[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20241024132225.2271667-7-yukuai1@huaweicloud.com>
Date: Thu, 24 Oct 2024 21:22:19 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: stable@...r.kernel.org,
gregkh@...uxfoundation.org,
harry.wentland@....com,
sunpeng.li@....com,
Rodrigo.Siqueira@....com,
alexander.deucher@....com,
christian.koenig@....com,
Xinhui.Pan@....com,
airlied@...il.com,
daniel@...ll.ch,
viro@...iv.linux.org.uk,
brauner@...nel.org,
Liam.Howlett@...cle.com,
akpm@...ux-foundation.org,
hughd@...gle.com,
willy@...radead.org,
sashal@...nel.org,
srinivasan.shanmugam@....com,
chiahsuan.chung@....com,
mingo@...nel.org,
mgorman@...hsingularity.net,
yukuai3@...wei.com,
chengming.zhou@...ux.dev,
zhangpeng.00@...edance.com,
chuck.lever@...cle.com
Cc: amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
maple-tree@...ts.infradead.org,
linux-mm@...ck.org,
yukuai1@...weicloud.com,
yi.zhang@...wei.com,
yangerkun@...wei.com
Subject: [PATCH 6.6 22/28] libfs: Re-arrange locking in offset_iterate_dir()
From: Chuck Lever <chuck.lever@...cle.com>
commit 3f6d810665dfde0d33785420618ceb03fba0619d upstream.
Liam and Matthew say that once the RCU read lock is released,
xa_state is not safe to re-use for the next xas_find() call. But the
RCU read lock must be released on each loop iteration so that
dput(), which might_sleep(), can be called safely.
Thus we are forced to walk the offset tree with fresh state for each
directory entry. xa_find() can do this for us, though it might be a
little less efficient than maintaining xa_state locally.
We believe that in the current code base, inode->i_rwsem provides
protection for the xa_state maintained in
offset_iterate_dir(). However, there is no guarantee that will
continue to be the case in the future.
Since offset_iterate_dir() doesn't build xa_state locally any more,
there's no longer a strong need for offset_find_next(). Clean up by
rolling these two helpers together.
Suggested-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Message-ID: <170785993027.11135.8830043889278631735.stgit@...116.238.104.host.secureserver.net>
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Link: https://lore.kernel.org/r/170820142021.6328.15047865406275957018.stgit@91.116.238.104.host.secureserver.net
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
fs/libfs.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index dc0f7519045f..430f7c95336c 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -401,12 +401,13 @@ static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
return vfs_setpos(file, offset, U32_MAX);
}
-static struct dentry *offset_find_next(struct xa_state *xas)
+static struct dentry *offset_find_next(struct offset_ctx *octx, loff_t offset)
{
struct dentry *child, *found = NULL;
+ XA_STATE(xas, &octx->xa, offset);
rcu_read_lock();
- child = xas_next_entry(xas, U32_MAX);
+ child = xas_next_entry(&xas, U32_MAX);
if (!child)
goto out;
spin_lock(&child->d_lock);
@@ -429,12 +430,11 @@ static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
{
- struct offset_ctx *so_ctx = inode->i_op->get_offset_ctx(inode);
- XA_STATE(xas, &so_ctx->xa, ctx->pos);
+ struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode);
struct dentry *dentry;
while (true) {
- dentry = offset_find_next(&xas);
+ dentry = offset_find_next(octx, ctx->pos);
if (!dentry)
return ERR_PTR(-ENOENT);
@@ -443,8 +443,8 @@ static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
break;
}
+ ctx->pos = dentry2offset(dentry) + 1;
dput(dentry);
- ctx->pos = xas.xa_index + 1;
}
return NULL;
}
--
2.39.2
Powered by blists - more mailing lists