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author | Dipankar Sarma <dipankar@in.ibm.com> | 2005-09-09 13:04:13 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-09 13:57:55 -0700 |
commit | ab2af1f5005069321c5d130f09cce577b03f43ef (patch) | |
tree | 73a70ba486f522cd9eeeef376ede2b5a1c1b473b /include/linux | |
parent | 6e72ad2c581de121cc7e772469e2a8f6b1fd4379 (diff) | |
download | linux-stable-ab2af1f5005069321c5d130f09cce577b03f43ef.tar.gz linux-stable-ab2af1f5005069321c5d130f09cce577b03f43ef.tar.bz2 linux-stable-ab2af1f5005069321c5d130f09cce577b03f43ef.zip |
[PATCH] files: files struct with RCU
Patch to eliminate struct files_struct.file_lock spinlock on the reader side
and use rcu refcounting rcuref_xxx api for the f_count refcounter. The
updates to the fdtable are done by allocating a new fdtable structure and
setting files->fdt to point to the new structure. The fdtable structure is
protected by RCU thereby allowing lock-free lookup. For fd arrays/sets that
are vmalloced, we use keventd to free them since RCU callbacks can't sleep. A
global list of fdtable to be freed is not scalable, so we use a per-cpu list.
If keventd is already handling the current cpu's work, we use a timer to defer
queueing of that work.
Since the last publication, this patch has been re-written to avoid using
explicit memory barriers and use rcu_assign_pointer(), rcu_dereference()
premitives instead. This required that the fd information is kept in a
separate structure (fdtable) and updated atomically.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/file.h | 11 | ||||
-rw-r--r-- | include/linux/fs.h | 4 | ||||
-rw-r--r-- | include/linux/init_task.h | 5 |
3 files changed, 17 insertions, 3 deletions
diff --git a/include/linux/file.h b/include/linux/file.h index db372230848e..f5bbd4c508b3 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -9,6 +9,7 @@ #include <linux/posix_types.h> #include <linux/compiler.h> #include <linux/spinlock.h> +#include <linux/rcupdate.h> /* * The default fd array needs to be at least BITS_PER_LONG, @@ -23,6 +24,9 @@ struct fdtable { struct file ** fd; /* current fd array */ fd_set *close_on_exec; fd_set *open_fds; + struct rcu_head rcu; + struct files_struct *free_files; + struct fdtable *next; }; /* @@ -31,13 +35,14 @@ struct fdtable { struct files_struct { atomic_t count; spinlock_t file_lock; /* Protects all the below members. Nests inside tsk->alloc_lock */ + struct fdtable *fdt; struct fdtable fdtab; fd_set close_on_exec_init; fd_set open_fds_init; struct file * fd_array[NR_OPEN_DEFAULT]; }; -#define files_fdtable(files) (&(files)->fdtab) +#define files_fdtable(files) (rcu_dereference((files)->fdt)) extern void FASTCALL(__fput(struct file *)); extern void FASTCALL(fput(struct file *)); @@ -65,6 +70,8 @@ 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 __init files_defer_init(void); static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd) { @@ -72,7 +79,7 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in struct fdtable *fdt = files_fdtable(files); if (fd < fdt->max_fds) - file = fdt->fd[fd]; + file = rcu_dereference(fdt->fd[fd]); return file; } diff --git a/include/linux/fs.h b/include/linux/fs.h index fd93ab7da905..7f61227827d7 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -9,6 +9,7 @@ #include <linux/config.h> #include <linux/limits.h> #include <linux/ioctl.h> +#include <linux/rcuref.h> /* * It's silly to have NR_OPEN bigger than NR_FILE, but you can change @@ -597,12 +598,13 @@ struct file { spinlock_t f_ep_lock; #endif /* #ifdef CONFIG_EPOLL */ struct address_space *f_mapping; + struct rcu_head f_rcuhead; }; extern spinlock_t files_lock; #define file_list_lock() spin_lock(&files_lock); #define file_list_unlock() spin_unlock(&files_lock); -#define get_file(x) atomic_inc(&(x)->f_count) +#define get_file(x) rcuref_inc(&(x)->f_count) #define file_count(x) atomic_read(&(x)->f_count) #define MAX_NON_LFS ((1UL<<31) - 1) diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 94aefa54a1b5..68ab5f2ab9cd 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -2,6 +2,7 @@ #define _LINUX__INIT_TASK_H #include <linux/file.h> +#include <linux/rcupdate.h> #define INIT_FDTABLE \ { \ @@ -11,12 +12,16 @@ .fd = &init_files.fd_array[0], \ .close_on_exec = &init_files.close_on_exec_init, \ .open_fds = &init_files.open_fds_init, \ + .rcu = RCU_HEAD_INIT, \ + .free_files = NULL, \ + .next = NULL, \ } #define INIT_FILES \ { \ .count = ATOMIC_INIT(1), \ .file_lock = SPIN_LOCK_UNLOCKED, \ + .fdt = &init_files.fdtab, \ .fdtab = INIT_FDTABLE, \ .close_on_exec_init = { { 0, } }, \ .open_fds_init = { { 0, } }, \ |