From: Vadim Lobanov Date: Sun, 10 Dec 2006 10:21:17 +0000 (-0800) Subject: [PATCH] fdtable: Remove the free_files field X-Git-Tag: v2.6.20-rc1~145^2~13 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4fd45812cbe875a620c86a096a5d46c742694b7e;p=linux-2.6 [PATCH] fdtable: Remove the free_files field An fdtable can either be embedded inside a files_struct or standalone (after being expanded). When an fdtable is being discarded after all RCU references to it have expired, we must either free it directly, in the standalone case, or free the files_struct it is contained within, in the embedded case. Currently the free_files field controls this behavior, but we can get rid of it entirely, as all the necessary information is already recorded. We can distinguish embedded and standalone fdtables using max_fds, and if it is embedded we can divine the relevant files_struct using container_of(). Signed-off-by: Vadim Lobanov Cc: Christoph Hellwig Cc: Al Viro Cc: Dipankar Sarma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/file.c b/fs/file.c index fb3d2038dc..17e6a55521 100644 --- a/fs/file.c +++ b/fs/file.c @@ -91,7 +91,7 @@ static void free_fdtable_work(struct work_struct *work) } } -static void free_fdtable_rcu(struct rcu_head *rcu) +void free_fdtable_rcu(struct rcu_head *rcu) { struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); int fdset_size, fdarray_size; @@ -101,20 +101,15 @@ static void free_fdtable_rcu(struct rcu_head *rcu) fdset_size = fdt->max_fds / 8; fdarray_size = fdt->max_fds * sizeof(struct file *); - if (fdt->free_files) { + if (fdt->max_fds <= NR_OPEN_DEFAULT) { /* - * The this fdtable was embedded in the files structure - * and the files structure itself was getting destroyed. - * It is now safe to free the files structure. + * This fdtable is embedded in the files structure and that + * structure itself is getting destroyed. */ - kmem_cache_free(files_cachep, fdt->free_files); + kmem_cache_free(files_cachep, + container_of(fdt, struct files_struct, fdtab)); return; } - if (fdt->max_fds <= NR_OPEN_DEFAULT) - /* - * The fdtable was embedded - */ - return; if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) { kfree(fdt->open_fds); kfree(fdt->close_on_exec); @@ -132,12 +127,6 @@ static void free_fdtable_rcu(struct rcu_head *rcu) } } -void free_fdtable(struct fdtable *fdt) -{ - if (fdt->free_files || fdt->max_fds > NR_OPEN_DEFAULT) - call_rcu(&fdt->rcu, free_fdtable_rcu); -} - /* * Expand the fdset in the files_struct. Called with the files spinlock * held for write. @@ -247,7 +236,6 @@ static struct fdtable *alloc_fdtable(int nr) goto out; fdt->fd = new_fds; fdt->max_fds = nfds; - fdt->free_files = NULL; return fdt; out: free_fdset(new_openset, nfds); @@ -283,7 +271,8 @@ static int expand_fdtable(struct files_struct *files, int nr) /* Continue as planned */ copy_fdtable(new_fdt, cur_fdt); rcu_assign_pointer(files->fdt, new_fdt); - free_fdtable(cur_fdt); + if (cur_fdt->max_fds > NR_OPEN_DEFAULT) + call_rcu(&cur_fdt->rcu, free_fdtable_rcu); } else { /* Somebody else expanded, so undo our attempt */ __free_fdtable(new_fdt); diff --git a/include/linux/file.h b/include/linux/file.h index 02be401222..319118f275 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -32,7 +32,6 @@ struct fdtable { fd_set *close_on_exec; fd_set *open_fds; struct rcu_head rcu; - struct files_struct *free_files; struct fdtable *next; }; @@ -84,7 +83,7 @@ extern fd_set *alloc_fdset(int); extern void free_fdset(fd_set *, int); extern int expand_files(struct files_struct *, int nr); -extern void free_fdtable(struct fdtable *fdt); +extern void free_fdtable_rcu(struct rcu_head *rcu); extern void __init files_defer_init(void); static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd) diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 58c18daab6..b531515019 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -16,7 +16,6 @@ .close_on_exec = (fd_set *)&init_files.close_on_exec_init, \ .open_fds = (fd_set *)&init_files.open_fds_init, \ .rcu = RCU_HEAD_INIT, \ - .free_files = NULL, \ .next = NULL, \ } diff --git a/kernel/exit.c b/kernel/exit.c index 5f77e76b4f..122fadb972 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -466,11 +466,9 @@ void fastcall put_files_struct(struct files_struct *files) * you can free files immediately. */ fdt = files_fdtable(files); - if (fdt == &files->fdtab) - fdt->free_files = files; - else + if (fdt != &files->fdtab) kmem_cache_free(files_cachep, files); - free_fdtable(fdt); + call_rcu(&fdt->rcu, free_fdtable_rcu); } } diff --git a/kernel/fork.c b/kernel/fork.c index aba595424f..d16c566eb6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -645,7 +645,6 @@ static struct files_struct *alloc_files(void) fdt->open_fds = (fd_set *)&newf->open_fds_init; fdt->fd = &newf->fd_array[0]; INIT_RCU_HEAD(&fdt->rcu); - fdt->free_files = NULL; fdt->next = NULL; rcu_assign_pointer(newf->fdt, fdt); out: