From 7d8a45695cc8f9fcdf4121fcbd897ecb63f758e4 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 7 Jun 2012 14:21:13 -0700 Subject: [PATCH] ipc: shm: restore MADV_REMOVE functionality on shared memory segments Commit 17cf28afea2a ("mm/fs: remove truncate_range") removed the truncate_range inode operation in favour of the fallocate file operation. When using SYSV IPC shared memory segments, calling madvise with the MADV_REMOVE advice on an area of shared memory will attempt to invoke the .fallocate function for the shm_file_operations, which is NULL and therefore returns -EOPNOTSUPP to userspace. The previous behaviour would inherit the inode_operations from the underlying tmpfs file and invoke truncate_range there. This patch restores the previous behaviour by wrapping the underlying fallocate function in shm_fallocate, as we do for fsync. [hughd@google.com: use -ENOTSUPP in shm_fallocate()] Signed-off-by: Will Deacon Acked-by: Hugh Dickins Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/shm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/ipc/shm.c b/ipc/shm.c index 5e2cbfdab6fc..41c1285d697a 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -393,6 +393,16 @@ static int shm_fsync(struct file *file, loff_t start, loff_t end, int datasync) return sfd->file->f_op->fsync(sfd->file, start, end, datasync); } +static long shm_fallocate(struct file *file, int mode, loff_t offset, + loff_t len) +{ + struct shm_file_data *sfd = shm_file_data(file); + + if (!sfd->file->f_op->fallocate) + return -EOPNOTSUPP; + return sfd->file->f_op->fallocate(file, mode, offset, len); +} + static unsigned long shm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) @@ -410,6 +420,7 @@ static const struct file_operations shm_file_operations = { .get_unmapped_area = shm_get_unmapped_area, #endif .llseek = noop_llseek, + .fallocate = shm_fallocate, }; static const struct file_operations shm_file_operations_huge = { @@ -418,6 +429,7 @@ static const struct file_operations shm_file_operations_huge = { .release = shm_release, .get_unmapped_area = shm_get_unmapped_area, .llseek = noop_llseek, + .fallocate = shm_fallocate, }; int is_file_shm_hugepages(struct file *file) -- 2.30.2