On Mon, Jul 15, 2013 at 12:12:37AM -0400, Theodore Ts'o wrote:
> Some callers of ext4_es_remove_extent() and ext4_es_insert_extent()
> may not be completely robust against ENOMEM failures (or the
> consequences of reflecting ENOMEM back up to userspace may lead to
> xfstest or user application failure).
>
> To mitigate against this, when trying to insert an entry in the extent
> status tree, try to shrink the inode's extent status tree before
> returning ENOMEM. If there are entries which don't record information
> about extents under delayed allocations, freeing one of them is
> preferable to returning ENOMEM.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> Cc: Zheng Liu <wenqing.lz@xxxxxxxxxx>
Thanks for fixing this. The patch looks good to me.
Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
- Zheng
> ---
> fs/ext4/extents_status.c | 51 ++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4b8df7f..91cb110 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -148,6 +148,8 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> ext4_lblk_t end);
> static int __es_try_to_reclaim_extents(struct ext4_inode_info *ei,
> int nr_to_scan);
> +static int __ext4_es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
> + struct ext4_inode_info *locked_ei);
>
> int __init ext4_init_es(void)
> {
> @@ -665,7 +667,13 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
> err = __es_remove_extent(inode, lblk, end);
> if (err != 0)
> goto error;
> +retry:
> err = __es_insert_extent(inode, &newes);
> + if (err == -ENOMEM && __ext4_es_shrink(EXT4_SB(inode->i_sb), 1,
> + EXT4_I(inode)))
> + goto retry;
> + if (err == -ENOMEM && !ext4_es_is_delayed(&newes))
> + err = 0;
>
> error:
> write_unlock(&EXT4_I(inode)->i_es_lock);
> @@ -744,8 +752,10 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> struct extent_status orig_es;
> ext4_lblk_t len1, len2;
> ext4_fsblk_t block;
> - int err = 0;
> + int err;
>
> +retry:
> + err = 0;
> es = __es_tree_search(&tree->root, lblk);
> if (!es)
> goto out;
> @@ -780,6 +790,10 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
> if (err) {
> es->es_lblk = orig_es.es_lblk;
> es->es_len = orig_es.es_len;
> + if ((err == -ENOMEM) &&
> + __ext4_es_shrink(EXT4_SB(inode->i_sb), 1,
> + EXT4_I(inode)))
> + goto retry;
> goto out;
> }
> } else {
> @@ -889,22 +903,14 @@ static int ext4_inode_touch_time_cmp(void *priv, struct list_head *a,
> return -1;
> }
>
> -static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
> +static int __ext4_es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
> + struct ext4_inode_info *locked_ei)
> {
> - struct ext4_sb_info *sbi = container_of(shrink,
> - struct ext4_sb_info, s_es_shrinker);
> struct ext4_inode_info *ei;
> struct list_head *cur, *tmp;
> LIST_HEAD(skiped);
> - int nr_to_scan = sc->nr_to_scan;
> int ret, nr_shrunk = 0;
>
> - ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
> - trace_ext4_es_shrink_enter(sbi->s_sb, nr_to_scan, ret);
> -
> - if (!nr_to_scan)
> - return ret;
> -
> spin_lock(&sbi->s_es_lru_lock);
>
> /*
> @@ -933,7 +939,7 @@ static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
> continue;
> }
>
> - if (ei->i_es_lru_nr == 0)
> + if (ei->i_es_lru_nr == 0 || ei == locked_ei)
> continue;
>
> write_lock(&ei->i_es_lock);
> @@ -952,6 +958,27 @@ static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
> list_splice_tail(&skiped, &sbi->s_es_lru);
> spin_unlock(&sbi->s_es_lru_lock);
>
> + if (locked_ei && nr_shrunk == 0)
> + nr_shrunk = __es_try_to_reclaim_extents(ei, nr_to_scan);
> +
> + return nr_shrunk;
> +}
> +
> +static int ext4_es_shrink(struct shrinker *shrink, struct shrink_control *sc)
> +{
> + struct ext4_sb_info *sbi = container_of(shrink,
> + struct ext4_sb_info, s_es_shrinker);
> + int nr_to_scan = sc->nr_to_scan;
> + int ret, nr_shrunk;
> +
> + ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
> + trace_ext4_es_shrink_enter(sbi->s_sb, nr_to_scan, ret);
> +
> + if (!nr_to_scan)
> + return ret;
> +
> + nr_shrunk = __ext4_es_shrink(sbi, nr_to_scan, NULL);
> +
> ret = percpu_counter_read_positive(&sbi->s_extent_cache_cnt);
> trace_ext4_es_shrink_exit(sbi->s_sb, nr_shrunk, ret);
> return ret;
> --
> 1.7.12.rc0.22.gcdd159b
>
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