Commit 4fd45812cbe875a620c86a096a5d46c742694b7e
Committed by
Linus Torvalds
Linus Torvalds
1 parent
bbea9f6966
Exists in
master
and in
4 other branches
[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 <vlobanov@speakeasy.net> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Showing 5 changed files with 11 additions and 27 deletions Side-by-side Diff
fs/file.c
| ... | ... | @@ -91,7 +91,7 @@ |
| 91 | 91 | } |
| 92 | 92 | } |
| 93 | 93 | |
| 94 | -static void free_fdtable_rcu(struct rcu_head *rcu) | |
| 94 | +void free_fdtable_rcu(struct rcu_head *rcu) | |
| 95 | 95 | { |
| 96 | 96 | struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); |
| 97 | 97 | int fdset_size, fdarray_size; |
| 98 | 98 | |
| 99 | 99 | |
| 100 | 100 | |
| ... | ... | @@ -101,20 +101,15 @@ |
| 101 | 101 | fdset_size = fdt->max_fds / 8; |
| 102 | 102 | fdarray_size = fdt->max_fds * sizeof(struct file *); |
| 103 | 103 | |
| 104 | - if (fdt->free_files) { | |
| 104 | + if (fdt->max_fds <= NR_OPEN_DEFAULT) { | |
| 105 | 105 | /* |
| 106 | - * The this fdtable was embedded in the files structure | |
| 107 | - * and the files structure itself was getting destroyed. | |
| 108 | - * It is now safe to free the files structure. | |
| 106 | + * This fdtable is embedded in the files structure and that | |
| 107 | + * structure itself is getting destroyed. | |
| 109 | 108 | */ |
| 110 | - kmem_cache_free(files_cachep, fdt->free_files); | |
| 109 | + kmem_cache_free(files_cachep, | |
| 110 | + container_of(fdt, struct files_struct, fdtab)); | |
| 111 | 111 | return; |
| 112 | 112 | } |
| 113 | - if (fdt->max_fds <= NR_OPEN_DEFAULT) | |
| 114 | - /* | |
| 115 | - * The fdtable was embedded | |
| 116 | - */ | |
| 117 | - return; | |
| 118 | 113 | if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) { |
| 119 | 114 | kfree(fdt->open_fds); |
| 120 | 115 | kfree(fdt->close_on_exec); |
| ... | ... | @@ -132,12 +127,6 @@ |
| 132 | 127 | } |
| 133 | 128 | } |
| 134 | 129 | |
| 135 | -void free_fdtable(struct fdtable *fdt) | |
| 136 | -{ | |
| 137 | - if (fdt->free_files || fdt->max_fds > NR_OPEN_DEFAULT) | |
| 138 | - call_rcu(&fdt->rcu, free_fdtable_rcu); | |
| 139 | -} | |
| 140 | - | |
| 141 | 130 | /* |
| 142 | 131 | * Expand the fdset in the files_struct. Called with the files spinlock |
| 143 | 132 | * held for write. |
| ... | ... | @@ -247,7 +236,6 @@ |
| 247 | 236 | goto out; |
| 248 | 237 | fdt->fd = new_fds; |
| 249 | 238 | fdt->max_fds = nfds; |
| 250 | - fdt->free_files = NULL; | |
| 251 | 239 | return fdt; |
| 252 | 240 | out: |
| 253 | 241 | free_fdset(new_openset, nfds); |
| ... | ... | @@ -283,7 +271,8 @@ |
| 283 | 271 | /* Continue as planned */ |
| 284 | 272 | copy_fdtable(new_fdt, cur_fdt); |
| 285 | 273 | rcu_assign_pointer(files->fdt, new_fdt); |
| 286 | - free_fdtable(cur_fdt); | |
| 274 | + if (cur_fdt->max_fds > NR_OPEN_DEFAULT) | |
| 275 | + call_rcu(&cur_fdt->rcu, free_fdtable_rcu); | |
| 287 | 276 | } else { |
| 288 | 277 | /* Somebody else expanded, so undo our attempt */ |
| 289 | 278 | __free_fdtable(new_fdt); |
include/linux/file.h
| ... | ... | @@ -32,7 +32,6 @@ |
| 32 | 32 | fd_set *close_on_exec; |
| 33 | 33 | fd_set *open_fds; |
| 34 | 34 | struct rcu_head rcu; |
| 35 | - struct files_struct *free_files; | |
| 36 | 35 | struct fdtable *next; |
| 37 | 36 | }; |
| 38 | 37 | |
| ... | ... | @@ -84,7 +83,7 @@ |
| 84 | 83 | extern void free_fdset(fd_set *, int); |
| 85 | 84 | |
| 86 | 85 | extern int expand_files(struct files_struct *, int nr); |
| 87 | -extern void free_fdtable(struct fdtable *fdt); | |
| 86 | +extern void free_fdtable_rcu(struct rcu_head *rcu); | |
| 88 | 87 | extern void __init files_defer_init(void); |
| 89 | 88 | |
| 90 | 89 | static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd) |
include/linux/init_task.h
kernel/exit.c
| ... | ... | @@ -466,11 +466,9 @@ |
| 466 | 466 | * you can free files immediately. |
| 467 | 467 | */ |
| 468 | 468 | fdt = files_fdtable(files); |
| 469 | - if (fdt == &files->fdtab) | |
| 470 | - fdt->free_files = files; | |
| 471 | - else | |
| 469 | + if (fdt != &files->fdtab) | |
| 472 | 470 | kmem_cache_free(files_cachep, files); |
| 473 | - free_fdtable(fdt); | |
| 471 | + call_rcu(&fdt->rcu, free_fdtable_rcu); | |
| 474 | 472 | } |
| 475 | 473 | } |
| 476 | 474 |
kernel/fork.c