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xfs: optimize inline symlinks

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By overallocating the in-core inode fork data buffer and zero
terminating the link target in xfs_init_local_fork we can avoid
the memory allocation in ->follow_link.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2016-04-06 07:53:29 +10:00 • committed by Dave Chinner
parent bfe8804d90
commit 30ee052e12
4 changed files with 49 additions and 15 deletions
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22
fs/xfs/libxfs/xfs_inode_fork.c
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@ -239,19 +239,33 @@ xfs_init_local_fork(
int size)
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
int real_size = 0;
int mem_size = size, real_size = 0;
bool zero_terminate;
/*
* If we are using the local fork to store a symlink body we need to
* zero-terminate it so that we can pass it back to the VFS directly.
* Overallocate the in-memory fork by one for that and add a zero
* to terminate it below.
*/
zero_terminate = S_ISLNK(VFS_I(ip)->i_mode);
if (zero_terminate)
mem_size++;
if (size == 0)
ifp->if_u1.if_data = NULL;
else if (size <= sizeof(ifp->if_u2.if_inline_data))
else if (mem_size <= sizeof(ifp->if_u2.if_inline_data))
ifp->if_u1.if_data = ifp->if_u2.if_inline_data;
else {
real_size = roundup(size, 4);
real_size = roundup(mem_size, 4);
ifp->if_u1.if_data = kmem_alloc(real_size, KM_SLEEP | KM_NOFS);
}
if (size)
if (size) {
memcpy(ifp->if_u1.if_data, data, size);
if (zero_terminate)
ifp->if_u1.if_data[size] = '\0';
}
ifp->if_bytes = size;
ifp->if_real_bytes = real_size;