/* * The global dirty threshold is normally equal to the global dirty limit, * except when the system suddenly allocates a lot of anonymous memory and * knocks down the global dirty threshold quickly, in which case the global * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
*/ #define DIRTY_SCOPE 8
struct backing_dev_info;
/* * fs/fs-writeback.c
*/ enum writeback_sync_modes {
WB_SYNC_NONE, /* Don't wait on anything */
WB_SYNC_ALL, /* Wait on every mapping */
};
/* * A control structure which tells the writeback code what to do. These are * always on the stack, and hence need no locking. They are always initialised * in a manner such that unspecified fields are set to zero.
*/ struct writeback_control { /* public fields that can be set and/or consumed by the caller: */ long nr_to_write; /* Write this many pages, and decrement
this for each page written */ long pages_skipped; /* Pages which were not written */
/* * For a_ops->writepages(): if start or end are non-zero then this is * a hint that the filesystem need only write out the pages inside that * byterange. The byte at `end' is included in the writeout request.
*/
loff_t range_start;
loff_t range_end;
/* * When writeback IOs are bounced through async layers, only the * initial synchronous phase should be accounted towards inode * cgroup ownership arbitration to avoid confusion. Later stages * can set the following flag to disable the accounting.
*/ unsigned no_cgroup_owner:1;
/* internal fields used by the ->writepages implementation: */ struct folio_batch fbatch;
pgoff_t index; int saved_err;
#ifdef CONFIG_CGROUP_WRITEBACK struct bdi_writeback *wb; /* wb this writeback is issued under */ struct inode *inode; /* inode being written out */
/* foreign inode detection, see wbc_detach_inode() */ int wb_id; /* current wb id */ int wb_lcand_id; /* last foreign candidate wb id */ int wb_tcand_id; /* this foreign candidate wb id */
size_t wb_bytes; /* bytes written by current wb */
size_t wb_lcand_bytes; /* bytes written by last candidate */
size_t wb_tcand_bytes; /* bytes written by this candidate */ #endif
};
/* * A wb_domain represents a domain that wb's (bdi_writeback's) belong to * and are measured against each other in. There always is one global * domain, global_wb_domain, that every wb in the system is a member of. * This allows measuring the relative bandwidth of each wb to distribute * dirtyable memory accordingly.
*/ struct wb_domain {
spinlock_t lock;
/* * Scale the writeback cache size proportional to the relative * writeout speed. * * We do this by keeping a floating proportion between BDIs, based * on page writeback completions [end_page_writeback()]. Those * devices that write out pages fastest will get the larger share, * while the slower will get a smaller share. * * We use page writeout completions because we are interested in * getting rid of dirty pages. Having them written out is the * primary goal. * * We introduce a concept of time, a period over which we measure * these events, because demand can/will vary over time. The length * of this period itself is measured in page writeback completions.
*/ struct fprop_global completions; struct timer_list period_timer; /* timer for aging of completions */ unsignedlong period_time;
/* * The dirtyable memory and dirty threshold could be suddenly * knocked down by a large amount (eg. on the startup of KVM in a * swapless system). This may throw the system into deep dirty * exceeded state and throttle heavy/light dirtiers alike. To * retain good responsiveness, maintain global_dirty_limit for * tracking slowly down to the knocked down dirty threshold. * * Both fields are protected by ->lock.
*/ unsignedlong dirty_limit_tstamp; unsignedlong dirty_limit;
};
/** * wb_domain_size_changed - memory available to a wb_domain has changed * @dom: wb_domain of interest * * This function should be called when the amount of memory available to * @dom has changed. It resets @dom's dirty limit parameters to prevent * the past values which don't match the current configuration from skewing * dirty throttling. Without this, when memory size of a wb_domain is * greatly reduced, the dirty throttling logic may allow too many pages to * be dirtied leading to consecutive unnecessary OOMs and may get stuck in * that situation.
*/ staticinlinevoid wb_domain_size_changed(struct wb_domain *dom)
{
spin_lock(&dom->lock);
dom->dirty_limit_tstamp = jiffies;
dom->dirty_limit = 0;
spin_unlock(&dom->lock);
}
/** * inode_attach_wb - associate an inode with its wb * @inode: inode of interest * @folio: folio being dirtied (may be NULL) * * If @inode doesn't have its wb, associate it with the wb matching the * memcg of @folio or, if @folio is NULL, %current. May be called w/ or w/o * @inode->i_lock.
*/ staticinlinevoid inode_attach_wb(struct inode *inode, struct folio *folio)
{ if (!inode->i_wb)
__inode_attach_wb(inode, folio);
}
/** * inode_detach_wb - disassociate an inode from its wb * @inode: inode of interest * * @inode is being freed. Detach from its wb.
*/ staticinlinevoid inode_detach_wb(struct inode *inode)
{ if (inode->i_wb) {
WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
wb_put(inode->i_wb);
inode->i_wb = NULL;
}
}
/** * wbc_init_bio - writeback specific initializtion of bio * @wbc: writeback_control for the writeback in progress * @bio: bio to be initialized * * @bio is a part of the writeback in progress controlled by @wbc. Perform * writeback specific initialization. This is used to apply the cgroup * writeback context. Must be called after the bio has been associated with * a device.
*/ staticinlinevoid wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
{ /* * pageout() path doesn't attach @wbc to the inode being written * out. This is intentional as we don't want the function to block * behind a slow cgroup. Ultimately, we want pageout() to kick off * regular writeback instead of writing things out itself.
*/ if (wbc->wb)
bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
}
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