--- /dev/null
+/*
+ * 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);
+ 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);
+}
Code Review / kvmfornfv.git / blobdiff