- 根目录:
- fs
- xfs
- xfs_filestream.c
/*
* Copyright (c) 2006-2007 Silicon Graphics, Inc.
* Copyright (c) 2014 Christoph Hellwig.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_alloc.h"
#include "xfs_mru_cache.h"
#include "xfs_filestream.h"
#include "xfs_trace.h"
struct xfs_fstrm_item {
struct xfs_mru_cache_elem mru;
struct xfs_inode *ip;
xfs_agnumber_t ag; /* AG in use for this directory */
};
enum xfs_fstrm_alloc {
XFS_PICK_USERDATA = 1,
XFS_PICK_LOWSPACE = 2,
};
/*
* Allocation group filestream associations are tracked with per-ag atomic
* counters. These counters allow xfs_filestream_pick_ag() to tell whether a
* particular AG already has active filestreams associated with it. The mount
* point's m_peraglock is used to protect these counters from per-ag array
* re-allocation during a growfs operation. When xfs_growfs_data_private() is
* about to reallocate the array, it calls xfs_filestream_flush() with the
* m_peraglock held in write mode.
*
* Since xfs_mru_cache_flush() guarantees that all the free functions for all
* the cache elements have finished executing before it returns, it's safe for
* the free functions to use the atomic counters without m_peraglock protection.
* This allows the implementation of xfs_fstrm_free_func() to be agnostic about
* whether it was called with the m_peraglock held in read mode, write mode or
* not held at all. The race condition this addresses is the following:
*
* - The work queue scheduler fires and pulls a filestream directory cache
* element off the LRU end of the cache for deletion, then gets pre-empted.
* - A growfs operation grabs the m_peraglock in write mode, flushes all the
* remaining items from the cache and reallocates the mount point's per-ag
* array, resetting all the counters to zero.
* - The work queue thread resumes and calls the free function for the element
* it started cleaning up earlier. In the process it decrements the
* filestreams counter for an AG that now has no references.
*
* With a shrinkfs feature, the above scenario could panic the system.
*
* All other uses of the following macros should be protected by either the
* m_peraglock held in read mode, or the cache's internal locking exposed by the
* interval between a call to xfs_mru_cache_lookup() and a call to
* xfs_mru_cache_done(). In addition, the m_peraglock must be held in read mode
* when new elements are added to the cache.
*
* Combined, these locking rules ensure that no associations will ever exist in
* the cache that reference per-ag array elements that have since been
* reallocated.
*/
int
xfs_filestream_peek_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ret;
pag = xfs_perag_get(mp, agno);
ret = atomic_read(&pag->pagf_fstrms);
xfs_perag_put(pag);
return ret;
}
static int
xfs_filestream_get_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ret;
pag = xfs_perag_get(mp, agno);
ret = atomic_inc_return(&pag->pagf_fstrms);
xfs_perag_put(pag);
return ret;
}
static void
xfs_filestream_put_ag(
xfs_mount_t *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
pag = xfs_perag_get(mp, agno);
atomic_dec(&pag->pagf_fstrms);
xfs_perag_put(pag);
}
static void
xfs_fstrm_free_func(
struct xfs_mru_cache_elem *mru)
{
struct xfs_fstrm_item *item =
container_of(mru, struct xfs_fstrm_item, mru);
xfs_filestream_put_ag(item->ip->i_mount, item->ag);
trace_xfs_filestream_free(item->ip, item->ag);
kmem_free(item);
}
/*
* Scan the AGs starting at startag looking for an AG that isn't in use and has
* at least minlen blocks free.
*/
static int
xfs_filestream_pick_ag(
struct xfs_inode *ip,
xfs_agnumber_t startag,
xfs_agnumber_t *agp,
int flags,
xfs_extlen_t minlen)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_fstrm_item *item;
struct xfs_perag *pag;
xfs_extlen_t longest, free = 0, minfree, maxfree = 0;
xfs_agnumber_t ag, max_ag = NULLAGNUMBER;
int err, trylock, nscan;
ASSERT(S_ISDIR(ip->i_d.di_mode));
/* 2% of an AG's blocks must be free for it to be chosen. */
minfree = mp->m_sb.sb_agblocks / 50;
ag = startag;
*agp = NULLAGNUMBER;
/* For the first pass, don't sleep trying to init the per-AG. */
trylock = XFS_ALLOC_FLAG_TRYLOCK;
for (nscan = 0; 1; nscan++) {
trace_xfs_filestream_scan(ip, ag);
pag = xfs_perag_get(mp, ag);
if (!pag->pagf_init) {
err = xfs_alloc_pagf_init(mp, NULL, ag, trylock);
if (err && !trylock) {
xfs_perag_put(pag);
return err;
}
}
/* Might fail sometimes during the 1st pass with trylock set. */
if (!pag->pagf_init)
goto next_ag;
/* Keep track of the AG with the most free blocks. */
if (pag->pagf_freeblks > maxfree) {
maxfree = pag->pagf_freeblks;
max_ag = ag;
}
/*
* The AG reference count does two things: it enforces mutual
* exclusion when examining the suitability of an AG in this
* loop, and it guards against two filestreams being established
* in the same AG as each other.
