Commit 7d8a4569 authored Jun 07, 2012 by Will Deacon Committed by Linus Torvalds Jun 07, 2012

ipc: shm: restore MADV_REMOVE functionality on shared memory segments



Commit 17cf28af ("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 <will.deacon@arm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4e791c98

ipc/shm.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -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)

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