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Use KM_PUSHPAGE instead of KM_SLEEP

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It used to be the case that all KM_SLEEP allocations were GFS_NOFS.
Unfortunately this often resulted in the kernel being unable to
reclaim the ARC, inode, and dentry caches in a timely manor.
The fix was to make KM_SLEEP a GFP_KERNEL allocation in the SPL.

However, this increases the posibility of deadlocking the system
on a zfs write thread.  If a zfs write thread attempts to perform
an allocation it may trigger synchronous reclaim.  This reclaim
may attempt to flush dirty data/inode to disk to free memory.
Unforunately, this write cannot finish because the write thread
which would handle it is holding the previous transaction open.
Deadlock.

To avoid this all allocations in the zfs write thread path must
use KM_PUSHPAGE which prohibits synchronous reclaim for that
thread.  In this way forward progress in ensured.  The risk
with this change is I missed updating an allocation for the
write threads leaving an increased posibility of deadlock.  If
any deadlocks remain they will be unlikely but we'll have to
make sure they all get fixed.
This commit is contained in:
Brian Behlendorf 2011-03-19 14:34:30 -07:00
parent f47c42e214
commit 691f6ac4c2
3 changed files with 9 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
module/zfs/arc.c
View File

@ -2720,7 +2720,7 @@ arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
arc_callback_t *acb = NULL;
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_SLEEP);
KM_PUSHPAGE);
acb->acb_done = done;
acb->acb_private = private;
if (pio != NULL)
@ -2836,7 +2836,7 @@ arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
ASSERT(!GHOST_STATE(hdr->b_state));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
acb = kmem_zalloc(sizeof (arc_callback_t), KM_PUSHPAGE);
acb->acb_done = done;
acb->acb_private = private;
@ -2885,7 +2885,7 @@ arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
ARCSTAT_BUMP(arcstat_l2_hits);
cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
KM_SLEEP);
KM_PUSHPAGE);
cb->l2rcb_buf = buf;
cb->l2rcb_spa = spa;
cb->l2rcb_bp = *bp;

4
module/zfs/zfs_znode.c
View File

@ -174,7 +174,7 @@ zfs_create_share_dir(zfs_sb_t *zsb, dmu_tx_t *tx)
vattr.va_uid = crgetuid(kcred);
vattr.va_gid = crgetgid(kcred);
sharezp = kmem_cache_alloc(znode_cache, KM_SLEEP);
sharezp = kmem_cache_alloc(znode_cache, KM_PUSHPAGE);
sharezp->z_moved = 0;
sharezp->z_unlinked = 0;
sharezp->z_atime_dirty = 0;
@ -248,7 +248,7 @@ zfs_inode_alloc(struct super_block *sb, struct inode **ip)
{
znode_t *zp;
zp = kmem_cache_alloc(znode_cache, KM_SLEEP);
zp = kmem_cache_alloc(znode_cache, KM_PUSHPAGE);
*ip = ZTOI(zp);
return (0);

8
module/zfs/zio.c
View File

@ -255,7 +255,7 @@ static void
zio_push_transform(zio_t *zio, void *data, uint64_t size, uint64_t bufsize,
zio_transform_func_t *transform)
{
zio_transform_t *zt = kmem_alloc(sizeof (zio_transform_t), KM_SLEEP);
zio_transform_t *zt = kmem_alloc(sizeof (zio_transform_t), KM_PUSHPAGE);
zt->zt_orig_data = zio->io_data;
zt->zt_orig_size = zio->io_size;
@ -370,7 +370,7 @@ zio_unique_parent(zio_t *cio)
void
zio_add_child(zio_t *pio, zio_t *cio)
{
zio_link_t *zl = kmem_cache_alloc(zio_link_cache, KM_SLEEP);
zio_link_t *zl = kmem_cache_alloc(zio_link_cache, KM_PUSHPAGE);
int w;
/*
@ -491,7 +491,7 @@ zio_create(zio_t *pio, spa_t *spa, uint64_t txg, const blkptr_t *bp,
ASSERT(!bp || !(flags & ZIO_FLAG_CONFIG_WRITER));
ASSERT(vd || stage == ZIO_STAGE_OPEN);
zio = kmem_cache_alloc(zio_cache, KM_SLEEP);
zio = kmem_cache_alloc(zio_cache, KM_PUSHPAGE);
bzero(zio, sizeof (zio_t));
mutex_init(&zio->io_lock, NULL, MUTEX_DEFAULT, NULL);
@ -1503,7 +1503,7 @@ zio_gang_node_alloc(zio_gang_node_t **gnpp)
ASSERT(*gnpp == NULL);
gn = kmem_zalloc(sizeof (*gn), KM_SLEEP);
gn = kmem_zalloc(sizeof (*gn), KM_PUSHPAGE);
gn->gn_gbh = zio_buf_alloc(SPA_GANGBLOCKSIZE);
*gnpp = gn;