From 1dce27c5aa6770e9d195f2bb7db1db3d4dde5591 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 16 Feb 2012 17:49:42 +0000 Subject: Wrap accesses to the fd_sets in struct fdtable Wrap accesses to the fd_sets in struct fdtable (for recording open files and close-on-exec flags) so that we can move away from using fd_sets since we abuse the fd_set structs by not allocating the full-sized structure under normal circumstances and by non-core code looking at the internals of the fd_sets. The first abuse means that use of FD_ZERO() on these fd_sets is not permitted, since that cannot be told about their abnormal lengths. This introduces six wrapper functions for setting, clearing and testing close-on-exec flags and fd-is-open flags: void __set_close_on_exec(int fd, struct fdtable *fdt); void __clear_close_on_exec(int fd, struct fdtable *fdt); bool close_on_exec(int fd, const struct fdtable *fdt); void __set_open_fd(int fd, struct fdtable *fdt); void __clear_open_fd(int fd, struct fdtable *fdt); bool fd_is_open(int fd, const struct fdtable *fdt); Note that I've prepended '__' to the names of the set/clear functions because they require the caller to hold a lock to use them. Note also that I haven't added wrappers for looking behind the scenes at the the array. Possibly that should exist too. Signed-off-by: David Howells Link: http://lkml.kernel.org/r/20120216174942.23314.1364.stgit@warthog.procyon.org.uk Signed-off-by: H. Peter Anvin Cc: Al Viro --- include/linux/fdtable.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'include/linux/fdtable.h') diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 82163c4b32c9..7675da2c18f7 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -38,6 +38,36 @@ struct fdtable { struct fdtable *next; }; +static inline void __set_close_on_exec(int fd, struct fdtable *fdt) +{ + FD_SET(fd, fdt->close_on_exec); +} + +static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) +{ + FD_CLR(fd, fdt->close_on_exec); +} + +static inline bool close_on_exec(int fd, const struct fdtable *fdt) +{ + return FD_ISSET(fd, fdt->close_on_exec); +} + +static inline void __set_open_fd(int fd, struct fdtable *fdt) +{ + FD_SET(fd, fdt->open_fds); +} + +static inline void __clear_open_fd(int fd, struct fdtable *fdt) +{ + FD_CLR(fd, fdt->open_fds); +} + +static inline bool fd_is_open(int fd, const struct fdtable *fdt) +{ + return FD_ISSET(fd, fdt->open_fds); +} + /* * Open file table structure */ -- cgit v1.2.3 From 1fd36adcd98c14d2fd97f545293c488775cb2823 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 16 Feb 2012 17:49:54 +0000 Subject: Replace the fd_sets in struct fdtable with an array of unsigned longs Replace the fd_sets in struct fdtable with an array of unsigned longs and then use the standard non-atomic bit operations rather than the FD_* macros. This: (1) Removes the abuses of struct fd_set: (a) Since we don't want to allocate a full fd_set the vast majority of the time, we actually, in effect, just allocate a just-big-enough array of unsigned longs and cast it to an fd_set type - so why bother with the fd_set at all? (b) Some places outside of the core fdtable handling code (such as SELinux) want to look inside the array of unsigned longs hidden inside the fd_set struct for more efficient iteration over the entire set. (2) Eliminates the use of FD_*() macros in the kernel completely. (3) Permits the __FD_*() macros to be deleted entirely where not exposed to userspace. Signed-off-by: David Howells Link: http://lkml.kernel.org/r/20120216174954.23314.48147.stgit@warthog.procyon.org.uk Signed-off-by: H. Peter Anvin Cc: Al Viro --- include/linux/fdtable.h | 28 ++++++++++------------------ 1 file changed, 10 insertions(+), 18 deletions(-) (limited to 'include/linux/fdtable.h') diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 7675da2c18f7..158a41eed314 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -21,51 +21,43 @@ */ #define NR_OPEN_DEFAULT BITS_PER_LONG -/* - * The embedded_fd_set is a small fd_set, - * suitable for most tasks (which open <= BITS_PER_LONG files) - */ -struct embedded_fd_set { - unsigned long fds_bits[1]; -}; - struct fdtable { unsigned int max_fds; struct file __rcu **fd; /* current fd array */ - fd_set *close_on_exec; - fd_set *open_fds; + unsigned long *close_on_exec; + unsigned long *open_fds; struct rcu_head rcu; struct fdtable *next; }; static inline void __set_close_on_exec(int fd, struct fdtable *fdt) { - FD_SET(fd, fdt->close_on_exec); + __set_bit(fd, fdt->close_on_exec); } static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) { - FD_CLR(fd, fdt->close_on_exec); + __clear_bit(fd, fdt->close_on_exec); } static inline bool close_on_exec(int fd, const struct fdtable *fdt) { - return FD_ISSET(fd, fdt->close_on_exec); + return test_bit(fd, fdt->close_on_exec); } static inline void __set_open_fd(int fd, struct fdtable *fdt) { - FD_SET(fd, fdt->open_fds); + __set_bit(fd, fdt->open_fds); } static inline void __clear_open_fd(int fd, struct fdtable *fdt) { - FD_CLR(fd, fdt->open_fds); + __clear_bit(fd, fdt->open_fds); } static inline bool fd_is_open(int fd, const struct fdtable *fdt) { - return FD_ISSET(fd, fdt->open_fds); + return test_bit(fd, fdt->open_fds); } /* @@ -83,8 +75,8 @@ struct files_struct { */ spinlock_t file_lock ____cacheline_aligned_in_smp; int next_fd; - struct embedded_fd_set close_on_exec_init; - struct embedded_fd_set open_fds_init; + unsigned long close_on_exec_init[1]; + unsigned long open_fds_init[1]; struct file __rcu * fd_array[NR_OPEN_DEFAULT]; }; -- cgit v1.2.3