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Message-ID: <Zz_k4CtwOKGUbr6V@dread.disaster.area>
Date: Fri, 22 Nov 2024 12:56:48 +1100
From: Dave Chinner <david@...morbit.com>
To: Christian Brauner <brauner@...nel.org>
Cc: Mateusz Guzik <mjguzik@...il.com>, viro@...iv.linux.org.uk,
jack@...e.cz, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, hughd@...gle.com,
linux-ext4@...r.kernel.org, tytso@....edu, linux-mm@...ck.org
Subject: Re: [PATCH v3 1/3] vfs: support caching symlink lengths in inodes
On Thu, Nov 21, 2024 at 11:12:52AM +0100, Christian Brauner wrote:
> I think that i_devices should be moved into the union as it's really
> only used with i_cdev but it's not that easily done because list_head
> needs to be initialized.
I'm planning on using i_devices with block devices, too, so the
block device list doesn't need to use i_sb_list anymore (similar to
how i_devices is used by the char dev infrastructure. See the patch
below...
> I roughly envisioned something like:
>
> union {
> struct {
> struct cdev *i_cdev;
> struct list_head i_devices;
> };
> struct {
> char *i_link;
> unsigned int i_link_len;
> };
> struct pipe_inode_info *i_pipe;
> unsigned i_dir_seq;
> };
>
I'd probably have to undo any unioning/association with i_cdev to
use i_devices with block devs...
-Dave
--
Dave Chinner
david@...morbit.com
bdev: stop using sb->s_inodes
From: Dave Chinner <dchinner@...hat.com>
Iteration of block device inodes is done via the
blockdev_superblock->s_inodes list. We want to remove this list and
the inode i_sb_list list heads, so we need some other way for block
devices to be iterated.
Take a leaf from the chardev code and use the inode->i_devices list
head to link all the block device inodes together and replace the
s_inodes list with a bdev private global list.
Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
block/bdev.c | 56 +++++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 39 insertions(+), 17 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index 33f9c4605e3a..d733507f584a 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -317,6 +317,8 @@ EXPORT_SYMBOL(bdev_thaw);
static __cacheline_aligned_in_smp DEFINE_MUTEX(bdev_lock);
static struct kmem_cache *bdev_cachep __ro_after_init;
+static LIST_HEAD(bdev_inodes);
+static DEFINE_SPINLOCK(bdev_inodes_lock);
static struct inode *bdev_alloc_inode(struct super_block *sb)
{
@@ -362,6 +364,10 @@ static void init_once(void *data)
static void bdev_evict_inode(struct inode *inode)
{
+ spin_lock(&bdev_inodes_lock);
+ list_del_init(&inode->i_devices);
+ spin_unlock(&bdev_inodes_lock);
+
truncate_inode_pages_final(&inode->i_data);
invalidate_inode_buffers(inode); /* is it needed here? */
clear_inode(inode);
@@ -412,19 +418,35 @@ void __init bdev_cache_init(void)
blockdev_superblock = blockdev_mnt->mnt_sb; /* For writeback */
}
-struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
+static struct inode *bdev_new_inode(void)
{
- struct block_device *bdev;
struct inode *inode;
- inode = new_inode(blockdev_superblock);
+ inode = new_inode_pseudo(blockdev_superblock);
if (!inode)
return NULL;
+
+ spin_lock(&bdev_inodes_lock);
+ list_add(&inode->i_devices, &bdev_inodes);
+ spin_unlock(&bdev_inodes_lock);
+
inode->i_mode = S_IFBLK;
inode->i_rdev = 0;
inode->i_data.a_ops = &def_blk_aops;
mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+ return inode;
+}
+
+struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
+{
+ struct block_device *bdev;
+ struct inode *inode;
+
+ inode = bdev_new_inode();
+ if (!inode)
+ return NULL;
+
bdev = I_BDEV(inode);
mutex_init(&bdev->bd_fsfreeze_mutex);
spin_lock_init(&bdev->bd_size_lock);
@@ -477,10 +499,10 @@ long nr_blockdev_pages(void)
struct inode *inode;
long ret = 0;
- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
+ spin_lock(&bdev_inodes_lock);
+ list_for_each_entry(inode, &bdev_inodes, i_devices)
ret += inode->i_mapping->nrpages;
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
+ spin_unlock(&bdev_inodes_lock);
return ret;
}
@@ -1218,8 +1240,8 @@ void sync_bdevs(bool wait)
{
struct inode *inode, *old_inode = NULL;
- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
+ spin_lock(&bdev_inodes_lock);
+ list_for_each_entry(inode, &bdev_inodes, i_devices) {
struct address_space *mapping = inode->i_mapping;
struct block_device *bdev;
@@ -1231,14 +1253,14 @@ void sync_bdevs(bool wait)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
+ spin_unlock(&bdev_inodes_lock);
+
/*
- * We hold a reference to 'inode' so it couldn't have been
- * removed from s_inodes list while we dropped the
- * s_inode_list_lock We cannot iput the inode now as we can
- * be holding the last reference and we cannot iput it under
- * s_inode_list_lock. So we keep the reference and iput it
- * later.
+ * We hold a reference to 'inode' so it won't get removed from
+ * bdev inodes list while we drop the lock. We need to hold the
+ * reference until we have a reference on the next inode on the
+ * list, so we can't drop it until the next time we let go of
+ * the bdev_inodes_lock.
*/
iput(old_inode);
old_inode = inode;
@@ -1260,9 +1282,9 @@ void sync_bdevs(bool wait)
}
mutex_unlock(&bdev->bd_disk->open_mutex);
- spin_lock(&blockdev_superblock->s_inode_list_lock);
+ spin_lock(&bdev_inodes_lock);
}
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
+ spin_unlock(&bdev_inodes_lock);
iput(old_inode);
}
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