Linux: always check or verify return of igrab()

zhold() wraps igrab() on Linux, and igrab() may fail when the inode 
is in the process of being deleted.  This means zhold() must only be
called when a reference exists and therefore it cannot be deleted. 
This is the case for all existing consumers so add a VERIFY and a
comment explaining this requirement.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Adam Moss <c@yotes.com>
Closes 
This commit is contained in:
Adam D. Moss 2021-03-16 16:33:34 -07:00 committed by GitHub
parent 5f9d61d06b
commit 1daad98176
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 16 additions and 4 deletions
include/os/linux/zfs/sys
module/os/linux/zfs

View File

@ -73,7 +73,13 @@ extern "C" {
#define zn_has_cached_data(zp) ((zp)->z_is_mapped)
#define zn_rlimit_fsize(zp, uio) (0)
#define zhold(zp) igrab(ZTOI((zp)))
/*
* zhold() wraps igrab() on Linux, and igrab() may fail when the
* inode is in the process of being deleted. As zhold() must only be
* called when a ref already exists - so the inode cannot be
* mid-deletion - we VERIFY() this.
*/
#define zhold(zp) VERIFY3P(igrab(ZTOI((zp))), !=, NULL)
#define zrele(zp) iput(ZTOI((zp)))
/* Called on entry to each ZFS inode and vfs operation. */

View File

@ -590,7 +590,8 @@ struct inode *
zfsctl_root(znode_t *zp)
{
ASSERT(zfs_has_ctldir(zp));
igrab(ZTOZSB(zp)->z_ctldir);
/* Must have an existing ref, so igrab() cannot return NULL */
VERIFY3P(igrab(ZTOZSB(zp)->z_ctldir), !=, NULL);
return (ZTOZSB(zp)->z_ctldir);
}

View File

@ -1734,7 +1734,11 @@ zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp)
VERIFY(zfsctl_root_lookup(*ipp, "snapshot", ipp,
0, kcred, NULL, NULL) == 0);
} else {
igrab(*ipp);
/*
* Must have an existing ref, so igrab()
* cannot return NULL
*/
VERIFY3P(igrab(*ipp), !=, NULL);
}
ZFS_EXIT(zfsvfs);
return (0);

View File

@ -593,7 +593,8 @@ zpl_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
crhold(cr);
ip->i_ctime = current_time(ip);
igrab(ip); /* Use ihold() if available */
/* Must have an existing ref, so igrab() cannot return NULL */
VERIFY3P(igrab(ip), !=, NULL);
cookie = spl_fstrans_mark();
error = -zfs_link(ITOZ(dir), ITOZ(ip), dname(dentry), cr, 0);