1 files changed, 427 insertions, 0 deletions
diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
new file mode 100644
index 000000000..182501373
--- /dev/null
+++ b/fs/xfs/xfs_filestream.c
@@ -0,0 +1,427 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2006-2007 Silicon Graphics, Inc.
+ * Copyright (c) 2014 Christoph Hellwig.
+ * All Rights Reserved.
+ */
+#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_defer.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"
+#include "xfs_ag_resv.h"
+#include "xfs_trans.h"
+#include "xfs_shared.h"
+
+struct xfs_fstrm_item {
+	struct xfs_mru_cache_elem	mru;
+	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(
+	void			*data,
+	struct xfs_mru_cache_elem *mru)
+{
+	struct xfs_mount	*mp = data;
+	struct xfs_fstrm_item	*item =
+		container_of(mru, struct xfs_fstrm_item, mru);
+
+	xfs_filestream_put_ag(mp, item->ag);
+	trace_xfs_filestream_free(mp, mru->key, 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(VFS_I(ip)->i_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(mp, ip->i_ino, 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(pag,
+				xfs_alloc_min_freelist(mp, pag),
+				xfs_ag_resv_needed(pag, XFS_AG_RESV_NONE));
+		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;
+
+	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(VFS_I(ip)->i_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(mp, ip->i_ino, 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:
+	xfs_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 = 0;
+	int			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;
+	}
+
+	if (xfs_alloc_is_userdata(ap->datatype))
+		flags |= XFS_PICK_USERDATA;
+	if (ap->tp->t_flags & XFS_TRANS_LOWMODE)
+		flags |= XFS_PICK_LOWSPACE;
+
+	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(mp, mru);
+
+	xfs_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, mp,
+			xfs_fstrm_centisecs * 10, 10, xfs_fstrm_free_func);
+}
+
+void
+xfs_filestream_unmount(
+	xfs_mount_t	*mp)
+{
+	xfs_mru_cache_destroy(mp->m_filestream);
+}