*/
if (xfs_filestream_get_ag(mp, ag) > 1) {
xfs_filestream_put_ag(mp, ag);
goto next_ag;
}
longest = xfs_alloc_longest_free_extent(mp, pag,
xfs_alloc_min_freelist(mp, pag));
if (((minlen && longest >= minlen) ||
(!minlen && pag->pagf_freeblks >= minfree)) &&
(!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||
(flags & XFS_PICK_LOWSPACE))) {
/* Break out, retaining the reference on the AG. */
free = pag->pagf_freeblks;
xfs_perag_put(pag);
*agp = ag;
break;
}
/* Drop the reference on this AG, it's not usable. */
xfs_filestream_put_ag(mp, ag);
next_ag:
xfs_perag_put(pag);
/* Move to the next AG, wrapping to AG 0 if necessary. */
if (++ag >= mp->m_sb.sb_agcount)
ag = 0;
/* If a full pass of the AGs hasn't been done yet, continue. */
if (ag != startag)
continue;
/* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */
if (trylock != 0) {
trylock = 0;
continue;
}
/* Finally, if lowspace wasn't set, set it for the 3rd pass. */
if (!(flags & XFS_PICK_LOWSPACE)) {
flags |= XFS_PICK_LOWSPACE;
continue;
}
/*
* Take the AG with the most free space, regardless of whether
* it's already in use by another filestream.
*/
if (max_ag != NULLAGNUMBER) {
xfs_filestream_get_ag(mp, max_ag);
free = maxfree;
*agp = max_ag;
break;
}
/* take AG 0 if none matched */
trace_xfs_filestream_pick(ip, *agp, free, nscan);
*agp = 0;
return 0;
}
trace_xfs_filestream_pick(ip, *agp, free, nscan);
if (*agp == NULLAGNUMBER)
return 0;
err = -ENOMEM;
item = kmem_alloc(sizeof(*item), KM_MAYFAIL);
if (!item)
goto out_put_ag;
item->ag = *agp;
item->ip = ip;
err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
if (err) {
if (err == -EEXIST)
err = 0;
goto out_free_item;
}
return 0;
out_free_item:
kmem_free(item);
out_put_ag:
xfs_filestream_put_ag(mp, *agp);
return err;
}
static struct xfs_inode *
xfs_filestream_get_parent(
struct xfs_inode *ip)
{
struct inode *inode = VFS_I(ip), *dir = NULL;
struct dentry *dentry, *parent;
dentry = d_find_alias(inode);
if (!dentry)
goto out;
parent = dget_parent(dentry);
if (!parent)
goto out_dput;
dir = igrab(d_inode(parent));
dput(parent);
out_dput:
dput(dentry);
out:
return dir ? XFS_I(dir) : NULL;
}
/*
* Find the right allocation group for a file, either by finding an
* existing file stream or creating a new one.
*
* Returns NULLAGNUMBER in case of an error.
*/
xfs_agnumber_t
xfs_filestream_lookup_ag(
struct xfs_inode *ip)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_inode *pip = NULL;
xfs_agnumber_t startag, ag = NULLAGNUMBER;
struct xfs_mru_cache_elem *mru;
ASSERT(S_ISREG(ip->i_d.di_mode));
pip = xfs_filestream_get_parent(ip);
if (!pip)
return NULLAGNUMBER;
mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
if (mru) {
ag = container_of(mru, struct xfs_fstrm_item, mru)->ag;
xfs_mru_cache_done(mp->m_filestream);
trace_xfs_filestream_lookup(ip, ag);
goto out;
}
/*
* Set the starting AG using the rotor for inode32, otherwise
* use the directory inode's AG.
*/
if (mp->m_flags & XFS_MOUNT_32BITINODES) {
xfs_agnumber_t rotorstep = xfs_rotorstep;
startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount;
mp->m_agfrotor = (mp->m_agfrotor + 1) %
(mp->m_sb.sb_agcount * rotorstep);
} else
startag = XFS_INO_TO_AGNO(mp, pip->i_ino);
if (xfs_filestream_pick_ag(pip, startag, &ag, 0, 0))
ag = NULLAGNUMBER;
out:
IRELE(pip);
return ag;
}
/*
* Pick a new allocation group for the current file and its file stream.
*
* This is called when the allocator can't find a suitable extent in the
* current AG, and we have to move the stream into a new AG with more space.
*/
int
xfs_filestream_new_ag(
struct xfs_bmalloca *ap,
xfs_agnumber_t *agp)
{
struct xfs_inode *ip = ap->ip, *pip;
struct xfs_mount *mp = ip->i_mount;
xfs_extlen_t minlen = ap->length;
xfs_agnumber_t startag = 0;
int flags, err = 0;
struct xfs_mru_cache_elem *mru;
*agp = NULLAGNUMBER;
pip = xfs_filestream_get_parent(ip);
if (!pip)
goto exit;
mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
if (mru) {
struct xfs_fstrm_item *item =
container_of(mru, struct xfs_fstrm_item, mru);
startag = (item->ag + 1) % mp->m_sb.sb_agcount;
}
flags = (ap->userdata ? XFS_PICK_USERDATA : 0) |
(ap->flist->xbf_low ? XFS_PICK_LOWSPACE : 0);
err = xfs_filestream_pick_ag(pip, startag, agp, flags, minlen);
/*
* Only free the item here so we skip over the old AG earlier.
*/
if (mru)
xfs_fstrm_free_func(mru);
IRELE(pip);
exit:
if (*agp == NULLAGNUMBER)
*agp = 0;
return err;
}
void
xfs_filestream_deassociate(
struct xfs_inode *ip)
{
xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
}
int
xfs_filestream_mount(
xfs_mount_t *mp)
{
/*
* The filestream timer tunable is currently fixed within the range of
* one second to four minutes, with five seconds being the default. The
* group count is somewhat arbitrary, but it'd be nice to adhere to the
* timer tunable to within about 10 percent. This requires at least 10
* groups.
*/
return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10,
10, xfs_fstrm_free_func);
}
void
xfs_filestream_unmount(
xfs_mount_t *mp)
{
xfs_mru_cache_destroy(mp->m_filestream);
}