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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 <behlendorf1@llnl.gov>
This commit is contained in:
Li Wei 2010-08-12 09:24:31 -07:00 committed by Brian Behlendorf
parent 46aa7b3939
commit 4be55565fe
2 changed files with 7 additions and 0 deletions
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1
include/sys/vnode.h
View File

@ -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 {

6
module/spl/spl-vnode.c
View File

@ -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);