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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 #11704
This commit is contained in:
Adam D. Moss 2021-03-16 16:33:34 -07:00 committed by Tony Hutter
parent f14b6f2302
commit ac6f332154
4 changed files with 16 additions and 4 deletions
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8
include/os/linux/zfs/sys/zfs_znode_impl.h
View File

@ -73,7 +73,13 @@ extern "C" {
#define zn_has_cached_data(zp) ((zp)->z_is_mapped)
#define zn_rlimit_fsize(zp, uio, td) (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. */

3
module/os/linux/zfs/zfs_ctldir.c
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);
}

6
module/os/linux/zfs/zfs_vfsops.c
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);

3
module/os/linux/zfs/zpl_inode.c
View File

@ -639,7 +639,8 @@ 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);