ext4: limit the maximum folio order

In environments with a page size of 64KB, the maximum size of a folio
can reach up to 128MB. Consequently, during the write-back of folios,
the 'rsv_blocks' will be overestimated to 1,577, which can make
pressure on the journal space where the journal is small. This can
easily exceed the limit of a single transaction. Besides, an excessively
large folio is meaningless and will instead increase the overhead of
traversing the bhs within the folio. Therefore, limit the maximum order
of a folio to 2048 filesystem blocks.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Joseph Qi <jiangqi903@gmail.com>
Closes: https://lore.kernel.org/linux-ext4/CA+G9fYsyYQ3ZL4xaSg1-Tt5Evto7Zd+hgNWZEa9cQLbahA1+xg@mail.gmail.com/
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Tested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250707140814.542883-12-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f705046ba6c671a44388e67151af24e91df5b31e..9ac0a7d4fa0cd7b54ff9966310f6ddf4d8d69d09 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3020,7 +3020,7 @@ int ext4_walk_page_buffers(handle_t *handle,
                                     struct buffer_head *bh));
 int do_journal_get_write_access(handle_t *handle, struct inode *inode,
                                struct buffer_head *bh);
-bool ext4_should_enable_large_folio(struct inode *inode);
+void ext4_set_inode_mapping_order(struct inode *inode);
 #define FALL_BACK_TO_NONDELALLOC 1
 #define CONVERT_INLINE_DATA     2
 

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 79aa3df8d0197b227cb9d5af401556bd15bed3d0..df4051613b290a78728176d3b8198ad90de84977 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1335,8 +1335,7 @@ got:
                }
        }
 
-       if (ext4_should_enable_large_folio(inode))
-               mapping_set_large_folios(inode->i_mapping);
+       ext4_set_inode_mapping_order(inode);
 
        ext4_update_inode_fsync_trans(handle, inode, 1);
 

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4a0ba009c88e763ea7f460bf8b6e148d4e24644d..8bdf2029ebc746469138ece1b02621606752cc91 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5179,7 +5179,7 @@ error:
        return -EFSCORRUPTED;
 }
 
-bool ext4_should_enable_large_folio(struct inode *inode)
+static bool ext4_should_enable_large_folio(struct inode *inode)
 {
        struct super_block *sb = inode->i_sb;
 
@@ -5196,6 +5196,22 @@ bool ext4_should_enable_large_folio(struct inode *inode)
        return true;
 }
 
+/*
+ * Limit the maximum folio order to 2048 blocks to prevent overestimation
+ * of reserve handle credits during the folio writeback in environments
+ * where the PAGE_SIZE exceeds 4KB.
+ */
+#define EXT4_MAX_PAGECACHE_ORDER(i)            \
+               umin(MAX_PAGECACHE_ORDER, (11 + (i)->i_blkbits - PAGE_SHIFT))
+void ext4_set_inode_mapping_order(struct inode *inode)
+{
+       if (!ext4_should_enable_large_folio(inode))
+               return;
+
+       mapping_set_folio_order_range(inode->i_mapping, 0,
+                                     EXT4_MAX_PAGECACHE_ORDER(inode));
+}
+
 struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
                          ext4_iget_flags flags, const char *function,
                          unsigned int line)
@@ -5513,8 +5529,8 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
                ret = -EFSCORRUPTED;
                goto bad_inode;
        }
-       if (ext4_should_enable_large_folio(inode))
-               mapping_set_large_folios(inode->i_mapping);
+
+       ext4_set_inode_mapping_order(inode);
 
        ret = check_igot_inode(inode, flags, function, line);
        /*