On Wed, Mar 25, 2026 at 11:32 AM Mike Rapoport <[email protected]> wrote: > > On Mon, Mar 23, 2026 at 08:31:44PM +0000, Pasha Tatashin wrote: > > Currently, LUO does not prevent the same file from being managed twice > > across different active sessions. > > > > Use a global xarray `luo_preserved_files_xa` to keep track of file > > Do we really need _xa suffix?
I liked it, because `luo_preserved_files` is a little too plain, and not self-descriptive. Anyways, I can change it. Pasha > > > pointers being preserved by LUO. Update luo_preserve_file() to check and > > insert the file pointer into this xarray when it is preserved, and > > erase it in luo_file_unpreserve_files() when it is released. > > > > This ensures that the same file (struct file) cannot be managed by > > multiple sessions. If another session attempts to preserve an already > > managed file, it will now fail with -EBUSY. > > > > Signed-off-by: Pasha Tatashin <[email protected]> > > --- > > kernel/liveupdate/luo_file.c | 17 +++++++++++++++-- > > 1 file changed, 15 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c > > index a38ea4975824..5f48c3c8c561 100644 > > --- a/kernel/liveupdate/luo_file.c > > +++ b/kernel/liveupdate/luo_file.c > > @@ -110,11 +110,15 @@ > > #include <linux/sizes.h> > > #include <linux/slab.h> > > #include <linux/string.h> > > +#include <linux/xarray.h> > > #include "luo_internal.h" > > > > static DECLARE_RWSEM(luo_file_handler_lock); > > static LIST_HEAD(luo_file_handler_list); > > > > +/* Keep track of files being preserved by LUO */ > > +static DEFINE_XARRAY(luo_preserved_files_xa); > > + > > /* 2 4K pages, give space for 128 files per file_set */ > > #define LUO_FILE_PGCNT 2ul > > #define LUO_FILE_MAX \ > > @@ -249,6 +253,7 @@ static bool luo_token_is_used(struct luo_file_set > > *file_set, u64 token) > > * Context: Can be called from an ioctl handler during normal system > > operation. > > * Return: 0 on success. Returns a negative errno on failure: > > * -EEXIST if the token is already used. > > + * -EBUSY if the file descriptor is already preserved by another > > session. > > * -EBADF if the file descriptor is invalid. > > * -ENOSPC if the file_set is full. > > * -ENOENT if no compatible handler is found. > > @@ -277,6 +282,11 @@ int luo_preserve_file(struct luo_file_set *file_set, > > u64 token, int fd) > > if (err) > > goto err_fput; > > > > + err = xa_insert(&luo_preserved_files_xa, (unsigned long)file, > > + file, GFP_KERNEL); > > + if (err) > > + goto err_free_files_mem; > > + > > err = -ENOENT; > > scoped_guard(rwsem_read, &luo_file_handler_lock) { > > list_private_for_each_entry(fh, &luo_file_handler_list, list) > > { > > @@ -289,11 +299,11 @@ int luo_preserve_file(struct luo_file_set *file_set, > > u64 token, int fd) > > > > /* err is still -ENOENT if no handler was found */ > > if (err) > > - goto err_free_files_mem; > > + goto err_erase_xa; > > > > err = luo_flb_file_preserve(fh); > > if (err) > > - goto err_free_files_mem; > > + goto err_erase_xa; > > > > luo_file = kzalloc_obj(*luo_file); > > if (!luo_file) { > > @@ -323,6 +333,8 @@ int luo_preserve_file(struct luo_file_set *file_set, > > u64 token, int fd) > > kfree(luo_file); > > err_flb_unpreserve: > > luo_flb_file_unpreserve(fh); > > +err_erase_xa: > > + xa_erase(&luo_preserved_files_xa, (unsigned long)file); > > err_free_files_mem: > > luo_free_files_mem(file_set); > > err_fput: > > @@ -366,6 +378,7 @@ void luo_file_unpreserve_files(struct luo_file_set > > *file_set) > > luo_file->fh->ops->unpreserve(&args); > > luo_flb_file_unpreserve(luo_file->fh); > > > > + xa_erase(&luo_preserved_files_xa, (unsigned > > long)luo_file->file); > > list_del(&luo_file->list); > > file_set->count--; > > > > -- > > 2.43.0 > > > > -- > Sincerely yours, > Mike.
