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NFSv4.1: Fix pnfs_put_lseg races

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pnfs_layoutreturn_free_lseg_async() can also race with inode put in
the general case. We can now fix this, and also simplify the code.

Cc: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Trond Myklebust 2015-02-05 17:27:39 -05:00
parent e4af440aaf
commit 4ef2e4f84c
1 changed files with 19 additions and 34 deletions
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53
fs/nfs/pnfs.c
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@ -361,14 +361,9 @@ pnfs_layout_need_return(struct pnfs_layout_hdr *lo,
return true; return true;
} }
static void pnfs_layoutreturn_free_lseg(struct work_struct *work) static void pnfs_layoutreturn_before_put_lseg(struct pnfs_layout_segment *lseg,
struct pnfs_layout_hdr *lo, struct inode *inode)
{ {
struct pnfs_layout_segment *lseg;
struct pnfs_layout_hdr *lo;
struct inode *inode;
lseg = container_of(work, struct pnfs_layout_segment, pls_work);
WARN_ON(atomic_read(&lseg->pls_refcount));
lo = lseg->pls_layout; lo = lseg->pls_layout;
inode = lo->plh_inode; inode = lo->plh_inode;
@ -383,24 +378,12 @@ static void pnfs_layoutreturn_free_lseg(struct work_struct *work)
lo->plh_block_lgets++; lo->plh_block_lgets++;
lo->plh_return_iomode = 0; lo->plh_return_iomode = 0;
spin_unlock(&inode->i_lock); spin_unlock(&inode->i_lock);
pnfs_get_layout_hdr(lo);
pnfs_send_layoutreturn(lo, stateid, iomode, true); /* Send an async layoutreturn so we dont deadlock */
spin_lock(&inode->i_lock); pnfs_send_layoutreturn(lo, stateid, iomode, false);
} else } else
/* match pnfs_get_layout_hdr #2 in pnfs_put_lseg */ spin_unlock(&inode->i_lock);
pnfs_put_layout_hdr(lo);
pnfs_layout_remove_lseg(lo, lseg);
spin_unlock(&inode->i_lock);
pnfs_free_lseg(lseg);
/* match pnfs_get_layout_hdr #1 in pnfs_put_lseg */
pnfs_put_layout_hdr(lo);
}
static void
pnfs_layoutreturn_free_lseg_async(struct pnfs_layout_segment *lseg)
{
INIT_WORK(&lseg->pls_work, pnfs_layoutreturn_free_lseg);
queue_work(nfsiod_workqueue, &lseg->pls_work);
} }
void void
@ -415,21 +398,23 @@ pnfs_put_lseg(struct pnfs_layout_segment *lseg)
dprintk("%s: lseg %p ref %d valid %d\n", __func__, lseg, dprintk("%s: lseg %p ref %d valid %d\n", __func__, lseg,
atomic_read(&lseg->pls_refcount), atomic_read(&lseg->pls_refcount),
test_bit(NFS_LSEG_VALID, &lseg->pls_flags)); test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
/* Handle the case where refcount != 1 */
if (atomic_add_unless(&lseg->pls_refcount, -1, 1))
return;
lo = lseg->pls_layout; lo = lseg->pls_layout;
inode = lo->plh_inode; inode = lo->plh_inode;
/* Do we need a layoutreturn? */
if (test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags))
pnfs_layoutreturn_before_put_lseg(lseg, lo, inode);
if (atomic_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) { if (atomic_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) {
pnfs_get_layout_hdr(lo); pnfs_get_layout_hdr(lo);
if (pnfs_layout_need_return(lo, lseg)) { pnfs_layout_remove_lseg(lo, lseg);
spin_unlock(&inode->i_lock); spin_unlock(&inode->i_lock);
/* hdr reference dropped in nfs4_layoutreturn_release */ pnfs_free_lseg(lseg);
pnfs_get_layout_hdr(lo); pnfs_put_layout_hdr(lo);
pnfs_layoutreturn_free_lseg_async(lseg);
} else {
pnfs_layout_remove_lseg(lo, lseg);
spin_unlock(&inode->i_lock);
pnfs_free_lseg(lseg);
pnfs_put_layout_hdr(lo);
}
} }
} }
EXPORT_SYMBOL_GPL(pnfs_put_lseg); EXPORT_SYMBOL_GPL(pnfs_put_lseg);