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Message-ID: <20250414060125.19938-2-heming.zhao@suse.com>
Date: Mon, 14 Apr 2025 14:01:23 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: joseph.qi@...ux.alibaba.com
Cc: Heming Zhao <heming.zhao@...e.com>,
ocfs2-devel@...ts.linux.dev,
linux-kernel@...r.kernel.org,
gautham.ananthakrishna@...cle.com
Subject: [PATCH v2 1/1] ocfs2: fix the issue with discontiguous allocation in the global_bitmap
The commit 4eb7b93e0310 ("ocfs2: improve write IO performance when
fragmentation is high") introduced another regression.
The following ocfs2-test case can trigger this issue:
> discontig_runner.sh => activate_discontig_bg.sh => resv_unwritten:
> ${RESV_UNWRITTEN_BIN} -f ${WORK_PLACE}/large_testfile -s 0 -l \
> $((${FILE_MAJOR_SIZE_M}*1024*1024))
In my env, test disk size (by "fdisk -l <dev>"):
> 53687091200 bytes, 104857600 sectors.
Above command is:
> /usr/local/ocfs2-test/bin/resv_unwritten -f \
> /mnt/ocfs2/ocfs2-activate-discontig-bg-dir/large_testfile -s 0 -l \
> 53187969024
Error log:
> [*] Reserve 50724M space for a LARGE file, reserve 200M space for future test.
> ioctl error 28: "No space left on device"
> resv allocation failed Unknown error -1
> reserve unwritten region from 0 to 53187969024.
Call flow:
__ocfs2_change_file_space //by ioctl OCFS2_IOC_RESVSP64
ocfs2_allocate_unwritten_extents //start:0 len:53187969024
while()
+ ocfs2_get_clusters //cpos:0, alloc_size:1623168 (cluster number)
+ ocfs2_extend_allocation
+ ocfs2_lock_allocators
| + choose OCFS2_AC_USE_MAIN & ocfs2_cluster_group_search
|
+ ocfs2_add_inode_data
ocfs2_add_clusters_in_btree
__ocfs2_claim_clusters
ocfs2_claim_suballoc_bits
+ During the allocation of the final part of the large file
(after ~47GB), no chain had the required contiguous
bits_wanted. Consequently, the allocation failed.
How to fix:
When OCFS2 is encountering fragmented allocation, the file system should
stop attempting bits_wanted contiguous allocation and instead provide the
largest available contiguous free bits from the cluster groups.
Reported-by: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
Signed-off-by: Heming Zhao <heming.zhao@...e.com>
Fixes: 4eb7b93e0310 ("ocfs2: improve write IO performance when fragmentation is high")
---
fs/ocfs2/suballoc.c | 38 ++++++++++++++++++++++++++++++++------
fs/ocfs2/suballoc.h | 1 +
2 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index f7b483f0de2a..6ac4dcd54588 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -698,10 +698,12 @@ static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
bg_bh = ocfs2_block_group_alloc_contig(osb, handle, alloc_inode,
ac, cl);
- if (PTR_ERR(bg_bh) == -ENOSPC)
+ if (PTR_ERR(bg_bh) == -ENOSPC) {
+ ac->ac_which = OCFS2_AC_USE_MAIN_DISCONTIG;
bg_bh = ocfs2_block_group_alloc_discontig(handle,
alloc_inode,
ac, cl);
+ }
if (IS_ERR(bg_bh)) {
status = PTR_ERR(bg_bh);
bg_bh = NULL;
@@ -1794,6 +1796,7 @@ static int ocfs2_search_chain(struct ocfs2_alloc_context *ac,
{
int status;
u16 chain;
+ u32 contig_bits;
u64 next_group;
struct inode *alloc_inode = ac->ac_inode;
struct buffer_head *group_bh = NULL;
@@ -1819,10 +1822,21 @@ static int ocfs2_search_chain(struct ocfs2_alloc_context *ac,
status = -ENOSPC;
/* for now, the chain search is a bit simplistic. We just use
* the 1st group with any empty bits. */
- while ((status = ac->ac_group_search(alloc_inode, group_bh,
- bits_wanted, min_bits,
- ac->ac_max_block,
- res)) == -ENOSPC) {
+ while (1) {
+ if (ac->ac_which == OCFS2_AC_USE_MAIN_DISCONTIG) {
+ contig_bits = le16_to_cpu(bg->bg_contig_free_bits);
+ if (!contig_bits)
+ contig_bits = ocfs2_find_max_contig_free_bits(bg->bg_bitmap,
+ le16_to_cpu(bg->bg_bits), 0);
+ if (bits_wanted > contig_bits && contig_bits >= min_bits)
+ bits_wanted = contig_bits;
+ }
+
+ status = ac->ac_group_search(alloc_inode, group_bh,
+ bits_wanted, min_bits,
+ ac->ac_max_block, res);
+ if (status != -ENOSPC)
+ break;
if (!bg->bg_next_group)
break;
@@ -1982,6 +1996,7 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
victim = ocfs2_find_victim_chain(cl);
ac->ac_chain = victim;
+search:
status = ocfs2_search_chain(ac, handle, bits_wanted, min_bits,
res, &bits_left);
if (!status) {
@@ -2022,6 +2037,16 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
}
}
+ /* Chains can't supply the bits_wanted contiguous space.
+ * We should switch to using every single bit when allocating
+ * from the global bitmap. */
+ if (i == le16_to_cpu(cl->cl_next_free_rec) &&
+ status == -ENOSPC && ac->ac_which == OCFS2_AC_USE_MAIN) {
+ ac->ac_which = OCFS2_AC_USE_MAIN_DISCONTIG;
+ ac->ac_chain = victim;
+ goto search;
+ }
+
set_hint:
if (status != -ENOSPC) {
/* If the next search of this group is not likely to
@@ -2365,7 +2390,8 @@ int __ocfs2_claim_clusters(handle_t *handle,
BUG_ON(ac->ac_bits_given >= ac->ac_bits_wanted);
BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL
- && ac->ac_which != OCFS2_AC_USE_MAIN);
+ && ac->ac_which != OCFS2_AC_USE_MAIN
+ && ac->ac_which != OCFS2_AC_USE_MAIN_DISCONTIG);
if (ac->ac_which == OCFS2_AC_USE_LOCAL) {
WARN_ON(min_clusters > 1);
diff --git a/fs/ocfs2/suballoc.h b/fs/ocfs2/suballoc.h
index b481b834857d..bcf2ed4a8631 100644
--- a/fs/ocfs2/suballoc.h
+++ b/fs/ocfs2/suballoc.h
@@ -29,6 +29,7 @@ struct ocfs2_alloc_context {
#define OCFS2_AC_USE_MAIN 2
#define OCFS2_AC_USE_INODE 3
#define OCFS2_AC_USE_META 4
+#define OCFS2_AC_USE_MAIN_DISCONTIG 5
u32 ac_which;
/* these are used by the chain search */
--
2.43.0
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