6.12-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
[ Upstream commit e1b4c6a58304fd490124cc2b454d80edc786665c ]
maple_tree insertions can fail if we are seriously short on memory; simple_offset_rename() does not recover well if it runs into that. The same goes for simple_offset_rename_exchange().
Moreover, shmem_whiteout() expects that if it succeeds, the caller will progress to d_move(), i.e. that shmem_rename2() won't fail past the successful call of shmem_whiteout().
Not hard to fix, fortunately - mtree_store() can't fail if the index we are trying to store into is already present in the tree as a singleton.
For simple_offset_rename_exchange() that's enough - we just need to be careful about the order of operations.
For simple_offset_rename() solution is to preinsert the target into the tree for new_dir; the rest can be done without any potentially failing operations.
That preinsertion has to be done in shmem_rename2() rather than in simple_offset_rename() itself - otherwise we'd need to deal with the possibility of failure after successful shmem_whiteout().
Fixes: a2e459555c5f ("shmem: stable directory offsets") Reviewed-by: Christian Brauner brauner@kernel.org Reviewed-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/libfs.c | 50 +++++++++++++++++++--------------------------- include/linux/fs.h | 2 +- mm/shmem.c | 18 ++++++++++++----- 3 files changed, 35 insertions(+), 35 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c index 8743241678496..028f2cf729d5d 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -345,22 +345,22 @@ void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry) * User space expects the directory offset value of the replaced * (new) directory entry to be unchanged after a rename. * - * Returns zero on success, a negative errno value on failure. + * Caller must have grabbed a slot for new_dentry in the maple_tree + * associated with new_dir, even if dentry is negative. */ -int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, - struct inode *new_dir, struct dentry *new_dentry) +void simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) { struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir); struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir); long new_offset = dentry2offset(new_dentry);
- simple_offset_remove(old_ctx, old_dentry); + if (WARN_ON(!new_offset)) + return;
- if (new_offset) { - offset_set(new_dentry, 0); - return simple_offset_replace(new_ctx, old_dentry, new_offset); - } - return simple_offset_add(new_ctx, old_dentry); + simple_offset_remove(old_ctx, old_dentry); + offset_set(new_dentry, 0); + WARN_ON(simple_offset_replace(new_ctx, old_dentry, new_offset)); }
/** @@ -387,31 +387,23 @@ int simple_offset_rename_exchange(struct inode *old_dir, long new_index = dentry2offset(new_dentry); int ret;
- simple_offset_remove(old_ctx, old_dentry); - simple_offset_remove(new_ctx, new_dentry); + if (WARN_ON(!old_index || !new_index)) + return -EINVAL;
- ret = simple_offset_replace(new_ctx, old_dentry, new_index); - if (ret) - goto out_restore; + ret = mtree_store(&new_ctx->mt, new_index, old_dentry, GFP_KERNEL); + if (WARN_ON(ret)) + return ret;
- ret = simple_offset_replace(old_ctx, new_dentry, old_index); - if (ret) { - simple_offset_remove(new_ctx, old_dentry); - goto out_restore; + ret = mtree_store(&old_ctx->mt, old_index, new_dentry, GFP_KERNEL); + if (WARN_ON(ret)) { + mtree_store(&new_ctx->mt, new_index, new_dentry, GFP_KERNEL); + return ret; }
- ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry); - if (ret) { - simple_offset_remove(new_ctx, old_dentry); - simple_offset_remove(old_ctx, new_dentry); - goto out_restore; - } + offset_set(old_dentry, new_index); + offset_set(new_dentry, old_index); + simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry); return 0; - -out_restore: - (void)simple_offset_replace(old_ctx, old_dentry, old_index); - (void)simple_offset_replace(new_ctx, new_dentry, new_index); - return ret; }
/** diff --git a/include/linux/fs.h b/include/linux/fs.h index 37a01c9d96583..87720e1b54192 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3446,7 +3446,7 @@ struct offset_ctx { void simple_offset_init(struct offset_ctx *octx); int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry); void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry); -int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, +void simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry); int simple_offset_rename_exchange(struct inode *old_dir, struct dentry *old_dentry, diff --git a/mm/shmem.c b/mm/shmem.c index 7e07188e82696..0c3113b5b5aaa 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3749,6 +3749,7 @@ static int shmem_rename2(struct mnt_idmap *idmap, { struct inode *inode = d_inode(old_dentry); int they_are_dirs = S_ISDIR(inode->i_mode); + bool had_offset = false; int error;
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) @@ -3761,16 +3762,23 @@ static int shmem_rename2(struct mnt_idmap *idmap, if (!simple_empty(new_dentry)) return -ENOTEMPTY;
+ error = simple_offset_add(shmem_get_offset_ctx(new_dir), new_dentry); + if (error == -EBUSY) + had_offset = true; + else if (unlikely(error)) + return error; + if (flags & RENAME_WHITEOUT) { error = shmem_whiteout(idmap, old_dir, old_dentry); - if (error) + if (error) { + if (!had_offset) + simple_offset_remove(shmem_get_offset_ctx(new_dir), + new_dentry); return error; + } }
- error = simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry); - if (error) - return error; - + simple_offset_rename(old_dir, old_dentry, new_dir, new_dentry); if (d_really_is_positive(new_dentry)) { (void) shmem_unlink(new_dir, new_dentry); if (they_are_dirs) {