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From: Steven Whitehouse on 17 May 2010 09:00
From: Bob Peterson <rpeterso(a)redhat.com>

This patch changes the lock ordering when gfs2 reclaims
unlinked dinodes, thereby avoiding a livelock.

Signed-off-by: Bob Peterson <rpeterso(a)redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho(a)redhat.com>
---
fs/gfs2/rgrp.c | 78 +++++++++++++++++++++----------------------------------
1 files changed, 30 insertions(+), 48 deletions(-)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 3739155..8bce73e 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -952,16 +952,14 @@ static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
* The inode, if one has been found, in inode.
*/

-static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
- u64 skip, struct inode **inode)
+static u64 try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
+ u64 skip)
{
u32 goal = 0, block;
u64 no_addr;
struct gfs2_sbd *sdp = rgd->rd_sbd;
unsigned int n;
- int error = 0;

- *inode = NULL;
for(;;) {
if (goal >= rgd->rd_data)
break;
@@ -981,10 +979,7 @@ static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
if (no_addr == skip)
continue;
*last_unlinked = no_addr;
- error = gfs2_unlinked_inode_lookup(rgd->rd_sbd->sd_vfs,
- no_addr, inode);
- if (*inode || error)
- return error;
+ return no_addr;
}

rgd->rd_flags &= ~GFS2_RDF_CHECK;
@@ -1069,11 +1064,12 @@ static void forward_rgrp_set(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd)
* Try to acquire rgrp in way which avoids contending with others.
*
* Returns: errno
+ * unlinked: the block address of an unlinked block to be reclaimed
*/

-static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
+static int get_local_rgrp(struct gfs2_inode *ip, u64 *unlinked,
+ u64 *last_unlinked)
{
- struct inode *inode = NULL;
struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
struct gfs2_rgrpd *rgd, *begin = NULL;
struct gfs2_alloc *al = ip->i_alloc;
@@ -1082,6 +1078,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
int loops = 0;
int error, rg_locked;

+ *unlinked = 0;
rgd = gfs2_blk2rgrpd(sdp, ip->i_goal);

while (rgd) {
@@ -1103,29 +1100,19 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
because that would require an iput which can only
happen after the rgrp is unlocked. */
if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
- error = try_rgrp_unlink(rgd, last_unlinked,
- ip->i_no_addr, &inode);
+ *unlinked = try_rgrp_unlink(rgd, last_unlinked,
+ ip->i_no_addr);
if (!rg_locked)
gfs2_glock_dq_uninit(&al->al_rgd_gh);
- if (inode) {
- if (error) {
- if (inode->i_state & I_NEW)
- iget_failed(inode);
- else
- iput(inode);
- return ERR_PTR(error);
- }
- return inode;
- }
- if (error)
- return ERR_PTR(error);
+ if (*unlinked)
+ return -EAGAIN;
/* fall through */
case GLR_TRYFAILED:
rgd = recent_rgrp_next(rgd);
break;

default:
- return ERR_PTR(error);
+ return error;
}
}

@@ -1148,22 +1135,12 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
if (try_rgrp_fit(rgd, al))
goto out;
if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
- error = try_rgrp_unlink(rgd, last_unlinked,
- ip->i_no_addr, &inode);
+ *unlinked = try_rgrp_unlink(rgd, last_unlinked,
+ ip->i_no_addr);
if (!rg_locked)
gfs2_glock_dq_uninit(&al->al_rgd_gh);
- if (inode) {
- if (error) {
- if (inode->i_state & I_NEW)
- iget_failed(inode);
- else
- iput(inode);
- return ERR_PTR(error);
- }
- return inode;
- }
- if (error)
- return ERR_PTR(error);
+ if (*unlinked)
+ return -EAGAIN;
break;

case GLR_TRYFAILED:
@@ -1171,7 +1148,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
break;

default:
- return ERR_PTR(error);
+ return error;
}

rgd = gfs2_rgrpd_get_next(rgd);
@@ -1180,7 +1157,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)

if (rgd == begin) {
if (++loops >= 3)
- return ERR_PTR(-ENOSPC);
+ return -ENOSPC;
if (!skipped)
loops++;
flags = 0;
@@ -1200,7 +1177,7 @@ out:
forward_rgrp_set(sdp, rgd);
}

- return NULL;
+ return 0;
}

/**
@@ -1216,7 +1193,7 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
struct gfs2_alloc *al = ip->i_alloc;
struct inode *inode;
int error = 0;
- u64 last_unlinked = NO_BLOCK;
+ u64 last_unlinked = NO_BLOCK, unlinked;

if (gfs2_assert_warn(sdp, al->al_requested))
return -EINVAL;
@@ -1232,14 +1209,19 @@ try_again:
if (error)
return error;

- inode = get_local_rgrp(ip, &last_unlinked);
- if (inode) {
+ error = get_local_rgrp(ip, &unlinked, &last_unlinked);
+ if (error) {
if (ip != GFS2_I(sdp->sd_rindex))
gfs2_glock_dq_uninit(&al->al_ri_gh);
- if (IS_ERR(inode))
- return PTR_ERR(inode);
- iput(inode);
+ if (error != -EAGAIN)
+ return error;
+ error = gfs2_unlinked_inode_lookup(ip->i_inode.i_sb,
+ unlinked, &inode);
+ if (inode)
+ iput(inode);
gfs2_log_flush(sdp, NULL);
+ if (error == GLR_TRYFAILED)
+ error = 0;
goto try_again;
}

--
1.6.2.5

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Prev: [PATCH 07/11] GFS2: Add some useful messages
Next: [PATCH 06/11] GFS2: fix quota state reporting