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Linux: always check or verify return of igrab()

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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);