfp_mask(fp->f_mapping, saved_gfp & ~(__GFP_IO|__GFP_FS)); + mutex_enter(&vp->v_lock); vp->v_type = vn_get_sol_type(stat.mode); vp->v_file = fp; + vp->v_gfp_mask = saved_gfp; *vpp = vp; mutex_exit(&vp->v_lock); @@ -237,6 +242,7 @@ vn_close(vnode_t *vp, int flags, int x1, int x2, void *x3, void *x4) ASSERT(vp); ASSERT(vp->v_file); + mapping_set_gfp_mask(vp->v_file->f_mapping, vp->v_gfp_mask); rc = filp_close(vp->v_file, 0); vn_free(vp);