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authorLukas Czerner <lczerner@redhat.com>2013-02-22 15:27:52 -0500
committerTheodore Ts'o <tytso@mit.edu>2013-02-22 15:27:52 -0500
commit304e220f0879198b1f5309ad6f0be862b4009491 (patch)
tree2a55e650498dc76c356fa0caf174d47506dacc28 /fs/ext4
parentd43814721111041e26671a153e300e2054fb36fa (diff)
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ext4: fix free clusters calculation in bigalloc filesystem
ext4_has_free_clusters() should tell us whether there is enough free clusters to allocate, however number of free clusters in the file system is converted to blocks using EXT4_C2B() which is not only wrong use of the macro (we should have used EXT4_NUM_B2C) but it's also completely wrong concept since everything else is in cluster units. Moreover when calculating number of root clusters we should be using macro EXT4_NUM_B2C() instead of EXT4_B2C() otherwise the result might be off by one. However r_blocks_count should always be a multiple of the cluster ratio so doing a plain bit shift should be enough here. We avoid using EXT4_B2C() because it's confusing. As a result of the first problem number of free clusters is much bigger than it should have been and ext4_has_free_clusters() would return 1 even if there is really not enough free clusters available. Fix this by removing the EXT4_C2B() conversion of free clusters and using bit shift when calculating number of root clusters. This bug affects number of xfstests tests covering file system ENOSPC situation handling. With this patch most of the ENOSPC problems with bigalloc file system disappear, especially the errors caused by delayed allocation not having enough space when the actual allocation is finally requested. Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/balloc.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 33938c1..2f2e0da 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -484,11 +484,16 @@ static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
free_clusters = percpu_counter_read_positive(fcc);
dirty_clusters = percpu_counter_read_positive(dcc);
- root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
+
+ /*
+ * r_blocks_count should always be multiple of the cluster ratio so
+ * we are safe to do a plane bit shift only.
+ */
+ root_clusters = ext4_r_blocks_count(sbi->s_es) >> sbi->s_cluster_bits;
if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
EXT4_FREECLUSTERS_WATERMARK) {
- free_clusters = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
+ free_clusters = percpu_counter_sum_positive(fcc);
dirty_clusters = percpu_counter_sum_positive(dcc);
}
/* Check whether we have space after accounting for current