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Fix z_xattr_lock/z_teardown_lock inversion 

There exists a lock inversion between the z_xattr_lock and the
z_teardown_lock.  Resolve this by taking the z_teardown_lock in
all registered xattr callbacks prior to taking the z_xattr_lock.
This ensures the locks are always taken is the same order thus
preventing a deadlock.  Note the z_teardown_lock is taken again
in zfs_lookup() and this is safe because the z_teardown lock is
a re-entrant read reader/writer lock.

* process-1
zpl_xattr_get -> Takes zp->z_xattr_lock
  __zpl_xattr_get
    zfs_lookup -> Takes zsb->z_teardown_lock in ZFS_ENTER macro

* process-2
zfs_ioc_recv -> Takes zsb->z_teardown_lock in zfs_suspend_fs()
  zfs_resume_fs
    zfs_rezget -> Takes zp->z_xattr_lock

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Closes #3943
Closes #3969
Closes #4121
This commit is contained in:
Brian Behlendorf 2015-12-21 09:27:24 -08:00 committed by Ned Bass
parent 44f547af98
commit 3445a340d5
1 changed files with 7 additions and 0 deletions
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7
module/zfs/zpl_xattr.c
View File

@ -214,6 +214,7 @@ zpl_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
crhold(cr);
cookie = spl_fstrans_mark();
rrm_enter_read(&(zsb)->z_teardown_lock, FTAG);
rw_enter(&zp->z_xattr_lock, RW_READER);
if (zsb->z_use_sa && zp->z_is_sa) {
@ -230,6 +231,7 @@ zpl_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
out:
rw_exit(&zp->z_xattr_lock);
rrm_exit(&(zsb)->z_teardown_lock, FTAG);
spl_fstrans_unmark(cookie);
crfree(cr);
@ -339,15 +341,18 @@ static int
zpl_xattr_get(struct inode *ip, const char *name, void *value, size_t size)
{
znode_t *zp = ITOZ(ip);
zfs_sb_t *zsb = ZTOZSB(zp);
cred_t *cr = CRED();
fstrans_cookie_t cookie;
int error;
crhold(cr);
cookie = spl_fstrans_mark();
rrm_enter_read(&(zsb)->z_teardown_lock, FTAG);
rw_enter(&zp->z_xattr_lock, RW_READER);
error = __zpl_xattr_get(ip, name, value, size, cr);
rw_exit(&zp->z_xattr_lock);
rrm_exit(&(zsb)->z_teardown_lock, FTAG);
spl_fstrans_unmark(cookie);
crfree(cr);
@ -493,6 +498,7 @@ zpl_xattr_set(struct inode *ip, const char *name, const void *value,
crhold(cr);
cookie = spl_fstrans_mark();
rrm_enter_read(&(zsb)->z_teardown_lock, FTAG);
rw_enter(&ITOZ(ip)->z_xattr_lock, RW_WRITER);
/*
@ -530,6 +536,7 @@ zpl_xattr_set(struct inode *ip, const char *name, const void *value,
error = zpl_xattr_set_dir(ip, name, value, size, flags, cr);
out:
rw_exit(&ITOZ(ip)->z_xattr_lock);
rrm_exit(&(zsb)->z_teardown_lock, FTAG);
spl_fstrans_unmark(cookie);
crfree(cr);
ASSERT3S(error, <=, 0);