From badf16621c1f9d1ac753be056fce11b43d6e0be5 Mon Sep 17 00:00:00 2001 From: Dipankar Sarma Date: Fri, 9 Sep 2005 13:04:10 -0700 Subject: [PATCH] files: break up files struct In order for the RCU to work, the file table array, sets and their sizes must be updated atomically. Instead of ensuring this through too many memory barriers, we put the arrays and their sizes in a separate structure. This patch takes the first step of putting the file table elements in a separate structure fdtable that is embedded withing files_struct. It also changes all the users to refer to the file table using files_fdtable() macro. Subsequent applciation of RCU becomes easier after this. Signed-off-by: Dipankar Sarma Signed-Off-By: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/file.h | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) (limited to 'include/linux/file.h') diff --git a/include/linux/file.h b/include/linux/file.h index 5206beb9a80e..db372230848e 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -16,23 +16,29 @@ */ #define NR_OPEN_DEFAULT BITS_PER_LONG +struct fdtable { + unsigned int max_fds; + int max_fdset; + int next_fd; + struct file ** fd; /* current fd array */ + fd_set *close_on_exec; + fd_set *open_fds; +}; + /* * Open file table structure */ struct files_struct { atomic_t count; spinlock_t file_lock; /* Protects all the below members. Nests inside tsk->alloc_lock */ - int max_fds; - int max_fdset; - int next_fd; - struct file ** fd; /* current fd array */ - fd_set *close_on_exec; - fd_set *open_fds; + 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) + extern void FASTCALL(__fput(struct file *)); extern void FASTCALL(fput(struct file *)); @@ -63,9 +69,10 @@ extern int expand_files(struct files_struct *, int nr); static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd) { struct file * file = NULL; + struct fdtable *fdt = files_fdtable(files); - if (fd < files->max_fds) - file = files->fd[fd]; + if (fd < fdt->max_fds) + file = fdt->fd[fd]; return file; } -- cgit v1.2.2 From ab2af1f5005069321c5d130f09cce577b03f43ef Mon Sep 17 00:00:00 2001 From: Dipankar Sarma Date: Fri, 9 Sep 2005 13:04:13 -0700 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/file.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'include/linux/file.h') 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 #include #include +#include /* * 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; } -- cgit v1.2.2