From 1fd36adcd98c14d2fd97f545293c488775cb2823 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 16 Feb 2012 17:49:54 +0000 Subject: [PATCH] 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 --- fs/exec.c | 4 ++-- fs/file.c | 46 +++++++++++++++++++--------------------- fs/select.c | 2 +- include/linux/fdtable.h | 28 +++++++++--------------- kernel/exit.c | 2 +- security/selinux/hooks.c | 2 +- 6 files changed, 37 insertions(+), 47 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 22cc38d9e79f..cfd5e3047bd8 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1026,10 +1026,10 @@ static void flush_old_files(struct files_struct * files) fdt = files_fdtable(files); if (i >= fdt->max_fds) break; - set = fdt->close_on_exec->fds_bits[j]; + set = fdt->close_on_exec[j]; if (!set) continue; - fdt->close_on_exec->fds_bits[j] = 0; + fdt->close_on_exec[j] = 0; spin_unlock(&files->file_lock); for ( ; set ; i++,set >>= 1) { if (set & 1) { diff --git a/fs/file.c b/fs/file.c index 114fea0a2cec..2d479dd8484e 100644 --- a/fs/file.c +++ b/fs/file.c @@ -40,7 +40,7 @@ int sysctl_nr_open_max = 1024 * 1024; /* raised later */ */ static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); -static void *alloc_fdmem(unsigned int size) +static void *alloc_fdmem(size_t size) { /* * Very large allocations can stress page reclaim, so fall back to @@ -142,7 +142,7 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) static struct fdtable * alloc_fdtable(unsigned int nr) { struct fdtable *fdt; - char *data; + void *data; /* * Figure out how many fds we actually want to support in this fdtable. @@ -172,14 +172,15 @@ static struct fdtable * alloc_fdtable(unsigned int nr) data = alloc_fdmem(nr * sizeof(struct file *)); if (!data) goto out_fdt; - fdt->fd = (struct file **)data; - data = alloc_fdmem(max_t(unsigned int, + fdt->fd = data; + + data = alloc_fdmem(max_t(size_t, 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); if (!data) goto out_arr; - fdt->open_fds = (fd_set *)data; - data += nr / BITS_PER_BYTE; - fdt->close_on_exec = (fd_set *)data; + fdt->open_fds = data; + data += nr / BITS_PER_LONG; + fdt->close_on_exec = data; fdt->next = NULL; return fdt; @@ -275,11 +276,11 @@ static int count_open_files(struct fdtable *fdt) int i; /* Find the last open fd */ - for (i = size/(8*sizeof(long)); i > 0; ) { - if (fdt->open_fds->fds_bits[--i]) + for (i = size / BITS_PER_LONG; i > 0; ) { + if (fdt->open_fds[--i]) break; } - i = (i+1) * 8 * sizeof(long); + i = (i + 1) * BITS_PER_LONG; return i; } @@ -306,8 +307,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) newf->next_fd = 0; new_fdt = &newf->fdtab; new_fdt->max_fds = NR_OPEN_DEFAULT; - new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; - new_fdt->open_fds = (fd_set *)&newf->open_fds_init; + new_fdt->close_on_exec = newf->close_on_exec_init; + new_fdt->open_fds = newf->open_fds_init; new_fdt->fd = &newf->fd_array[0]; new_fdt->next = NULL; @@ -350,10 +351,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) old_fds = old_fdt->fd; new_fds = new_fdt->fd; - memcpy(new_fdt->open_fds->fds_bits, - old_fdt->open_fds->fds_bits, open_files/8); - memcpy(new_fdt->close_on_exec->fds_bits, - old_fdt->close_on_exec->fds_bits, open_files/8); + memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); + memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); for (i = open_files; i != 0; i--) { struct file *f = *old_fds++; @@ -379,11 +378,11 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) memset(new_fds, 0, size); if (new_fdt->max_fds > open_files) { - int left = (new_fdt->max_fds-open_files)/8; - int start = open_files / (8 * sizeof(unsigned long)); + int left = (new_fdt->max_fds - open_files) / 8; + int start = open_files / BITS_PER_LONG; - memset(&new_fdt->open_fds->fds_bits[start], 0, left); - memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); + memset(&new_fdt->open_fds[start], 0, left); + memset(&new_fdt->close_on_exec[start], 0, left); } rcu_assign_pointer(newf->fdt, new_fdt); @@ -419,8 +418,8 @@ struct files_struct init_files = { .fdtab = { .max_fds = NR_OPEN_DEFAULT, .fd = &init_files.fd_array[0], - .close_on_exec = (fd_set *)&init_files.close_on_exec_init, - .open_fds = (fd_set *)&init_files.open_fds_init, + .close_on_exec = init_files.close_on_exec_init, + .open_fds = init_files.open_fds_init, }, .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock), }; @@ -443,8 +442,7 @@ repeat: fd = files->next_fd; if (fd < fdt->max_fds) - fd = find_next_zero_bit(fdt->open_fds->fds_bits, - fdt->max_fds, fd); + fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); error = expand_files(files, fd); if (error < 0) diff --git a/fs/select.c b/fs/select.c index d33418fdc858..2e7fbe8a092c 100644 --- a/fs/select.c +++ b/fs/select.c @@ -348,7 +348,7 @@ static int max_select_fd(unsigned long n, fd_set_bits *fds) set = ~(~0UL << (n & (__NFDBITS-1))); n /= __NFDBITS; fdt = files_fdtable(current->files); - open_fds = fdt->open_fds->fds_bits+n; + open_fds = fdt->open_fds + n; max = 0; if (set) { set &= BITS(fds, n); 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]; }; diff --git a/kernel/exit.c b/kernel/exit.c index 4b4042f9bc6a..4db020015f14 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -473,7 +473,7 @@ static void close_files(struct files_struct * files) i = j * __NFDBITS; if (i >= fdt->max_fds) break; - set = fdt->open_fds->fds_bits[j++]; + set = fdt->open_fds[j++]; while (set) { if (set & 1) { struct file * file = xchg(&fdt->fd[i], NULL); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 6a3683e28426..421c990a20b2 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2145,7 +2145,7 @@ static inline void flush_unauthorized_files(const struct cred *cred, fdt = files_fdtable(files); if (i >= fdt->max_fds) break; - set = fdt->open_fds->fds_bits[j]; + set = fdt->open_fds[j]; if (!set) continue; spin_unlock(&files->file_lock); -- 2.34.1